Posts Tagged ‘strawberry’

Strawberry IPM Newsletter No. 3 – June 1, 2012

Friday, June 1st, 2012

Strawberries

For full page print version, please see link at the bottom.

EARLY FRUIT NOW RIPENING

Insect Pressure Light; More Rain Ahead: Protect for Gray Mold

Note:  Twilight Meeting on June 5 at 5:30 p.m. at Stutzman’s Farm in Sangerville

Situation:  Heavy rains limited how many fields we could scout this week, but we managed to visit strawberry fields in Monmouth, New Gloucester, Minot, Lewiston, Wales, and Livermore Falls.  Early varieties are mostly past bloom, with some pink fruit showing.  Day neutral varieties grown on plastic mulch are now starting to be harvested.  Later varieties are in full to late bloom.  It is still looking like an early start to the season, although the cool, wet weather forecast for the next week will likely slow things down.  Growers will need to continue protecting blossoms and fruit from gray mold infection and be on the lookout for leather rot or anthracnose fruit rot because of all the recent rainfall.

Strawberry bud weevil or “clipper”:  Nearly all fields we visited are well beyond the stage at which clipper can do significant harm, although clipper was still present and active in some fields.  Northern fields may still have late varieties with susceptible flower buds, in which case scouting for damage should continue.  Remember that clipper will also damage raspberry and blackberry flower buds.  We have seen clippers in most raspberry plantings that we’ve been through this week.

Clipper Injury

Tarnished plant bugs were found in some of the fields scouted this week.  We found adults and small nymphs, but numbers were generally low, probably due to all the rain, which can slow their development and activity.  Keep scouting for the nymphs, because they may appear quickly when things dry out, and the feeding remains a threat even past petal fall.

First Instar Tarnished Plant Bug Nymph

First Instar Tarnished Plant Bug Nymph, Photo by David Handley

Two-spotted spider mites have been found in more fields and in higher numbers this week, although none of the fields have reached the threshold of 25% or more of leaves infested.  Mite development has probably been hindered by recent rainfall, but expect populations to increase rapidly once conditions become warmer and drier.

Two-spotted Spider Mites

Two-spotted Spider Mites, photo by Michigan State University

Cyclamen mites:  We found cyclamen mites in two more fields this week, with some plants showing fairly severe leaf crinkling and yellow streaking.  The symptoms can be mistaken for herbicide injury.  If you suspect your plants have cyclamen mites, give us a call or send us a plant sample (whole plant) for analysis.

Spittlebugs:  We have found a few spittlebug masses in fields this week.  Frothy spittle masses on the leaf and flower stems usually show up around bloom.  Spittlebugs don’t pose a significant threat to the plants, but the spittle masses are a nuisance for the pickers.  Spittlebugs overwinter as eggs and the nymphs emerge in late May.  Scouting for spittlebugs should start when the plants are at 10% bloom.  Randomly inspect five, one square foot areas per field every week.  Spread the leaves and inspect the crowns, leaf bases, leaf stems, and flower stems looking for the frothy spittle masses.  Small, yellow-orange nymphs will be under the spittle.  If the average number of spittle masses is more than two per foot, a treatment may be warranted.  Spittlebugs tend to be a greater problem in weedy fields. Pesticides currently registered for spittlebug control include Provado®, Thionex®, Danitol® and Brigade®.

Spittlebug

Spittlebug, photo by David Handley

Diseases:  Most fields have now had at least one fungicide spray to protect blossoms against gray mold.  If it has been more than a week since the last application or more than one inch of rain has fallen on the field, another spray should be applied soon.  Two to three sprays of fungicide are usually needed during bloom to provide adequate control of gray mold, but when rainfall exceeds one inch between sprays additional coverage is needed.  However, when conditions are dry after the second spray, further applications are often not necessary.

Gray Mold on Strawberries

Gray Mold on Strawberries, photo by James Dill

Leather rot (Phytopthora cactorum) continues to be a threat this spring because many fields have experienced extended periods with standing water between the rows.  These conditions are very conducive to the development of leather rot.  Foliar sprays during bloom and fruit development of Aliette®, Agri-Phos® or Phostrol® can provide good control of this disease.

Powdery mildew:  No severe symptoms of powdery mildew have been observed yet, but we’re starting to see a little more leaf rolling in fields suggesting that this disease may become more evident once temperatures start to rise.  Upward cupping of the leaves and reddish streaking or lesions on the leaf and flower stems are the most obvious symptoms of this disease.  White, powdery growth on the undersides of the leaves will appear as the disease develops further.

Anthracnose fruit rot remains a threat due to the recent wet weather and warm temperatures; especially for plantings using plastic mulch, which provides a good environment for the development and spread of the fungus.  Effective fungicides include Cabrio® and Abound®.

How much nitrogen fertilizer should I use?
Nitrogen is an essential component in the synthesis of amino acids and proteins in the plant.  As a fertilizer, it stimulates vegetative growth, such as leaves, petioles and shoots.  Heavy applications are not recommended in the springtime because excess vegetative growth at this time will result in dense leaf canopy that will cover developing fruit, keeping it in a dark, cool wet micro-climate, and encouraging the development of fruit rot such as gray mold.  In a matted row system, the majority of nitrogen fertilizer should be applied during the summer months, following harvest when new leaf and shoot (runner) growth is needed to re-establish good planting vigor for next year’s crop.

During the planting year (assuming the general fertility and condition of the soil is good), a strawberry planting should receive 20 to 40 pounds of actual nitrogen per acre incorporated into the soil prior to planting.  Another 30 pounds should be applied in late June to early July, and a final 20 pounds can be applied in late August to early September.  Each of these applications corresponds to periods of growth in the plants.  Calcium nitrate [Ca(NO3)2, 15% N] is the recommended source of nitrogen in new plantings because it is readily available, not volatile, and also provides calcium.

For established beds, only 10-20 pounds of actual nitrogen, if any, should be applied in the spring.  As part of the renovation process following harvest, 50 to 70 pounds of nitrogen per acre should be applied to the planting, followed by 20 to 30 pounds in late August to early September.  Recent studies have shown that this later summer application of nitrogen has significant positive impact on yield and growth the following year, so be sure not to forget it as the summer starts to wane.

Vegetable & Berry Growers Twilight Meeting
We hope to see you next Tuesday night, June 5th, 5:30 p.m. at Stutzman’s Farm, 891 Douty Hill Road in Sangerville for a growers twilight meeting and tour of this innovative farm.  Hold the date!

Sincerely,

David T. Handley
Vegetable & Small Fruit Specialist

Highmoor Farm                                  Pest Management
P.O. Box179                                      491 College Ave
Monmouth,ME 04259                       Orono,ME 04473
207.933.2100                                    1.800.287.0279

Maine Cooperative Extension, the Land Grant University of the state of Maine and the U.S. Department of Agriculture Cooperating.  Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment.  A Member of the University of Maine System.

Any person with a disability who needs accommodations for this program should contact Pam St. Peter at 207.933.2100 or TDD 1.800.287.8957 to discuss their needs at least 7 days in advance.

Where brand names or company names are used it is for the reader’s information.  No endorsement is implied nor is any discrimination intended against other products with similar ingredients.  Always consult product labels for rates, application instructions and safety precautions.  Users of these products assume all associated risks.

 

 

 

Strawberry IPM Newsletter No. 2 – May 25, 2012

Friday, May 25th, 2012

Strawberries

For full page print version, please see link at the bottom.

EARLY BLOOM MEANS EARLY CROP?

Clipper and Tarnished Plant Bug Active this Week; Time to Protect for Gray Mold

Note:  Twilight Meeting on June 5 at 5:30 p.m. at Stutzman’s Farm in Sangerville

Situation:  This week I visited strawberry fields in Monmouth, New Gloucester, Minot, Lewiston, Dresden, Livermore Falls, Farmington, Wells, Sanford, North Berwick, and Limington.  Fields in the southern region are generally past full bloom, while fields further north range from early to full bloom.  If the weather holds in a warm pattern, we could be looking at a very early harvest season.  Most fields have seen plenty of rain this week, and growers need to be protecting blossoms and fruit from gray mold infection if it has been more than a week since the last fungicide application.

Strawberry bud weevil or “clipper”:  Although clipper was both present and active in most fields this week, strawberries in the southern part of the state are beyond the stage at which clipper can do significant harm.  Fields further north that still have plants in the flower bud to early bloom stage should be on the lookout for clipper damage and be ready to apply a spray if the damage exceeds the spray threshold of more than one clipped bud per two feet of row length.  Growers should be aware that clipper will also damage raspberry flower buds, especially in years like this when the strawberry buds open early and deprive them of egg laying sites.

Clipper on Strawberry

Clipper on Strawberry, photo by David Handley

Tarnished plant bugs were found in most fields visited this week.  Small, green first instar nymphs are now showing up on blossoms, and overwintering adults are still feeding and laying eggs.  It is important to scout for the nymphs often, as they can show up quickly in warm weather.  For control options, review last week’s issue of this letter or see the 2010-2011 New England Small Fruit Pest Management Guide.

Tarnished Plant Bug Nymph on Strawberry Blossom

Tarnished Plant Bug on Strawberry

Two-spotted spider mites have only been found in a few fields this week, mostly along border rows on older leaves.  None of the fields scouted were over the threshold of 25% or more of leaves infested.  Mites tend to exhibit little growth under wet conditions, so our recent weather has probably kept them in check.  Overwintering adults are now laying eggs and we will start seeing more mites once we get a stretch of warm, dry weather.

Cyclamen mites:  We have seen some plants showing the stunting and crinkled leaves characteristic of cyclamen mite damage.  This has been a problem for some fields during the past two years.  Miticides such as Portal® or Thionex® can offer control, but they must be applied with lots of water (100-200 gals/acre) and a surfactant to get the materials deep into the crown where these very small mites reside.  We will continue to keep a lookout for this pest as it may become more prevalent as the temperatures start to rise.

Cyclamen Mite

Cyclamen Mite Damage on Strawberry Plant, photo by David Handley

White grubs:  We continue to find white grubs feeding on roots under the plants in weak looking fields.  It’s probably too late to successfully control them this spring, but a late summer/early fall soil drench with Admire® or an application of grub killing nematodes could prevent further infestation this fall.  These grubs are the larvae of beetles, most likely Japanese beetles, European chafers or Asiatic garden beetles.  You can scout for grubs by pulling up weak plants and sifting through the soil that surrounded the roots.

White Grub Under Strawberry

White Grub Under Strawberry Plant, photo by David Handley

Diseases:  Many fields have already received a fungicide spray to protect early blossoms from spores of Botrytis cinerea, the fungus that causes gray mold.  If it has been more than a week since the initial application, a second spray should be applied soon.  If the field is just coming into bloom and no fungicide has been applied, now is the time.  Two to three sprays of fungicide during bloom are required to provide good protection against this disease, but if rainfall exceeds more than one inch between sprays and wet conditions are prevalent, additional sprays may be required.  Alternatively, if conditions remain very dry after the second spray, then a third spray may not be necessary.

Leather rot (Phytopthora cactorum) is a threat if you have had wet conditions during bloom, especially if there has been standing water in the field.  Foliar sprays of Aliette®, Agri-Phos® or Phostrol® can provide control.  Sprays should be applied during bloom and fruit development.

Powdery mildew:  No severe symptoms of powdery mildew have been observed yet, but expect to see the problem become more noticeable under warmer, dry conditions.  Look for upward cupping of the leaves and reddish streaking or lesions on the leaf and flower stems.  Consider using a fungicide that will control powdery mildew, such as captan + Topsin-M®, or Pristine® when spraying for gray mold.

Powdery Mildew

Powdery Mildew, photo by David Handley

Anthracnose fruit rot is a potential problem for growers in the coming days as fruit ripens in fields that are wet from irrigation or rain.  This fungus is favored by warm, humid conditions and can spread rapidly during rains or frequent irrigation.  In cool seasons, it may appear close to harvest or may not show up at all.  Anthracnose fruit rot is identified by black sunken lesions with wet, orange (and sometimes gray) spore masses in them.  The anthracnose fungus can multiply on leaves without visible symptoms, which explains its sometimes sudden appearance in fields.  Fungicides such as Cabrio® and Abound® can provide good control of anthracnose fruit rot.

Anthracnose on Strawberry

Anthracnose on Strawberry, photo by North Carolina State University

Spotted wing drosophila (Drosophila suzukii) is a new pest which is likely to be a concern for late ripening strawberries, day neutral strawberries, fall raspberries and blueberries.  This is a small fruit fly, similar to the type that fly around the over ripe bananas in your kitchen.  However, this species will lay its eggs on fruit before it ripens, resulting in fruit that is contaminated with small white maggots just as it is ready to pick.  As a result, the fruit quickly rots and has no shelf life.  This insect recently came into the U.S.from northern Asia, and caused problems with many berry crops up the east coast last year.  It can complete a generation in under two weeks, with each adult female laying hundreds of eggs.  Therefore, millions of flies can be present soon after the introduction of just a few into a field.  This makes them very difficult to control, and frequently repeated insecticide sprays (3 to 5 times per week) have been needed to prevent infestations once the insect is established in a field.  It is likely that spotted winged drosophila can successfully over winter here, but we suspect that it may not build up to damaging levels until late in the summer.  This could mean that June bearing strawberries will not face a significant threat from it, but later ripening fruit such as day-neutral strawberries, raspberries and blueberries will probably need to be protected.  We will be setting out monitoring traps for spotted winged drosophila in fruit plantings around the state this spring to gather as much information on it as we can, and determine how much of a threat this pest will pose for fruit in Maine.  This will help us develop management strategies for the coming years.  For more information on this new and important pest, and to find instructions on making a simple monitoring trap, and how to identify this from other fruit flies, visit Michigan State University’s Spotted Wing Drosophila website.

Twilight Meeting Reminder:  June 5th, 5:30 p.m. at Stutzman’s Farm, 891 Douty Hill Road in Sangerville. Hold the date!

Sincerely,

David T. Handley
Vegetable & Small Fruit Specialist

Highmoor Farm                                  PestManagement
P.O. Box179                                      491 College Ave
Monmouth,ME 04259                       Orono,ME 04473
207.933.2100                                    1.800.287.0279

Maine Cooperative Extension, the Land Grant University of the state of Maine and the U.S. Department of Agriculture Cooperating.  Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment.  A Member of the University of Maine System.

Where brand names are used it is for the reader’s information.  No endorsement is implied nor is any discrimination intended against products with similar ingredients.  Always consult product label for rates, application instructions and safety precautions.  Users of these products assume all associated risks.

Any person with a disability who needs accommodations for this program should contact Pam St. Peter at 207.933.2100 or TDD 1.800.287.8957 to discuss their needs at least 7 days in advance.

Strawberry IPM Newsletter No. 1 – May 16, 2012

Wednesday, May 16th, 2012

Strawberries

For full page print version, please see link at the bottom.

2012 STRAWBERRY PEST MANAGEMENT SEASON BEGINS

Fighting Frost and Fungi

Note:   Twilight Meeting on June 5 at 5:30 p.m. at Stutzman’s Farm in Sangerville 

An early warm up in March and April got strawberry growth off to an early start, especially in fields that weren’t covered with straw.  However, the trend reversed itself later and growers found themselves protecting buds and flowers from frost much earlier than usual.  More recent cool, damp weather has slowed strawberry development, resulting in an extended bloom period.  This stretch of wet weather may help keep spider mites and tarnished plant bugs in check, at least temporarily, as these pests tend to have less success reproducing under cool, wet conditions.  However, gray mold, caused by the fungus Botrytis, and bacterial angular leaf spot can develop quite well under these conditions, and growers should be ready to apply preventative sprays as soon as possible.  We will start scouting strawberry fields for major insect pests in earnest next week, including volunteer farms, in North Berwick, Wells, Cape Elizabeth, PolandSpring, New Gloucester, Dresden, Monmouth, Wayne, and Farmington, and will be reporting our findings through this newsletter on a weekly basis until harvest time.  You can also get quick access to this information on the Pest Management web page at http://umaine.edu/ipm/.  If you would prefer to receive this message via e-mail, please give us a call at 933.2100 or send an e-mail message to:  pamela.stpeter@maine.edu.

The best way to manage strawberry pests is to scout your own fields regularly and often.  Start now, if you haven’t already.  You should be able to identify the major pests and their damage, and be able to determine if control measures are necessary.  To properly scout your fields you may want a copy of the Strawberry Production Guide for the Northeast, Midwest and Eastern Canada.  This contains detailed information on strawberry pest identification and monitoring, and also provides information on all other aspects of strawberry production.  It may be purchased for $45.00 per copy from the University of Maine Cooperative Extension.   You should also have a copy of the 2010-2011 New England Small Fruit Pest Management Guide, which contains the latest information on management control options for the major strawberry pests as well as scouting information.  Color pictures of the important strawberry pests are now also printed in the 2012-2013 New England Vegetable Management Guide.  Call or e-mail us if you are interested in purchasing copies of these guides.

Situation:  Early varieties are now showing some king blossoms in southern and mid-state fields.  Plants that weren’t mulched or that had row covers over them are moving into full bloom or beyond.  Development should speed up with some warm, dry days.  We have seen some indication of winter injury in some fields, which is not surprising, given the past winter’s lack of snow cover and fluctuating temperatures.  Frost injury is evident in early flowering varieties caught in the April freeze experienced in most of the state.  There is a threat of frost injury for at least another two weeks, so pay close attention to weather reports and be ready to protect the buds and blossoms should the temperature dip below freezing.  Bear in mind that fields that are irrigated for frost repeatedly during bloom face an increased risk of bacterial angular leaf spot.

Frost Injury

Frost Injury, photo by David Handley

Strawberry bud weevil or “clipper” is becoming active in fields this week.  I spotted a few weevils and just a little feeding damage in three different locations.  Expect these insects to become more active soon as temperatures rise and more flower buds emerge.  The clipper is a small weevil, which girdles strawberry flower buds, causing them to dry up and fall off the flower stalk.  Scout for damage by counting the number of clipped buds in two feet of row length at five different locations in a field.  If the average number of clipped buds per two-foot sample exceeds 1.2, or if live clippers are found, control measures are recommended.  Damage is usually first noticed at the edges of the field.  Border sprays may be effective in keeping this insect from becoming a problem in larger fields.  Fields with a history of clipper problems will typically exceed threshold nearly every year.  Insecticide options for clipper include Lorsban®, Brigade®, Sevin® and PyGanic®.

Clipper Beetle on Strawberry Bud

Tarnished plant bugs adults have been seen on strawberry flowers this week, but the damp weather may have reduced their egg-laying success, as I have not found any nymphs (immature stages) yet.  Once the eggs start to hatch, we’ll find the nymphs feeding in the flowers.  The nymphs are small, active, yellow-green insects.  It is important to scout for them regularly, as they can appear very quickly in warm weather.  Tarnished plant bugs feed on the open strawberry flowers, causing the berries to have seedy ends.  To scout for the nymphs shake 30 flower clusters (six clusters in five different locations) over a plate.  If four or more of the clusters out of the 30 sampled have any nymphs, control measures should be taken.  Be on the alert and scout your fields now!  Insecticide options for tarnished plant bug include malathion, Brigade®, Danitol®, Thionex® and PyGanic®.

Tarnished Plant Bug Adult

Tarnished Plant Bug Adult, photo by David Handley

Cyclamen mites:  Plants showing weak growth and yellow, pinkish or blackened, crinkled leaves may be infested with cyclamen mite.  Cyclamen mites are very small, smaller than spider mites, and reside in the crown of the strawberry plant feeding on the developing leaves and flower buds.  They are very hard to see, even with magnification.  Infested plants have shrunken distorted leaves and flower stalks, and produce few, if any, marketable fruit.  Miticides such as Thionex® or Kelthane® and Temprano® can be effective, but must be applied in lots of water to be sure that the material is carried down into the crowns where these mites reside.  I haven’t found live cyclamen mites yet, but many fields were infested last year, so be on the look out for these symptoms.

Cyclamen Mite

Cyclamen Mite Damage on Strawberry Plant, photo by David Handley

Two-spotted spider mites have not yet been a problem this spring, but growers with plants under row covers should be alert.  This is often where we first find mite problems.  Spider mites will reproduce rapidly when warmer weather arrives, so it is important to scout for them regularly.  Spider mites feed on the undersides of strawberry leaves, rasping the plant tissue and sucking the sap.  Infested leaves will develop yellow flecking and a bronzed appearance.  The plants become weakened and stunted.  Fields that have had excessive nitrogen fertilizer and/or row covers tend to be most susceptible to mite injury.  To scout for mites, collect 60 leaves from various locations in the field and examine the undersides for the presence of mites.  Mites are very small – you may need a hand lens to see them.  Chemical control options for two-spotted spider mites include Acramite®, Savey®, Zeal®, Vendex®, Oberon®, Brigade®, Danitol®, Thionex® and JMS Stylet oil ® (oils will cause plant injury if used in combination with captan or within 14 days of an application of sulfur).

Two-spotted Spider Mites

Two-spotted Spider Mites, photo by Michigan State University

Root weevil management
Given the relatively mild winter we should expect good survival of strawberry root weevil and black vine weevil in fields that were previously infested.  Infested plants appear week and stunted, usually in somewhat circular patches in a field.  Digging under the plants will reveal small (1/4″-1/2”) crescent-shaped legless grubs.  Typically, the grubs begin to pupate when the plants are in bloom, but we have seen both small grubs and pupae already this spring.  A soil drench of Platinum® (thiamethoxam) insecticide during the spring and/or fall when the grubs are active in the soil can provide control.  However, Platinum® has a 50 day pre-harvest interval, so it is too late for applications in most fruiting fields this year.  Platinum® may also be used as a pre-plant or planting treatment for root weevils.  It is not too late to put on an application of nematodes to control the grubs (optimal timing is about mid-May).  Two species of nematodes appear to offer the best control of root weevil grubs.  Heterorhabditis bacteriophora (Hb) appears to be the best candidate for control of root weevils when the soil temperature is above 60 degrees (‘J-3 Max Hb’ from The Green Spot Ltd., http://greenmethods.com/site/; ‘GrubStake Hb’ from the Integrated Biocontrol Network, http://www.biconet.com/;  ’Larvanem’ from Koppert Biological Systems, http://www.koppertonline.com/).

Strawberry Root Weevil Grub

Strawberry Root Weevil Grub, photo by David Handley

Nematodes are living organisms and they can be killed if they are misapplied.  Order nematodes ahead of time and be ready to apply them through a sprayer or irrigation soon after they arrive, refrigerating if delay is necessary.  Do not apply nematodes using a sprayer with a piston pump.  Use clean equipment, removing all screens finer than 50-mesh.  Apply nematodes in early morning or evening in a high volume of water to already moist soil, pre-irrigating if needed.  Apply another ¼ inch of irrigation after application to wash them onto and into the soil.  Researchers and suppliers recommended 250 (if banded in the row) to 500 million per acre, at a cost of about $100 per 200 acres depending on volume and source.  Ironically, nematodes probably work best in the worst weevil-infested fields.  High populations of weevil larvae allow explosive growth in nematode populations, while low populations of larvae may not permit efficient nematode reproduction.  Strawberry plants can recover their vigor remarkably well if crown feeding has not occurred and diseases haven’t taken over the roots.

Once the adults become active in July, bifenthrin (Brigade®) will provide some control if used at the highest labeled rates.  The best timing for this spray is at night during the peak feeding activity of adults, before they start laying eggs, or about the time harvest ends.

White Grubs:  Weak growth noted in several fields this spring appears to be the result of white grubs feeding on the roots of newer plantings.  These grubs are the larvae of beetles, most likely European chafer or Asiatic garden beetle.  They differ from the larvae of black vine weevil and strawberry root weevil in that they have legs and a swollen anterior (rear end), and they tend to be larger.  Their feeding weakens the plants by reducing the number of roots.  The grubs can be found by pulling up weak plants and sifting through the soil that surrounded the roots.   Controlling white grubs once they have become established in a field can be difficult.  These tend to be more of a problem in new fields that have been planted following a grass rotation crop, because the adults prefer to lay their eggs in sod.  Admire®  insecticide is labeled for control of white grubs.  It should be applied within two hours of irrigation or rainfall to be sure it gets into the root zone.  It requires a 14 day to harvest interval.

White Grub

White Grub, Photo by David Handley

Slugs are likely to be a problem in some fields this season.  Moist conditions encourage the presence of these mollusks.  Slugs usually feed at night, leaving large holes and tunnels in ripening fruit.  Baits such as Deadline®  and Sluggo® offer some control of slugs, but should be used prior to fruit ripening.  Pay close attention to label instructions and precautions.  Baits should also be applied to the fields in mid-September if slugs have been a problem, to reduce egg-laying.

Diseases:  Bloom is a critical time to protect strawberry fruit against gray mold caused by the fungus Botrytis cinerea, especially when conditions have been damp.  Two to three sprays of fungicide during bloom are typically required to provide good protection against this disease.  If you tank mix insecticides and fungicides, avoid spraying when bees are active.  Botrytis cinerea overwinters on old leaves and plant debris.  Fruit infections take place almost exclusively through the flowers, so gray mold control efforts must be focused on the bloom period.  If the bloom period is dry and/or good fungicide coverage is maintained, incidence of gray mold at harvest should be low.

There are several excellent fungicide choices for control of gray mold in strawberries.  Elevate® (fenhexamid) has good to excellent activity against Botrytis. Captevate® is a pre-mix of captan and fenhexamid and has a broader spectrum of activity than Elevate® alone.  Switch® (cyprodinil and fludioxonil), Scala® (pyramethanil) and Pristine® (pyraclostrobin and boscalid) are also excellent products for gray mold control.  Topsin M® + captan is also a good fungicide combination, but remember that captan is strictly a protectant and can be washed off by rain or irrigation water. Thiram is similarly effective but also susceptible to wash-off.

The fungicides Cabrio® (pyraclostrobin) and Abound® (azoxystrobin) are NOT suitable for gray mold control, but are effective against anthracnose and other fruit rot and leaf spot diseases.  All fungicides mentioned above have a 0-day pre-harvest interval, except Topsin M® (1 day) and thiram (3 days). Remember to alternate fungicides with different modes of action for resistance management purposes.

Gray Mold on Strawberries

Gray Mold on Strawberries, photo by James Dill

Leather rot (Phytopthora cactorum) may also become an issue when you have a lot of water in the fields during bloom and fruit development, especially if you did not get mulch on the fields last fall and the plants are on bare, wet soil.  Leather rot is best controlled by growing strawberries in well-drained soil and applying straw mulch between the rows to prevent berries from touching the soil and reduce any soil from splashing up onto the berries.  Foliar sprays of Aliette®, Agri-Phos® or Phostrol® (similar to Aliette®) may also provide control.  Sprays should be applied during bloom and fruit development.

Red stele root rot
Although fall and early spring conditions were not especially conducive to red stele development, damp conditions this spring should make us alert for this root rot if any fields appear to be weak, stunted or dying.  To diagnose red stele, pull up a few plants that look weak and scrape the roots of these plants to see if the center of the root, known as the stele, is rusty red in color, instead of the normal white.  The red color would indicate an infection.  Red stele is caused by Phytophthora fragariae, a soil pathogen that infects roots when soils are wet with temperatures around 50°F.  The pathogen grows into the roots causing the plants to become weak, stunted and to eventually die.  Symptoms are most evident in the spring, and can be mistaken for winter injury. Ridomil Gold®, Alliette® or Phostrol® are fungicides that can be applied in the late fall or early spring for control of red stele.  Many varieties have some level of resistance to the disease, but the most effective management strategy is to plant only into well-drained soils, and/or plant onto raised beds.

Powdery mildew:  This fungus disease has been starting to show up as purple or red blotches on the leaf petioles and flower stems in some fields.  Most of us are more familiar with the later symptoms of upward curling of the leaves and white, powdery growth on the undersides of the leaves.  Check your fields for pinkish purple leaf and flower stem lesion symptoms now.  Abound®, captan, Pristine®, Cabrio®, Topsin-M® and JMS Stylet oil® are presently registered to control powdery mildew.

Powdery Mildew

Powdery Mildew, photo by David Handley

Angular leaf spot is a bacterial disease that is characterized by translucent leaf spots that may turn yellow and eventually black.  The symptoms tend to start on the lower leaves but may move upwards as bacterial spores are splashed up by rain or irrigation water. Infection of the calyxes may result in a blackening of the berry stems and caps, reducing their marketability.  Bacterial angular leaf spot is favored by extended cool, wet weather and nights with temperatures close to freezing.  Frequent irrigation for frost protection can greatly encourage the development and spread of the disease, as will extended cool, damp weather.  Susceptibility to this disease appears to vary significantly between varieties. Copper-containing chemicals, such as Kocide, Cuprofix, and Bordeaux are the only materials that have much effect on this disease.  Some labels suggest adding lime as a “safener” to reduce the risk of crop injury.  In susceptible varieties, start spray applications before bloom to prevent multiplication of the bacteria on the leaves before they jump to the berry caps.  Application of copper sprays after bloom can result in fruit injury and is not recommended.  Recent research suggests that hydrogen dioxide (OxiDate®) may also have some activity against angular leaf spot when used on strawberries as part of a gray mold management program.

Angular Leaf Spot

Bacterial Angular Leaf Spot, Photo by David Handley

Vegetable & Berry Grower Twilight Meeting on June 5
The University of Maine Cooperative Extension and the Maine Vegetable and Small Fruit Growers Association will hold a growers meeting at Stutzman’s Farm in Sangerville on Tuesday, June 5th at 5:30 p.m.  Sid and Rainie have operated the farm for nearly 30 years and produce a wide range of vegetables and fruit for their stand and CSA.  Sustainable practices have been an important part of their production strategy, and we’ll have an opportunity to see some of the work they have been doing with zone tillage, as well as new high tunnels, and their stand and bakery.  We will have an opportunity to discuss the strawberry season and pest situation and have an update on GAP certifications and new regulations.  We anticipate one pesticide applicator re-certification credit will be available for attending the meeting. Please join us!  Stutzman’s Farm is located at 891 Douty Hill Road in Sangerville. You can visit their website at:  http://www.mainehighlandsfarmers.com/StutzmansFarm.html.  We’ll provide more detailed directions in a future issue.

Sincerely,

David T. Handley
Vegetable & Small Fruit Specialist

Highmoor Farm                                  Pest Management
P.O. Box179                                      491 College Ave
Monmouth,ME 04259                         Orono, ME 04473
207.933.2100                                    1.800.287.0279

Maine Cooperative Extension, the Land Grant University of the state of Maine and the U.S. Department of Agriculture Cooperating.  Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment.  A Member of the University of Maine System.

Where brand names are used it is for the reader’s information.  No endorsement is implied nor is any discrimination intended against products with similar ingredients.  Always consult product label for rates, application instructions and safety precautions.  Users of these products assume all associated risks.

Any person with a disability who needs accommodations for this program should contact Pam St. Peter at 207.933.2100 or TDD 1.800.287.8957  to discuss their needs at least 7 days in advance.

Strawberry IPM Newsletter No. 6 – August 2, 2011

Wednesday, August 3rd, 2011

Strawberries

For full page print version, please see link at the bottom.

RENOVATION AND WEED MANAGEMENT ISSUE

Hot Weather Brings a Quick End to the Season

The strawberry season followed a more “normal” pattern this year, beginning about when we would typically expect, although shorter than we would like due to high temperatures; which led to early ripening of late varieties.  There were very few issues with frost this year, as most fields didn’t require protection at all through the bloom period.  Damage from tarnished plant bug, strawberry clipper and two-spotted spider mites was very light this spring.  Powdery mildew, cyclamen mites, and potato leafhoppers have been an issue in some fields, but overall growth and development have been good.  Thanks to some good weekend weather, the pick-your-own demand was good and sales at local stands and markets were strong.

There were some issues with post-emergent grass control this spring.  In several fields we saw many plants with leaves that were brown and drying up.  Looking at the spray records, these fields had received a post-emergent grass herbicide mixed with crop oil as recommended on the label.  It is important to note that if you apply any spray containing oil to your fields, you should not apply any fungicide containing captan for at least two weeks, or foliar injury is quite likely.  Foliar injury with oil sprays can also occur if very hot, humid weather follows the application, but captan was the likely cause in the fields we observed this spring.

Bed renovation should begin as soon after harvest as possible.  The earlier the beds get renovated, the more time runner plants have to develop, which means larger crowns and more flower buds for next year.  Early renovation also improves weed management by tilling in many weeds before they go to seed, and can help with insect and foliar disease control by interfering with life cycles at a critical stage of development.

Strawberry Bed Renovation Review
The first step in the bed renovation process is to determine which beds should be carried over for another year and which should be plowed down and put into a crop rotation.  Beds that did not suffer much from winter injury had good production and a good plant stand with no major weed, insect or disease problems should be carried over for another year.  Beds that do not meet these criteria should be plowed down and seeded to a suitable cover crop to reduce weed, insect and disease problems that have developed, and to increase soil organic matter content.  Ideally, beds that are plowed down should be rotated out of strawberries for at least three years.  If properly managed, crop rotation will greatly reduce pest problems and improve the vigor and longevity of strawberry beds without the need for soil fumigation.

Renovating a strawberry bed is basically a thinning process to promote healthy new growth that can support a good crop next spring.  While some parts of the following renovation scheme may need to be modified for individual situations, all beds should undergo the following steps once harvest is complete.

1.  Broadleaf weed control:  If perennial broadleaf weeds such as dandelion, shepherd’s purse, daisy or goldenrod are a problem and/or a high population of annual broadleaf weeds such as lambsquarters, sorrel or pigweed are present, hand-pull as many as possible, especially within the plant rows, and/or apply 2,4-D amine (Formula 40®).

2.  Leaf mowing:  Four to five days following the 2,4-D application (or immediately if 2,4-D was not applied) mow off the leaves of the strawberries about 1½ inches above the crowns.  If the planting is weak, it is recommended that this step of the renovation process be skipped.

Mowing Strawberry Leaves

Mowing Strawberry Leaves, photo by David Handley

 

3.  Fertilization:  Apply 40 to 60 pounds of actual nitrogen per acre (use the higher rate on sandy soils and fields where growth has been weak).  Phosphorus and potassium applications should be made according to soil test recommendations.  Soil testing kits and information are available from your county Cooperative Extension office.

10-10-10

10-10-10 Fertilizer, photo by David Handley

 

4.  Plant thinning:  For the single matted row system, strawberry plant rows should not be any wider than 24 inches.  After mowing off the leaves, till the sides of the rows to narrow the beds back to a width of 12 to 18 inches.  Use the wider setting for varieties that tend to throw few runners or any fields experiencing drought stress.    Set the tiller so that it incorporates the mowed leaves and spreads about one inch of soil over the remaining crowns at the same time.  This will reduce leaf disease and mite problems, and help stimulate new root growth on the remaining plants.

5.  Pre-emergent weed control:  To control annual weeds, apply terbacil (Sinbar® 80WP) according to label directions (2 to 6 oz. per acre).  Be sure to follow all label precautions. To avoid plant injury, do not use terbacil if you do not intend to mow off the leaves.  Napropamide (Devrinol®) or DCPA (Dacthal®) may be used as an alternative to terbacil at this time, as described below.  If you are not using herbicides, regular cultivation, before weeds are more than 2” tall, will be needed throughout the summer.

6.  Subsoiling:  Soil compaction caused by tractor and picker traffic in the field can cause soil drainage problems and interfere with good root development.  Using a subsoiling blade between the rows will break up compacted layers of soil and improve water infiltration.  Subsoiling is best done late in the renovation sequence to prevent interference from straw and crop residues.

7.  Irrigation:  To encourage rapid plant growth and get the most out of fertilizers and herbicides, irrigate the beds regularly.  Strawberries will grow best if they receive 1½ inches of water per week during the growing season.

Strawberry Irrigation

Strawberry Irrigation, photo by David Handley

 

Don’t forget your plants once these renovation steps are completed.  Check the strawberry fields regularly during the summer for pest problems.  Finding and managing problems early can prevent major problems next spring.  Pay close attention to the following items:

Nutrition:  Following the application of 40 to 60 pounds of actual nitrogen at renovation, another 20 pounds of nitrogen may be applied in mid- to late-August to stimulate flower bud development.  One way to determine the nutrient status of strawberry plants during the summer is to have a leaf tissue analysis done.  Tissue analysis offers a view of what is happening within the plant, and can spot any nutrient deficiencies.  In combination with regular soil tests, tissue analysis will provide a complete picture of a field’s fertilizer needs.  For more information about tissue analysis contact the Analytical Lab, 5722 Deering Hall, Rm. 407, University of Maine, Orono, ME 04469-5722, telephone: 581.2945.

Sidedressed Strawberry Planting

Sidedressed Strawberry Planting, photo by David Handley

 

Diseases:  Foliar diseases should be monitored in your fields by regularly examining leaves.  All of the common leaf diseases were present in fields this spring and we should expect that they will continue to be a problem through the summer.  The most common summer diseases are powdery mildew, leaf spot and leaf scorch.  Fungicides available for these diseases include captan, Topsin-M®, Cabrio®, Pristine® and Abound®.  See the 2010-2011 New England Small Fruit Pest Management Guide for detailed descriptions of these diseases and their management.

Leaf Scorch

Leaf Scorch, photo by David Handley

 

Insects:  If black vine weevils or strawberry root weevils are a problem in a strawberry field that you would like to carry over, bifenthrin (Brigade®) can be applied when adult feeding is noticed (usually until mid-late July).  Look for notching along the leaf edges and the presence of the black or brown snout beetles.  Applications should be made at night when these insects are active, and the highest rate of the insecticide should be used.  For control of the grubs a soil drench of Platinum® (thiamethoxam) insecticide should be applied during the fall and/or early spring when the grubs are active in the soil.  This product has a 50 day pre-harvest interval and may also be used as a pre-plant or planting treatment for root weevils.  Parasitic nematodes such as Heterorhabditis bacteriophora or Steinernema feltiae can also be applied to provide control of root weevil grubs in late August.  Nematodes require specialized handling and application.  Contact us or talk with one of the suppliers for more details.  See the 2010-2011 New England Small Fruit Pest Management Guide for sources.

Black Vine Weevil

Black Vine Weevil, photo by David Handley

 

Strawberry rootworm (not root weevil) is a small (1/8″) dark brown to black beetle which feeds on strawberry foliage, causing it to look skeletonized.  The small larvae feed on strawberry roots, further weakening the plant.  Adult feeding damage on the leaves usually occurs in late July through August.  Heavy rootworm feeding weakens strawberry plants so control is warranted when injury is noticed.

Strawberry Rootworm Beetle

Strawberry Rootworm Beetle, photo by James Dill

 

Keep a lookout for potato leafhoppers, which can weaken strawberry plants and spread disease.  The potato leafhopper does not overwinter in Maine, but must fly in from southern states.  These small, bullet-shaped insects feed on plant sap from the undersides of leaves, causing the leaves to become curled, stunted and yellow-streaked.  Symptoms are often first noticed in new strawberry plantings, but leafhoppers will also infest older plantings and a variety of vegetables, flowers and fruit crops.  To scout for leafhoppers, brush the leaves of the plants with your hand.  The small, whitish adults can be seen flying off the plant.  Examine the underside of some injured leaves.  Look for small, light green leafhopper nymphs.  They are about 1/16 inch long.  When touched, they will crawl sideways in a crab-like manner.  Controls for potato leafhoppers include malathion, carbaryl or Provado®.

Potato Leafhopper

Potato Leafhopper, photo by New York State Agricultural Experiment Station

 

hopperburn1

Leafhopper Burn, photo by David Handley

 

Mites:  Two-spotted spider mites can become problems during the summer.  Continue to take leaf samples for spider mites after renovation.  If more than 25% of a 60-leaf sample has mites, controls should be applied.  Summer is an ideal time to use predatory mites to control pest mites, because they prefer warm temperatures, and there is less chance of an insecticide spray that might kill them.  Amblyseius fallacis can provide good control of two-spotted spider mites when they are released at a rate of about 10,000 mites per acre.  Predator mite releases should only be made after a spider mite infestation has been found in the field.  Releasing predators into a clean field will often result in them dying, due to a lack of food.  See the 2010-2011 New England Small Fruit Pest Management Guide for sources of predatory mites.

Two-spotted Spider Mites

Two-spotted Spider Mites, photo by David Handley

 

 

Cyclamen mites:  Plants showing weak growth and yellow, crinkled leaves may be infested with cyclamen mite.  Cyclamen mites are very small and reside down in the crown of the strawberry plant feeding on the developing leaves.  They are very hard to see, even with magnification.  Miticides such as Thionex®, Kelthane® or Portal® can be effective, but must be applied in lots of water to be sure that the material is carried down into the crowns.  If you suspect you have this problem, give us a call.

Cyclamen Mite Damage

Cyclamen Mite Damage, photo by David Handley

 

Weeds:  Weeds can become a big problem during the summer because they are often forgotten among all the other demands on our time and because of limited control options.  However, the importance of good weed management should not be underestimated.  Keeping weeds under control this summer will prevent future infestations.  Here’s a summary of weed control options for strawberries:

1.  Cultivation:  Following renovation, cultivation between strawberry rows can provide effective temporary control of annual weeds.  Several types of cultivators are available which will work well in strawberry beds.  Cultivators can also be used to help sweep runners into the plant rows.

2.  DCPA (Dacthal®):  A pre-emergent herbicide used in the early spring, late fall or after renovation.  It offers good, short-term control of some annual broadleaf weeds and grasses.  It is weak on ragweed, galinsoga, smartweed, shepherd’s purse and mustard.  Its action will be improved if worked into the soil by irrigation or light cultivation, and it tends to work best in lighter, warmer soils.  This may be used as an alternative to terbacil or napropamide when there is a high risk of plant injury from those products.

3.  Napropamide (Devrinol®):  A pre-emergent herbicide which provides good control of annual grasses, volunteer grains and some broadleaf weeds.  It is typically applied just before mulching in the fall.  Split applications have become popular due to the loss of other pre-emergent herbicides, e.g. half maximum rate application after renovation or in late summer after desired daughter plants have rooted, and a second half rate application once the strawberry plants are dormant.  Napropamide should be activated by irrigation, rainfall or light cultivation within 24 hours of application.  Repeated long-term use of this material, i.e. with no crop rotation, may eventually result in poor daughter plant establishment, due to rooting inhibition.

4.  Terbacil (Sinbar®):  An effective pre-emergent herbicide with some post-emergent activity, which should be applied at renovation time – after mowing and tilling the beds, but before new growth begins.  A second application can be made in late fall, after the plants are dormant.  No more than 6 oz. may be applied in a single application, and no more than 8 oz. may be applied in one season.  An example of one season’s use could be 5 oz. applied at renovation and 3 oz. applied in the late fall, the latter in addition to napropamide or DCPA.  Terbacil can cause injury to strawberry plants.  It is important to determine appropriate rates for each location.

5.  Sethoxydim (Poast®):  A post-emergent herbicide for control of actively growing grasses.  It will not control broadleaf weeds.  It should not be applied when grasses are under stress, e.g. drought, or on unusually hot, humid days.  Do not use sethoxydim within six weeks of a terbacil (Sinbar®) application to avoid leaf injury.  Sethoxydim should be used in combination with a crop oil concentrate.  Do not tank mix with 2, 4-D.

6.  Clethodim (Arrow®, Prism®, Select®):  A post-emergent herbicide, similar in activity to Poast®, for control of actively growing grasses.  It will not control broadleaf weeds.  It should not be applied when grasses are under stress, e.g. drought, or on unusually hot, humid days.  Clethodim should be used in combination with a crop oil concentrate.

7.  Paraquat (Gramoxone Inteon®):  A contact herbicide for post-emergent control of most annual weeds and suppression of many perennial weeds.  Paraquat will injure or kill strawberries, so applications are made between rows only, with a sprayer shielded to protect the strawberries.  It should be used in combination with a nonionic surfactant.  Paraquat should not be applied within 21 days of harvest or more than three times in one season.

8.  Pelargonic Acid (Scythe®):  A contact herbicide for post-emergent control of most annual weeds and suppression of many perennial weeds.  Scythe® will injure or kill strawberries, so applications are made between rows only, with a sprayer shielded to protect the strawberries.  This product has a relatively low toxicity and no residual soil activity.  It has a strong, unpleasant odor.

9.  2,4-D amine (Formula 40, Amine 4):  A post-emergent herbicide effective on most broadleaf perennial weeds.  It will not control grasses, nor offer any pre-emergent control.  2,4-D should be applied immediately after harvest is complete if emerged broadleaf weeds are a problem.  After application, the bed should be left undisturbed for three to five days, before mowing the leaves off the plants.  This allows time for the material to be taken in by the weeds.  This material can also be used when the plants are dormant (late fall or early spring) to control winter annuals and biennials.  Such applications have been of minimal benefit in northern New England, and sometimes result in injury to the strawberries.  Do not tank mix 2,4-D with sethoxydim (Poast®).

10.  Flumloxazin (Chateau®):  A pre-emergent herbicide for control of broadleaf weeds, including dandelion and shepherd’s purse.  For use in the fall when plants are dormant for control of weeds the following spring.

11.  Pendimethalin (Prowl H20®):  A pre-emergent herbicide that may be applied as a band with a shielded sprayer between the rows of strawberries.  No weed control will be provided within the plant rows, and contact of this product on the strawberry plants will cause injury.  May not be applied within 35 days of harvest.

The use of herbicides alone rarely gives complete weed control. Some hand weeding will be necessary.  To provide good weed control throughout the life of a strawberry bed, growers should concentrate on crop rotation and good pre-plant weed control.

Pest Management for Day-Neutral Strawberries
As more growers try raising day-neutral strawberries to expand the local strawberry season and increase sales, it is important to note that some of the same pests that damage June-bearing varieties can be as much or more of a problem on day-neutral types.  Because day-neutral strawberries will have buds, flowers and fruit all occurring at the same time, it is critical to pay close attention to the required number of days to harvest after a specific pesticide application, to be sure you can safely harvest ripe fruit while still protecting buds and blossoms.  Some of the more important pests are listed below, along with currently recommended pesticides and days to harvest as stated on current labels.

Tarnished plant bug:  This is one of the most prevalent and persistent pests of day-neutral strawberries, as summer flowering coincides with peak populations of this insect.  Adult and nymph stages feed on the flowers and developing fruit, causing them to have seedy ends and other malformations.  Regular insecticide applications are often required to keep the damage in check.  Scout the flower clusters for adults and nymphs often to determine if controls are necessary.  Insecticide products for tarnished plant bug include:

Tarnished Plant Bug

Product Days to Harvest
Brigade® 0
Pyganic® 0
Assail® 1
Dibrom® 1
Rimon® 1
malathion 3
Thionex® 4

 

Large Tarnished Plant Bug Nymph

Third Instar Tarnished Plant Bug Nymph, photo by David Handley

 

 

Tarnished Plant Bug Injury on Strawberries

Tarnished Plant Bug Injury, Photo by David Handley

 

Two-spotted spider mites:  Mites can become a problem during the summer when the growing conditions are warm and dry.  In addition to infesting the leaves, mites can move onto the fruit, reducing marketability.  Plants that are drought-stressed, over fertilized with nitrogen, or prone to dust covering, e.g. growing beside a dirt road, are especially prone to mite infestation.  Predatory mites can be an effective means to control spider mites and keep them in check over the season.  Releases should only be made when spider mites are present in the field to provide the predators with a source of food.  Most of the products labeled for controlling spider mites will also kill predatory mites, so do not use these products after predators have been released.  Scout for mites often during the season by examining the undersides of the leaves.  Control is warranted if more the 25% of leaves examined have mites.

Two-Spotted Spider Mites

Product Days to Harvest
Brigade® 0
Zeal® 1
Vendex® 1
Acramite® 1
Danitol® 2
Agri-Mek® 2
Oberon® 3
Savey® 3
Kelthane® 3

 

Two-spotted Spider Mites

Two-spotted Spider Mites, photo by Michigan State University

 

 

Potato leafhoppers, sap beetles, thrips and spittlebugs may also become problems on day-neutral strawberries, but are less frequently observed than tarnished plant bug and spider mites.  Recommendations for these insects can be found in the current edition of the New England Small Fruit Pest Management Guide.

Foliar and fruit diseases also need to be managed on day-neutral strawberries, and should be controlled in much the same way as they are for June-bearing varieties.  Most of the fungicide products labeled to control gray mold, powdery mildew, leaf spot and leaf scorch have either zero or one day to harvest, so protecting blossoms  at the same time as fruit is near harvest should not be a problem; but be sure to check labels carefully and schedule your sprays and harvests accordingly.  Anthracnose fruit rot can be especially troublesome for day-neutral strawberries, because it grows well under warm conditions and spreads by splashing water, which is encouraged on plastic mulch.  Fungicides registered for control of anthracnose include Cabrio®, Abound®, Pristine® and Switch®, all of which have zero days to harvest restriction.

 

Anthracnose on Strawberry

Anthracnose on Strawberry, photo by North Carolina State University

 

Visit the 2010-2011 New England Small Fruit Pest Management Guide online for more detailed pest information.

Sincerely,

David T. Handley
Vegetable & Small Fruit Specialist

Highmoor Farm                      Pest Management
P.O. Box179                          491 College Avenue
Monmouth,ME 04259            Orono,ME 04473
207.933.2100                        1.800.287.0279

Where brand names are used it is for the reader’s information. No endorsement is implied nor is any discrimination intended against products with similar ingredients.  Always consult product label for rates, application instructions and safety precautions.  Users of these products assume all associated risks.

Published and distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914, by the University of Maine Cooperative Extension, the Land Grant University of the state of Maine and the U.S. Department of Agriculture Cooperating.  Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment.

 

Strawberry IPM Newsletter No. 5 – June 17, 2011

Monday, June 20th, 2011

 

Strawberries

For full page print version, please see link at the bottom.

HARVEST SEASON BEGINS WITH GREAT POTENTIAL

Root Weevils, Cyclamen Mites, Powdery Mildew Most Common Issues

Situation:  Southern fields will open in earnest this week, as we hope to see a stretch of nice weather to see us through the harvest.  The crop size and quality looks very good in most fields, except in the few where injury from root weevils has seriously reduced plant vigor.  Most fields are past the point where clipper or tarnished plant bug could cause injury, and scouting should focus on pests that attack ripe fruit, such as sap beetles, slugs, birds, and anthracnose fruit rot.  The Strawberry IPM Newsletter will take a couple of weeks off while we enjoy the harvest and will be back with our Renovation Issue in July.

Strawberry bud weevil or “clipper”:  All fields scouted this week were well beyond the bud stage, when clipper poses a threat.  Keep in mind that these insects could still pose a threat to raspberries or blackberries that are still in the bud stage.

Tarnished plant bugs continue to be absent in most fields scouted this week.  However, we have seen a few nymphs in more northern and coastal fields where plant development is behind fields in the south.  Therefore, fields that still have some plants in bloom or are just at petal fall should continue to be scouted for tarnished plant bugs nymphs, and controls should be applied if they exceed the threshold of 4 or more flower/fruit clusters infested with nymphs out of 30 clusters sampled.  Observe days-to-harvest restrictions on any insecticide used for tarnished plant bugs if you are nearing harvest on early varieties in the same field.

Large Tarnished Plant Bug Nymph

 

Two-spotted spider mites:  The on again, off again cool wet weather appears to have kept spider mite populations very low in strawberry fields this spring.  Nearly all fields scouted were free of mites, meaning that they will be very unlikely to require spider mite management prior to the end of harvest season.

Diseases:  Fields still in the bloom to late bloom stage may still need a fungicide spray to protect the blossoms from infection by spores, especially if they have been through recent rains.  Some varieties tend to be more susceptible to gray mold, and may need some special attention, given the amount of moisture we have had; for example Cabot, Cavendish and, anecdotally, Wendy.  If you start seeing symptoms on ripening fruit, you can use a fungicide to prevent secondary infections, such as Elevate® or Switch®, which are very good against Botrytis and have no days to harvest restrictions.  Oxidate® would be a similar option for organic growers.

Gray Mold on Strawberries

Gray Mold on Strawberries, photo by James Dill

 

Anthracnose fruit rot:  Remain vigilant for this fruit rot. Anthracnose is favored by warm, wet conditions, and this could occur, given the recent rains. Anthracnose appears as black sunken lesions on the sides of the fruit, and can appear suddenly and widespread in a field.  Fungicides including Cabrio® and Abound® can provide control of this fruit rot.

Anthracnose on Strawberry

 

Review:  Keeping Strawberries Fresh for Market
If you‘re bringing fruit to market, make sure that it arrives in the best condition possible.  Strawberries cool most efficiently if harvested early in the morning before they build up any field heat.  Place fruit into refrigerated storage quickly and keep it out of direct sunlight.  Fruit should be stored at 32° Fahrenheit and 95% relative humidity.  Cold air should be moved through the boxes or flats of fruit with a circulating fan and/or exhaust fan to cool most efficiently.  Temperatures lower than 32° may freeze the fruit and ruin its fresh quality.  A small, well-insulated building cooled with air conditioners and fans can provide effective temporary storage for strawberries.  If you don’t have refrigeration facilities, keep the fruit as cool as possible by harvesting when air temperatures are cool, and keeping it out of direct sunlight.  Transport the fruit to market as quickly as possible, and harvest only what you think you can sell in a day.

Annual Pre-Harvest Checklist for Pick-Your-Own
It’s that time again!  As harvest approaches, we like to remind you to take a moment and make sure that your farm is prepared to give your customers an enjoyable experience.  Take our annual review below to evaluate your customer readiness.

√      Signs to the farm are neat and easy to read.

√      There is easy access to the fields and plenty of parking.

√      Someone is ready to greet customers and offer parking instructions and directions to the field.

√      Access to the field is free of hazards.

√      Transportation is provided for the elderly and disabled.

√      The rules regarding picking are clearly posted.

√      Someone is in the field to show customers where to pick and to answer questions.

√      There are plenty of picking containers available.

√      Clean restroom and hand washing facilities are available.

√      Someone is available to help customers carry fruit out of the field.

√      The checkouts are fast and efficient.

√      Beverages are available.

√      Shade and seats are available for customers wanting to rest.

√      The help are friendly and knowledgeable.

A friendly, clean, and organized atmosphere will leave a lasting impression on your customers, encouraging them to come back and to recommend your farm to their friends.

Strawberry Harvest

Strawberry Harvest, photo by David Handley

 

Hold the Date!
Highmoor Farm Field Day is on Thursday, July 21, 2011, from 8:30 a.m. to 3:30 p.m.  Registration fee is $15.00, including lunch, and no preregistration is required.  For more information, visit the website:  www.extension.umaine.edu/highmoor/  or call 207.933.2100.

Sincerely,

David T. Handley
Vegetable & Small Fruit Specialist

Highmoor Farm                                   Pest Management
P.O. Box 179                                      491 College Ave
Monmouth, ME  04259                       Orono, ME  04473
207.933.2100                                     1.800.287.0279

Maine Cooperative Extension, the Land Grant University of the state of Maine and the U.S. Department of Agriculture Cooperating.  Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment.  A Member of the University of Maine System.

Any person with a disability who needs accommodations for this program should contact Pam St. Peter at 207.933.2100 to discuss their needs at least 7 days in advance.

Where brand names or company names are used it is for the reader’s information.  No endorsement is implied nor is any discrimination intended against other products with similar ingredients.  Always consult product labels for rates, application instructions and safety precautions. Users of these products assume all associated risks.

Strawberry IPM Newsletter No. 4 – June 10, 2011

Friday, June 10th, 2011

Strawberries

For full page print version, please see link at the bottom.

SOUTHERN STRAWBERRY GROWERS PICKING A FEW FRUIT

Pest Situation Mostly Calm, Watch for Sap Beetles, Birds

Situation:  A few berries are starting to be picked this week and an early field that was under row cover may open for harvest this weekend.  It appears that the season will open on about its normal date, although anxious customers have been calling and hoping to get into fields early.  We are still scouting for tarnished plant bug and spider mites in late blooming fields, although pest levels have remained mostly quite low this week.  As we move into the harvest season, its time to keep an eye out for other pests, including slugs, sap beetles and birds, which are as eager to enjoy the ripening fruit as your paying customers.

Strawberry bud weevil or “clipper”:  Most fields in southern Maine are well beyond the stage when clipper could pose a significant threat.  However, if you have very late blooming varieties or you are far enough north that many of the plants still have unopened buds, you should continue to scout for clipper damage.  One field was over threshold this week but the damage was occurring on small, tertiary and quaternary buds, with the primary and secondary already opened and undamaged, so the payoff of applying a spray was questionable.

Reminder to Raspberry Growers:  Strawberry clipper will move onto raspberry buds after strawberry bloom.  Check raspberry flower clusters for clipped buds and live clippers.  Insecticide sprays to control raspberry fruit worm adults, which are also active at this time, should provide some control of clipper as well.  Products registered for clipper on raspberries include Brigade®, Sevin XLR Plus® and Aza-Direct®.

Tarnished plant bugs were again few and far between in fields this week.  We have seen a few nymphs in southern Maine fields, but not enough to exceed the control threshold.  Fields still in bloom should continue to be scouted for tarnished plant bugs nymphs until petal fall.  Remember that this insect can also be a significant problem on day-neutral strawberry varieties, which flower and fruit in the late summer and fall.  This is when the insect is at its peak population, so feeding pressure on the crop can be intense.  Pay close attention to days to harvest restrictions on any insecticide used for tarnished plant bugs on day-neutral varieties, because often you will have to protect flowers at the same time as the fruit is ripening.

Large Tarnished Plant Bug Nymph

Third Instar Tarnished Plant Bug Nymph, photo by David Handley

 

Tarnished Plant Bug Injury

 

Two-spotted spider mites:  Strawberry fields continue to be relatively free of spider mites this spring.  Only two fields scouted this week showed the presence of mites, and only one of those was above the threshold of 25% of leaves infested.  Should we get a warmer, dryer stretch of weather mite populations could bounce up, so it is important to keep scouting right up until harvest.

Two-spotted Spider Mites

Two-spotted Spider Mites, photo by David Handley

 

Sap beetles are sometimes a problem as we start harvesting berries.  The 1/8 inch long, dark brown beetles chew small holes in ripening fruit, similar to slug injury.  They may be seen in the holes they’ve chewed into ripe fruit, but often drop to the ground when disturbed.  The best management strategy for sap beetles is good sanitation.  Keep the field free of overripe fruit by picking often and thoroughly. Insecticide sprays for this pest can be effective, but should be a last resort during the harvest period. Brigade®, Assail®, Dibrom® and PyGanic® are registered for control of sap beetles with pre-harvest intervals ranging from 12 to 24 hours.  Read the product label carefully for this and other application instructions and restrictions.

Sap Beetle

Sap Beetle, photo by New York State Agricultural Experiment Station

 

Diseases:  Fields with ripening fruit should have received the needed two to three bloom sprays for protection against gray mold by now.  Fields still in the bloom to late bloom stage may need a final spray to protect the blossoms from infection by spores, especially if they have been through some of the recent rain shower activity.

Gray Mold on Strawberries

Gray Mold on Strawberries, photo by James Dill

 

Powdery mildew:  This appears to be the most prevalent disease in strawberry fields this year.  Leaf cupping, reddening of leaf stems and fruit stems, and white, powdery fungal growth on the undersides of leaves has been seen to some degree in nearly every field.  Good growing conditions for the fungus have made it challenging to keep in check.  If you still have a bloom fungicide spray that should be applied, consider using a material that will also help control powdery mildew, such as captan, Topsin-M® or Pristine®.

Leaf spot infections are becoming more common in strawberry fields this week.  The spots usually appear on older leaves first, as small purple or red spots with white centers.  Leaf scorch has also been noted in a couple of fields (‘Darselect’ is quite susceptible to this).  The spots are smaller in the case of scorch, and lack the white centers.  Spots may coalesce to turn the leaves purple and necrotic, leading to the death of the leaf and weakening of the plant.  Many strawberry varieties have at least partial resistance to leaf spot and leaf scorch. Fungicides registered for leaf spots include captan, Topsin-M®, Syllit®, Cabrio®, Nova® and Pristine®.

Leaf Spot

Leaf Spot, photo by David Handley

 

Anthracnose fruit rot:  As fruit starts to ripen in fields that are wet from recent rain, be on the lookout for this fruit rot. Anthracnose is favored by warm, humid conditions and can spread rapidly under rainy, wet conditions, especially if puddles remain in a field after the rain.  Anthracnose appears as black sunken lesions with wet, orange (and sometimes gray) spore masses in them. The fungus is able to multiply on leaves without visible symptoms, which is why it may appear suddenly and widespread in a field.  Fungicides such as Cabrio® and Abound® can provide good control of anthracnose fruit rot.

Anthracnose on Strawberry

 

Birds, specifically cedar waxwings will be moving into fields to start feeding on ripe fruit, if they haven’t already.  These birds can destroy many of the early ripening fruit, despite our best efforts to scare them off.  Only by keeping a near constant presence in the field and eliminating roosting sites can you reduce the damage.  Usually, they are discouraged once the fields start to be regularly harvested and customers are present.  Songbirds are protected by law and should not be killed. However, permits may be issued for killing birds by the U.S. Fish and Wildlife Service if they receive a recommendation for such a permit from the Maine Wildlife Services Office (part of the USDA Animal and Plant Health Inspection Service) in Augusta, along with an application from the grower.  There is a $50 fee for the application, and it may take over a month for the permit to be processed.  However, the permit is good for one year, so if you have problems this season, you may consider applying for a permit this winter, which would allow you an option to kill birds, if necessary, next season.  The Wildlife Damage Office has recommendations for managing birds in crops, and also has some control options available through their office.  For more information on permits or bird control contact the office in Augusta at 207.629.5181.  The office is located in the Capital West Business Center at 79 Leighton Road in Augusta.

Cedar Waxwing

Cedar Waxwing, photo by Cornell University

 

Bird Damage on Strawberry

Bird Damage on Strawberry, photo by David Handley

 

Hold the Date!
Highmoor Farm Field Day, Thursday, July 21, 2011.

Sincerely,

David T. Handley
Vegetable & Small Fruit Specialist

Highmoor Farm                                    Pest Management
P.O. Box 179                                         491 College Ave
Monmouth, ME  04259                       Orono, ME  04473
207.933.2100                                       1.800.287.0279

Maine Cooperative Extension, the Land Grant University of the state of Maine and the U.S. Department of Agriculture Cooperating.  Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment.  A Member of the University of Maine System.

Any person with a disability who needs accommodations for this program should contact Pam St. Peter at 207.933.2100 to discuss their needs at least 7 days in advance.

Where brand names or company names are used it is for the reader’s information.  No endorsement is implied nor is any discrimination intended against other products with similar ingredients.  Always consult product labels for rates, application instructions and safety precautions. Users of these products assume all associated risks.

Strawberry IPM Newsletter No. 3 – June 3, 2011

Friday, June 3rd, 2011

Strawberries

For full page print version, please see link at the bottom.

CLIPPER IS ACTIVE ON LATE-BLOOMING VARIETIES

Powdery Mildew Infecting Many Fields

Situation:  Early varieties and plants that were under row covers in southern Maine are now just past bloom, with primary flowers starting to size into green fruit.  Later varieties are mostly in bloom this week.  The mix of hot and cold weather recently has made it challenging to predict when the crop will be ready, but it still looks as though it may only be a day or two behind a “normal” season.  Insect activity in strawberry fields has increased in the past week, most notably strawberry bud weevil or clipper.  Powdery mildew continues to be an issue in many fields, and cool weather may encourage the development of bacterial angular leaf spot.

Strawberry bud weevil or “clipper”:  Although we have seen increased clipper activity in most of the fields scouted this week, many fields in southern Maine are beyond the growth stage (blossoms in bud stage) where clipper poses a threat.  Once beds are in full bloom, clipper will not be able to cause economic harm.  However, fields not yet in full bloom should continue to be scouted.  Three fields were over the control threshold of 1.3 or more buds clipped per 2 foot of row length this week.

Clipper Beetle on Strawberry Blossom

 

Clipper Damage

Tarnished plant bugs continue to be relatively scarce in the fields scouted this week.  While we still have not found nymphs in most of the fields scouted, we did find them in some fields, and one field was over the threshold of 4 or more infested flower clusters per 30 sampled.  Warmer weather will likely bring about an increase in tarnished plant bug activity in the coming days, and strawberry flowers can remain susceptible to feeding injury even after petal fall.  Products registered for controlling tarnished plant bug include Brigade®, Danitol®, Malathion®, Thionex® and PyGanic®.  Bees and other pollinators are also active in your fields now, so apply pesticides at night when they are less active and use materials that pose the least threat to pollinators.  See page 115 of the 2010-2011 New England Small Fruit Pest Management Guide for more information (http://www.umass.edu/fruitadvisor/pdf/2010NESmallFruitGuide.pdf).

First Instar Tarnished Plant Bug Nymph

First Instar Tarnished Plant Bug Nymph, Photo by David Handley

Two-spotted spider mites:  In spite of a few warm days, the mostly cool, damp conditions appear to be keeping spider mites in check.  Most fields had no mites in our samples and those that had mites were well below the spray threshold of 25% of leaves infested.  Warmer weather will stimulate mite activity, so it is important to keep scouting in the coming weeks.

Spittlebugs:  We have been finding spittlebug masses in some strawberry beds this week.  The frothy spittle masses are found on the leaf stems (petioles), just below the leaflets, usually showing up around bloom.  Although spittlebugs don’t pose a significant threat to the plants, the frothy spittle masses create an annoyance for pickers.  Spittlebugs overwinter as eggs and the nymphs emerge in late May.  Start scouting for spittlebugs when the plants are at about 10% bloom.  Randomly inspect five one-square foot areas per field every week.  On hot, dry days the spittle masses may be at the base of the plants, so spread the leaves and inspect the crowns, leaf bases, leaf stems, and flower stems looking for the frothy spittle masses.  The small, yellow-orange nymphs will be under the spittle.  If the average number of spittle masses is more than two per square foot, a treatment may be warranted. Spittlebugs tend to be a greater problem in weedy fields. Pesticides currently registered for spittlebug control include Provado®, Thionex®, Danitol® and Brigade®.

Spittlebug

Spittlebug, Photo by David Handley

Slugs may be a problem in some fields this season.  Moist conditions encourage the presence of these mollusks. Slugs usually feed at night, leaving large holes and tunnels in ripening fruit.  Baits such as Deadline®  and Sluggo® offer some control of slugs, but should be used prior to fruit ripening.  Pay close attention to label instructions and precautions.  Baits should also be applied to the fields in mid-September if slugs have been a problem, to reduce egg-laying.

Slug on Strawberry

Slug on Strawberry, photo by James Dill

Diseases:  Most early fields are at the stage for a second application of fungicide to protect against gray mold.  Later blooming fields may now be ready for their first application.  Two to three sprays are generally required to provide good protection against Botrytis.  However, if rainfall exceeds more than one inch between sprays and wet conditions are prevalent, additional sprays may be required.

Powdery mildew:  We continue to find powdery mildew symptoms in nearly all fields scouted this week.  Conditions have apparently been just wet and warm enough to encourage its development in susceptible varieties.  Leaf cupping, purple leaf and flower stem lesions are being seen on many plants.  Mildew infections weaken plants and can reduce yield the following year.  Some varieties are more susceptible than others, for example Annapolis and Sable are quite susceptible, while Jewel, Mira and Mesabe are thought to be resistant.  Captan, Topsin-M®, Pristine®, Cabrio®, Quintec®, Procure® and Rally® are presently registered to control powdery mildew.

Powdery Mildew

Powdery Mildew, photo by David Handley

Bacterial angular leaf spot:  We have not yet found plants with symptoms of angular leaf spot (Xanthomonas fragariae) this spring, but the cool wet conditions may encourage this disease if it is present in your field.  Angular leaf spot is a bacterial disease characterized by small, translucent or “water-soaked” leaf spots that occur between the veins.  The spots coalesce, turn yellow, reddish and eventually black.  The symptoms start on the lower leaves and move up as bacterial spores are splashed by rain or irrigation water.  Infection of the calyxes may also occur, resulting in blackened berry stems and caps.  Irrigation for frost protection can encourage the development of this disease, although watering has not been needed yet for frost this spring.  Copper-containing chemicals, such as Kocide®, Cuprofix®, and Bordeaux are the only materials that have some effect on this disease. Some labels suggest adding lime as a “safener” to reduce the risk of crop injury.  Spray applications need to begin before bloom to prevent spread of bacteria on the leaves before they spread to berry caps.  Application of copper sprays after bloom can result in fruit injury and is not recommended.  Therefore, most fields are now past the stage where copper should be considered.  Recent research suggests that hydrogen dioxide (OxiDate®) may also have some activity against angular leaf spot when used on strawberries as part of a gray mold management program.

Angular Leaf Spot

Bacterial Angular Leaf Spot, Photo by David Handley

Don’t Forget: Twilight Meeting in Lewiston on June 8
The University of Maine Cooperative Extension and the Maine Vegetable and Small Fruit Growers Association are sponsoring a growers meeting at R. Belanger & Sons Farm in Lewiston on Wednesday, June 8th at 5:30 p.m.  Come tour the new packing and storing facility, get a look at look at early vegetables and discuss the strawberry season ahead.  One pesticide applicator re-certification credit will be available.  Belanger and Sons Farm is located at 262 Cotton Road in Lewiston.  Directions:

From the north:  On the Maine Turnpike I-95, take Exit 80 toward Rt. 196/Lewiston.  Merge right onto Alfred Plourde Pkwy.  Take ramp onto Rt. 196, E. Lisbon St., then slight right onto Pleasant St., then slight left onto Commercial St.  Travel 2 miles on Ferry Rd.  Turn left onto Cotton Rd.  The farm is on the left.

From the south:  On the Maine Turnpike I-95, take Exit 80 toward Rt. 196/Lewiston.  Turn right onto Alfred Plourde Pkwy.  Turn left onto River Rd. and travel 2 miles.  Continue onto Ferry Rd., then turn right onto Cotton Rd.  The farm is on the left.

Sincerely,

David T. Handley
Vegetable & Small Fruit Specialist

Highmoor Farm                                   Pest Management
P.O. Box 179                                      491 College Ave
Monmouth, ME  04259                        Orono, ME  04473
207.933.2100                                     1.800.287.0279

Maine Cooperative Extension, the Land Grant University of the state of Maine and the U.S. Department of Agriculture Cooperating.  Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment.  A Member of the University of Maine System.

Where brand names or company names are used it is for the reader’s information.  No endorsement is implied nor is any discrimination intended against other products with similar ingredients.  Always consult product labels for rates, application instructions and safety precautions. Users of these products assume all associated risks.

Any person with a disability who needs accommodations for this program should contact Pam St. Peter at 207.933.2100 to discuss their needs at least 7 days in advance.

Strawberry IPM Newsletter No. 2 – May 27, 2011

Friday, May 27th, 2011

 

Strawberries

For full page print version, please see link at the bottom.

WARMER WEATHER BRINGS BLOOMS!

Insect & Mite Pest Pressure Very Low, Time to Protect for Gray Mold

Situation:  Strawberry plants that spent the early spring under row covers are now at full bloom in southern Maine, and early varieties that were not covered are in early bloom.  Although some late varieties are still in the bud stage, it appears that we will be looking at a near normal ripening season unless temperatures become abnormally cool over the next few weeks.  Southern fields are looking to open around the 17th to 20th of June.  We continue to be fortunate in terms of frost, but recent thunder showers have caused concern about the potential for hail.   Hopefully the few days of clear weather we have experienced recently will help with pollination, as bee activity has been hampered by the prolonged cool temperatures and rain.

Strawberry bud weevil or “clipper”:  Although there are flower buds aplenty around the state this week, we have seen remarkably little indication of clipper activity.  We have seen just a few live clippers and several clipped buds; but none of the fields we scouted were over the spray threshold of more than one clipped bud per two feet of row length.   Therefore early blooming fields may not require any spray for clipper this spring, as they won’t cause damage after bloom.  However, later blooming varieties may begin to show more damage in the coming days and should continue to be scouted for clipped buds.

Clipper Beetle on Strawberry Bud

Clipper Beetle on Strawberry Bud, Photo by James Dill

 

Clipper Injury

Clipper Injury, Photo by David Handley

Tarnished plant bugs were also scarce in the fields scouted this week.  Although we did see numerous adults in some fields we have still not found any immature stage bugs, or nymphs, infesting strawberry flower clusters.  While the cool, wet conditions may have delayed the emergence of the nymphs, the presence of the adults suggests that they may soon become a concern.  The nymphs are small, active, yellow-green insects, and it is important to scout for them often, as they can show up quickly in warm weather.  For control options, review last weeks issue of this letter or see the 2010-2011 New England Small Fruit Pest Management Guide (http://www.umass.edu/fruitadvisor/pdf/2010NESmallFruitGuide.pdf).

First Instar Tarnished Plant Bug Nymph

First Instar Tarnished Plant Bug Nymph, Photo by David Handley

 

Tarnished Plant Bug Adult

 

Tarnished Plant Bug Injury on Strawberries

Two-spotted spider mites have only been found in a few fields this week, mostly on plants that were under row covers.  However, none of the fields scouted were over the threshold of 25% or more of leaves infested.  Mites tend to exhibit little growth under cool, wet conditions, so our recent weather has probably kept them in check.  It is likely that overwintering adults are now laying eggs and that we will start seeing more mites once we get a stretch of warm, dry weather.

Cyclamen mites:  We have seen some plants showing the crinkled leaves characteristic of cyclamen mite damage, but have only found live mites in one field, which was also infested last year.  We will continue to keep a lookout for this pest as it may become more prevalent once the temperatures start to rise.

Cyclamen Mite Damage

Cyclamen Mite Damage, photo by David Handley

Root weevil management
We have found strawberry root weevils in three fields this spring, so apparently they came through the winter very well.  The infested plants appear weak and stunted, and often wilt on hot days.  Digging under the plants reveals the small (1/4 -1/2”) crescent-shaped grubs.  The grubs usually begin to pupate when the plants are in bloom, but this week we found just small and large grubs and no pupae.  Control of this pest is difficult. It is too late to apply the registered insecticide (Platinum®) for the grubs in fruiting fields, as it requires a 50 day pre-harvest interval.  If you intend to keep an infested field for another year, you can apply Brigade® insecticide for the adult weevils once they have emerged and begin feeding on the foliage, usually in mid-July just before renovation.  In order to maximize effectiveness it is recommended that you use the full labeled rate and apply the material at night when the weevils are most active.

Strawberry Root Weevil Grub

Strawberry Root Weevil Grub, photo by David Handley

Diseases:  Many fields have received an early bloom stage fungicide spray to protect them from spores of Botrytis cinerea, the fungus that causes gray mold.   Two to three sprays of fungicide during bloom are typically required to provide good protection against this disease.  Generally an early bloom (5-10%) spray, a full bloom spray and a third cover at late bloom to petal fall will provide good control of this disease.  However, if rainfall exceeds more than one inch between sprays and wet conditions are prevalent, additional sprays may be required.  Alternatively, if conditions remain very dry after the second spray, then a third spray may not be necessary.

Leather rot (Phytopthora cactorum) continues to be a threat if you have had very wet conditions during bloom, especially if there has been standing water in the field.  Foliar sprays of Aliette®, Agri-Phos® or Phostrol® (similar to Aliette®) may also provide control.  Sprays should be applied during bloom and fruit development.

Red stele root rot:  We have seen mild symptoms of red stele in two fields this spring.  Given the wet, cool soil conditions this spring, infections were likely.  However, symptoms appeared very late and should conditions become warm and dry, there shouldn’t be much further spread this year.  If infested fields are going to be carried over, an application of Ridomil Gold®, Alliette® or Phostrol® should be applied in the fall.  Foliar sprays of Alliette® or Phostrol® can still be applied this spring.

Powdery mildew:  This fungus disease has been observed in nearly all fields this week, although symptoms thus far have been mild.  Leaf cupping and pinkish purple leaf and flower stem lesion symptoms could be seen on susceptible varieties.  When planning protective bloom sprays for gray mold, consider using a fungicide that will also control powdery mildew, such as captan + Topsin-M®, or Pristine®.

Powdery Mildew

Powdery Mildew, photo by David Handley

Vegetable & Berry Growers Twilight Meeting on June 8, 2011
The University of Maine Cooperative Extension and the Maine Vegetable and Small Fruit Growers Association will hold a growers meeting at R. Belanger & Sons Farm in Lewiston on Wednesday, June 8th at 5:30 p.m.  We will tour Rick Belanger’s new packing and storing facility designed to meet new GAP certification standards, look at some early vegetables and look over the strawberry plantings while discussing pest management strategies for the season ahead.  One pesticide applicator re-certification credit will be available for attending the meeting.  Please join us!  Belanger and Sons Farm is located at 262 Cotton Road in Lewiston.  Directions:

From the north:  On the Maine Turnpike I-95, take Exit 80 toward Rt. 196/Lewiston.  Merge right onto Alfred Plourde Pkwy.  Take ramp onto Rt. 196, E. Lisbon St., then slight right onto Pleasant St., then slight left onto Commercial St.  Travel 2 miles on Ferry Rd.  Turn left onto Cotton Rd.  The farm is on the left.

From the south:  On the Maine Turnpike I-95, take Exit 80 toward Rt. 196/Lewiston.  Turn right onto Alfred Plourde Pkwy.  Turn left onto River Rd. and travel 2 miles.  Continue onto Ferry Rd., then turn right onto Cotton Rd.  The farm is on the left.

Sincerely,

David T. Handley
Vegetable & Small Fruit Specialist

Highmoor Farm                                   Pest Management
P.O. Box 179                                      491 College Ave
Monmouth, ME  04259                       Orono, ME  04473
207.933.2100                                  1.800.287.0279

Maine Cooperative Extension, the Land Grant University of the state of Maine and the U.S. Department of Agriculture Cooperating.  Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment.  A Member of the University of Maine System.

Any person with a disability who needs accommodations for this program should contact Pam St. Peter at 207.933.2100 to discuss their needs at least 7 days in advance.

Where brand names or company names are used it is for the reader’s information.  No endorsement is implied nor is any discrimination intended against other products with similar ingredients.  Always consult product labels for rates, application instructions and safety precautions. Users of these products assume all associated risks.

Strawberry IPM Newsletter No. 1 – May 19, 2011

Thursday, May 19th, 2011

Strawberries

For full page print version, please see link at the bottom.

2011 STRAWBERRY PEST MANAGEMENT SEASON BEGINS

Cool Damp Weather Slows Bloom; Pests?

Extended cool, damp weather has slowed strawberry development over the past week, making bloom seem late, especially compared to last season’s very early start.  Looking for the silver lining in this stretch of bad weather, we can speculate that it should keep spider mites and tarnished plant bugs in check, at least temporarily, as past experience has shown us these pests tend to have less success reproducing under cool, wet conditions.  However, gray mold, caused by the fungus Botrytis, can develop quite well under these conditions, and growers should be ready to get a protective fungicide on their plants as soon as bloom begins.  We will start scouting strawberry fields for major insect pests in earnest next week, including volunteer farms in North Berwick, Wells, Cape Elizabeth, Poland Spring, New Gloucester, Dresden, Monmouth, Wayne, and Farmington, and will be reporting our findings through this newsletter on a weekly basis until harvest time.  You can also get quick access to this information through our blog at http://extension.umaine.edu/highmoor/ or the Pest Management web page at http://umaine.edu/ipm/programs/.  If you would like to receive this newsletter via email, please give us a call at 207.933.2100 or send an email message to:  pamela.stpeter@maine.edu.

The best way to manage strawberry pests is to scout your own fields regularly and often.  Start now, if you haven’t already.  You should be able to identify the major pests and their damage, and be able to determine if control measures are necessary.  To properly scout your fields you may want a copy of the Strawberry Production Guide for the Northeast, Midwest and Eastern Canada.  This contains detailed information on strawberry pest identification and monitoring, and also provides information on all other aspects of strawberry production.  It may be purchased for $45.00 per copy from the University of Maine Cooperative Extension.  You can order it online at: http://extensionpubs.umext.maine.edu/.  You should also have a copy of the 2010-2011 New England Small Fruit Pest Management Guide, which contains the latest information on management control options for the major strawberry pests as well as scouting information.  Color pictures of the important strawberry pests are now also printed in the 2010-2011 New England Vegetable Management Guide.  Call or e-mail us if you are interested in purchasing copies of these guides.

Situation:  Early varieties and plants that were under row covers are now showing a few king blossoms in southern and mid-state fields, but development will continue to be slow until temperatures finally start to rise.  So far, there have been no reports of significant winter injury, as we had few days of severe cold and good snow cover for most of the winter.  I have seen a little bit of frost injury on some very early flowers that were under row covers, but so far it has not been a difficult season for frost.  There is certainly the threat of frost injury for at least another two weeks, so pay close attention to weather reports and be ready to protect the buds and blossoms should the temperature dip below freezing.  Bear in mind that if fields need to be irrigated for frost repeatedly in the coming weeks we will increase the risk of bacterial angular leaf spot becoming a problem.

Angular Leaf Spot

Bacterial Angular Leaf Spot, Photo by David Handley

Strawberry bud weevil or “clipper” should start becoming active in strawberry fields as more flower buds emerge.  I haven’t found signs of adult feeding activity (holes in flower petals) yet, as the wet weather has probably slowed them down, but expect clippers to be active in the coming days as more flower buds become available.  The clipper is a small weevil, which girdles strawberry flower buds, causing them to dry up and fall off the flower stalk.  Scout for damage by counting the number of clipped buds in two feet of row length at five different locations in a field.  If the average number of clipped buds per two-foot sample exceeds 1.2, or if live clippers are found, control measures are recommended.  Damage is usually first noticed at the edges of the field.  Border sprays may be effective in keeping this insect from becoming a problem in larger fields.  Fields with a history of clipper problems will typically exceed threshold nearly every year.  Insecticide options for clipper include Lorsban®, Brigade®, Sevin® and PyGanic®.

Clipper Feeding On Petals

Feeding Signs of Strawberry Clipper, photo by David Handley

 

Clipper Damage

Tarnished plant bugs have not yet been observed in the field, but these are hard to find on wet plants.  The damp weather may reduce their egg-laying success, however, so let’s hope we’ll not see too much pressure on the flowers as the weeks progress.  Once the eggs do start to hatch, we’ll start seeing the immature bugs, or nymphs, feeding in the flowers.  The nymphs are small, active, yellow-green insects.  It is important to scout for the nymphs regularly, as they can show up quickly in warm weather.  Tarnished plant bugs feed on the open strawberry flowers, causing the berries to have seedy ends.  To scout for this insect shake 30 flower clusters (six clusters in five different locations) over a plate.  If four or more of the clusters out of the 30 sampled have any nymphs, control measures should be taken.  Be on the alert and scout your fields now! Insecticide options for tarnished plant bug include malathion, Brigade®, Danitol®, Thionex® and PyGanic®.

Tarnished Plant Bug Adult

Tarnished Plant Bug Adult, photo by David Handley

Cyclamen mites:  Plants showing weak growth and yellow, pinkish or blackened, crinkled leaves may be infested with cyclamen mite.  Cyclamen mites are very small, smaller than spider mites, and reside in the crown of the strawberry plant feeding on the developing leaves and flower buds.  They are very hard to see, even with magnification.  Infested plants have shrunken distorted leaves and flower stalks, and produce few, if any, marketable fruit.  Miticides such as Thionex® or Kelthane® and Temprano® can be effective, but must be applied in lots of water to be sure that the material is carried down into the crowns where these mites reside. I already have found cyclamen mites in one field this week, and many fields were infested last year, so be on the look out for these symptoms.

Cyclamen Mite

Cyclamen Mite Damage on Strawberry Plant, photo by David Handley

Two-spotted spider mites have not yet been a problem this spring, but growers with plants under row covers should be alert.  This is often where we first find mite problems.  Spider mites will reproduce rapidly when warmer weather arrives, so it is important to scout for them regularly.  Spider mites feed on the undersides of strawberry leaves, rasping the plant tissue and sucking the sap.  Infested leaves will develop yellow flecking and a bronzed appearance.  The plants become weakened and stunted.  Fields that have had excessive nitrogen fertilizer and/or row covers tend to be most susceptible to mite injury.  To scout for mites, collect 60 leaves from various locations in the field, and examine the undersides for the presence of mites.  Mites are very small – you may need a hand lens to see them.  Chemical control options for two-spotted spider mites include Acramite®, Savey®, Zeal®, Vendex®, Oberon®, Brigade®, Danitol®, Thionex® and JMS Stylet oil® (oils will cause plant injury if used in combination with captan or within 14 days of an application of sulfur).

Root weevil management
Given the relative mild winter we should expect to see good survival of strawberry root weevil and black vine weevil in fields that were previously infested.  Infested plants appear week and stunted, usually in somewhat circular patches in a field.  Digging under the plants will reveal small (1/4 -1/2”) crescent-shaped legless grubs.  Typically, the grubs begin to pupate when the plants are in bloom, but we have seen both small grubs and pupae already this spring.  A soil drench of Platinum® (thiamethoxam) insecticide during the spring and/or fall when the grubs are active in the soil can provide control.  However, Platinum® has a 50 day pre-harvest interval, so it is too late for applications in most fruiting fields this year.  Platinum® may also be used as a pre-plant or planting treatment for root weevils.

Diseases:  Bloom is a critical time to protect strawberry fruit against gray mold caused by the fungus Botrytis cinerea, especially when conditions have been damp.  Two to three sprays of fungicide during bloom are typically required to provide good protection against this disease.  If you tank mix insecticides and fungicides, avoid spraying when bees are active.  Botrytis cinerea overwinters on old leaves and plant debris.  Fruit infections take place almost exclusively through the flowers, so gray mold control efforts must be focused on the bloom period.  If the bloom period is dry and/or good fungicide coverage is maintained, incidence of gray mold at harvest should be low.

There are several excellent fungicide choices for control of gray mold in strawberries.  Elevate® (fenhexamid) has good to excellent activity against Botrytis.  Captevate® is a pre-mix of captan and fenhexamid and has a broader spectrum of activity than Elevate® alone.  Switch® (cyprodinil and fludioxonil), Scala® (pyramethanil) and Pristine® (pyraclostrobin and boscalid) are also excellent products for gray mold control.  Topsin M® + captan is also a good fungicide combination, but remember that captan is strictly a protectant and can be washed off by rain or irrigation water.  Thiram is similarly effective but also susceptible to wash-off.

The fungicides Cabrio® (pyraclostrobin) and Abound® (azoxystrobin) are NOT suitable for gray mold control, but are effective against anthracnose and other fruit rot and leaf spot diseases.  All fungicides mentioned above have a 0-day pre-harvest interval, except Topsin M® (1 day) and thiram (3 days).  Remember to alternate fungicides with different modes of action for resistance management purposes.

Leather rot (Phytopthora cactorum) may also become an issue when you have a lot of water in the fields during bloom and fruit development, especially if you did not get mulch on the fields last fall and the plants are on bare, wet soil.  Leather rot is best controlled by growing strawberries in well-drained soil and applying straw mulch between the rows to prevent berries from touching the soil and reduce any soil from splashing up onto the berries.  Foliar sprays of Aliette®, Agri-Phos® or Phostrol® (similar to Aliette®) may also provide control.  Sprays should be applied during bloom and fruit development.

Red stele root rot
Although fall and early spring conditions were not especially conducive to red stele development, damp conditions this spring should make us alert for this root rot if any fields appear to be weak, stunted or dying.  To diagnose red stele, pull up a few plants that look weak and scrape the roots of these plants to see if the center of the root, known as the stele, is a rusty red in color, instead of the normal white.  The red color would indicate an infection. Red stele is caused by Phytophthora fragariae, a soil pathogen that infects roots when soils are wet with temperatures are around 50°F.  The pathogen grows into the roots causing the plants to become weak, stunted and eventually die.  Symptoms are most evident in the spring, and can be mistaken for winter injury. Ridomil Gold®, Alliette® or Phostrol® are fungicides that can be applied in the late fall or early spring for control of red stele.  Many varieties have some level of resistance to the disease, but the most effective management strategy is to plant only into well-drained soils, and/or plant onto raised beds.

Powdery mildew:  This fungus disease has been starting to show up as purple or red blotches on the leaf petioles and flower stems in some fields.  Most of us are more familiar with the later symptoms of upward curling of the leaves and white, powdery growth on the undersides of the leaves.  Check your fields for pinkish purple leaf and flower stem lesion symptoms now.  Abound®, captan, Pristine®, Cabrio®, Topsin-M® and JMS Stylet oil® are presently registered to control powdery mildew.

Vegetable & Berry Growers Twilight Meeting on June 8, 2011
The University of Maine Cooperative Extension and the Maine Vegetable and Small Fruit Growers Association will hold a growers meeting at R. Belanger & Sons Farm in Lewiston on Wednesday, June 8th at 5:30 p.m.  We will tour Rick Belanger’s new packing and storing facility designed to meet new GAP certification standards, look at some early vegetables and look over the strawberry plantings while discussing pest management strategies for the season ahead.  One pesticide applicator re-certification credit will be available for attending the meeting. Please join us!  Belanger and Sons Farm is located at 262 Cotton Road in Lewiston.  We’ll provide more detailed directions in a future issue.

Sincerely,

David T. Handley
Vegetable & Small Fruit Specialist

Highmoor Farm                                   Pest Management
P.O. Box 179                                      491 College Ave
Monmouth, ME  04259                       Orono, ME  04473
207.933.2100                                     1.800.287.0279

Maine Cooperative Extension, the Land Grant University of the state of Maine and the U.S. Department of Agriculture Cooperating.  Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment.  A Member of the University of Maine System.

Where brand names or company names are used it is for the reader’s information.  No endorsement is implied nor is any discrimination intended against other products with similar ingredients.  Always consult product labels for rates, application instructions and safety precautions.  Users of these products assume all associated risks. 

Any person with a disability who needs accommodations for this program should contact Pam St. Peter at 207.933.2100 to discuss their needs at least 7 days in advance.

 

Strawberry IPM Newsletter No. 6 – June 28, 2010

Tuesday, June 29th, 2010

Strawberries

For full page print version, please see link at the bottom.

Renovation and Weed Management Issue

Early Harvest Offers Opportunity for Early Renovation

The night of May 10 quickly changed the outlook for the 2010 Maine strawberry crop.  A warm, dry spring led to a very early bloom and greatly increased the risk of frost injury to the flowers. On the night of May 10 temperatures in some fields dropped into the low 20’s, despite predictions of temperatures in the low to mid 30’s.  Growers who were alerted to the situation in time and could irrigate their fields suffered relatively little damage.  For growers who were not able to water, most of the primary and secondary blossoms were lost, leading to significant reductions in yield and a delay in ripening.  However, most growers who saw high levels of blossom damage in their fields still had a salable crop this season, although fruit size and total yield was reduced.

Strawberry Frost Injury

Frost Injury to Flowers and Leaves, Photo By David Handley

Insect pressure from both tarnished plant bug and strawberry clipper was relatively light this spring.  Cyclamen mites, and lately potato leafhopper have been an issue in some fields, causing plant stunting and poor growth.  Customers appear to have been alerted to the early harvest season, as pick your own fields were generally doing good business and pre-picked sales were very strong.

Bed renovation should begin as soon after harvest as possible, and our early season this year should allow us to start renovation a bit sooner than normal.  Early renovation allows more time for runner plant development, leading to larger crowns and more flower buds for next year.  Early renovation also improves weed management by tilling in many weeds before they go to seed, and can help with insect and foliar disease control by interfering with life cycles at a critical stage of development.

Strawberry Bed Renovation Review
The first step in the bed renovation process is to determine which beds should be carried over for another year and which should be plowed down and put into a crop rotation.  Beds that did not suffer much from winter injury, had good production and a good plant stand with no major weed, insect or disease problems should be carried over for another year.  Beds that do not meet these criteria should be plowed down and seeded to a suitable cover crop to reduce weed, insect and disease problems that have developed and to increase soil organic matter content.   Ideally, beds that are plowed down should be rotated out of strawberries for at least three years.  If properly managed, crop rotation will greatly reduce pest problems and improve the vigor and longevity of strawberry beds without the need for soil fumigation.

Renovating a strawberry bed is basically a thinning process to promote healthy new growth that can support a heavy crop next spring.  While some of the general renovation scheme may need to be modified for individual situations, all beds should undergo the following steps once harvest is complete.

1. Broadleaf weed control:  If perennial broadleaf weeds such as dandelion, shepherd’s purse, daisy or goldenrod are a problem and/or a high population of annual broadleaf weeds such as lambsquarters, sorrel or pigweed are present, hand-pull as many as possible, especially within the plant rows, and/or apply 2,4-D amine (Formula 40®).

2. Leaf mowing:  Four to five days following the 2,4-D application (or immediately if 2,4-D was not applied) mow off the leaves of the strawberries about 1½ inches above the crowns.  If the planting is weak, it is recommended that this step of the renovation process be skipped.

Mowing Strawberry Leaves

 

3. Fertilization:  Apply 40 to 60 pounds of actual nitrogen per acre (use the higher rate on sandy soils and fields where growth has been weak).  Phosphorus and potassium applications should be made according to soil test recommendations.  Soil testing kits and information are available from your county Cooperative Extension office.10-10-10

Strawberry Bed Renovation

 

5. Pre-emergent weed control:  To control annual weeds, apply terbacil (Sinbar® 80WP) according to label directions (2 to 6 oz. per acre).  Be sure to follow all label precautions. To avoid plant injury, do not use terbacil if you do not intend to mow off the leaves.  Napropamide (Devrinol®) or DCPA (Dacthal®) may be used as an alternative to terbacil at this time, as described below.  If you are not using herbicides, regular cultivation, before weeds are more than 2” tall, will be needed throughout the summer.

6. Subsoiling:  Soil compaction caused by tractor and picker traffic in the field can cause soil drainage problems and interfere with good root development.  Using a subsoiling blade between the rows will break up compacted layers of soil and improve water infiltration. Subsoiling is best done late in the renovation sequence to prevent interference from straw and crop residues.

7. Irrigation:  To encourage rapid plant growth and get the most out of fertilizers and herbicides, irrigate the beds regularly.  Strawberries will grow best if they receive 1½ inches of water per week during the growing season.

Strawberry Irrigation

Strawberry Irrigation, photo by David Handley

 

Don’t forget your plants once these renovation steps are completed.  Check the strawberry fields regularly during the summer for pest problems.  Finding and managing problems early can prevent major problems next spring. Pay close attention to the following items:

Nutrition:  Following the application of 40 to 60 pounds of actual nitrogen at renovation, another 20 pounds of nitrogen may be applied in mid- to late-August to stimulate flower bud development.

Sidedressed Strawberry Planting

Sidedressed Strawberry Planting, photo by David Handley

 

One way to determine the nutrient status of strawberry plants during the summer is to have a leaf tissue analysis done.  Tissue analysis offers a view of what is happening within the plant, and can spot any nutrient deficiencies.  In combination with regular soil tests, tissue analysis will provide a complete picture of a field’s fertilizer needs. For more information about tissue analysis contact: Analytical Lab, 5722 Deering Hall, Rm. 407, University of Maine, Orono, ME 04469-5722, telephone: 581.2945, Web page: http://anlab.umesci.maine.edu/ .

Diseases:  Foliar diseases should be monitored in your fields by regularly examining leaves.  We have seen all of the common leaf diseases in fields this spring and expect that they will continue to be a problem through the summer.  The most common summer diseases are powdery mildew, leaf spot and leaf scorch.  Fungicides available for these diseases include captan, Topsin-M®, Cabrio®, Pristine® and Abound®.  See the 2010-2011 New England Small Fruit Pest Management Guide for detailed descriptions of these diseases and their management.

Leaf Scorch

Leaf Scorch, photo by David Handley

 

Insects:  If black vine weevils or strawberry root weevils are a problem in a strawberry field that you would like to carry over, bifenthrin (Brigade®) can be applied when adult feeding is noticed (usually until mid-late July).  Look for notching along the leaf edges and the presence of the black or brown snout beetles.  Applications should be made at night when these insects are active, and the highest rate of the insecticide should be used.  For control of the grubs, a soil drench of Platinum® (thiamethoxam) insecticide should be applied during the fall and/or early spring when the grubs are active in the soil.  This product has a 50 day pre-harvest interval and may also be used as a pre-plant or planting treatment for root weevils.  Parasitic nematodes such as Heterorhabditis bacteriophora or Steinernema feltiae can also be applied to provide control of root weevil grubs in late August.  Nematodes require specialized handling and application. Contact us or talk with one of the suppliers for more details.  See the New England Small Fruit Pest Management Guide for sources.

Black Vine Weevil

Black Vine Weevil, photo by David Handley

 

Strawberry rootworm (not root weevil) is a small (1/8″) dark brown to black beetle, which feeds on strawberry foliage, causing it to look skeletonized.  The small larvae feed on strawberry roots, further weakening the plant.  Adult feeding damage on the leaves usually occurs in late July through August.  Heavy rootworm feeding weakens strawberry plants so control is warranted when injury is noticed.

Strawberry Rootworm Beetle

Strawberry Rootworm Beetle, photo by James Dill

 

Keep a lookout for potato leafhoppers, which can weaken strawberry plants and spread disease.  The potato leafhopper does not overwinter in Maine, but must fly in from southern states.  These small, bullet-shaped insects feed on plant sap from the undersides of leaves, causing the leaves to become curled, stunted and yellow-streaked.  Symptoms are often first noticed in new strawberry plantings, but leafhoppers will also infest older plantings and a variety of vegetables, flowers and fruit crops.  To scout for leafhoppers, brush the leaves of the plants with your hand.  The small, whitish adults can be seen flying off the plant.  Examine the underside of some injured leaves.  Look for small, light green leafhopper nymphs.  They are about 1/16 inch long.  When touched, they will crawl sideways in a crab-like manner.  Controls for potato leafhoppers include malathion, carbaryl or Provado®.

Potato Leafhopper

Potato Leafhopper, photo by New York State Agricultural Experiment Station

 

hopperburn1

Leafhopper Burn, photo by David Handley

 

Mites:  Two-spotted spider mites can become problems during the summer.  Continue to take leaf samples for spider mites after renovation.  If more than 25% of a 60-leaf sample has mites, controls should be applied.  Summer is an ideal time to use predatory mites to control pest mites, because they prefer warm temperatures, and there is less chance of an insecticide spray that might kill them.  Amblyseius fallacis, can provide good control of two-spotted spider mites when they are released at a rate of about 10,000 mites per acre.  Predator mite releases should only be made after a spider mite infestation has been found in the field.  Releasing predators into a clean field will often result in them dying, due to a lack of food.  See the New England Small Fruit Pest Management Guide for sources of predatory mites.

Two-spotted Spider Mites

Two-spotted Spider Mites, photo by David Handley

 

Cyclamen mites:  Plants showing weak growth and yellow, crinkled leaves may be infested with cyclamen mite.  Cyclamen mites are very small and reside down in the crown of the strawberry plant feeding on the developing leaves.  They are very hard to see, even with magnification.  Miticides such as Thionex® or Kelthane® can be effective, but must be applied in lots of water to be sure that the material is carried down into the crowns. If you suspect you have this problem, give us a call.

Cyclamen Mite Damage

Cyclamen Mite Damage, photo by David Handley

 

Weeds:  Weeds tend to become a big problem during the summer because they are often forgotten among all the other demands on our time and because of limited chemical control options.  However, the importance of good weed management should not be underestimated.  Keeping weeds under control this summer will prevent future infestations.  Here’s a summary of weed control options for strawberries:

  1. Cultivation:  Following renovation, cultivation between strawberry rows can provide effective temporary control of annual weeds.  Several types of cultivators are available which will work well in strawberry beds.  Cultivators can also be used to help sweep runners into the plant rows.
  2. DCPA (Dacthal®):  A pre-emergent herbicide used in the early spring, late fall or after renovation.  It offers good, short-term control of some annual broadleaf weeds and grasses.  It is weak on ragweed, galinsoga, smartweed, shepherd’s purse and mustard.  Its action will be improved if worked into the soil by irrigation or light cultivation, and it tends to work best in lighter, warmer soils.  This may be used as an alternative to terbacil or napropamide when there is a high risk of plant injury from those products.
  3. Napropamide (Devrinol®):  A pre-emergent herbicide which provides good control of annual grasses, volunteer grains and some broadleaf weeds.  It is typically applied just before mulching in the fall.  Split applications have become popular due to the loss of other pre-emergent herbicides, e.g. half maximum rate application after renovation or in late summer after desired daughter plants have rooted, and a second half rate application once the strawberry plants are dormant.  Napropamide should be activated by irrigation, rainfall or light cultivation within 24 hours of application.  Repeated long-term use of this material, i.e. with no crop rotation, may eventually result in poor daughter plant establishment, due to rooting inhibition.
  4. Terbacil (Sinbar®):  An effective pre-emergent herbicide with some post-emergent activity, which should be applied at renovation time – after mowing and tilling the beds, but before new growth begins.  A second application can be made in late fall, after the plants are dormant.  No more than 6 oz. may be applied in a single application, and no more than 8 oz. may be applied in one season.  An example of one season’s use could be 5 oz. applied at renovation and 3 oz. applied in the late fall, the latter in addition to napropamide or DCPA.  Terbacil can cause injury to strawberry plants.  It is important to determine appropriate rates for each location.
  5. Sethoxydim (Poast®):  A post-emergent herbicide for control of actively growing grasses.  It will not control broadleaf weeds.  It should not be applied when grasses are under stress, e.g. drought, or on unusually hot, humid days.  Do not use sethoxydim within six weeks of a terbacil (Sinbar®) application to avoid leaf injury.  Sethoxydim should be used in combination with a crop oil concentrate.  Do not tank mix with 2, 4-D.
  6. Clethodim (Arrow®, Prism®, Select®):  A post-emergent herbicide, similar in activity to Poast®, for control of actively growing grasses.  It will not control broadleaf weeds.  It should not be applied when grasses are under stress, e.g. drought, or on unusually hot, humid days.  Clethodim should be used in combination with a crop oil concentrate.
  7. Paraquat (Gramoxone Inteon®):  A contact herbicide for post-emergent control of most annual weeds and suppression of many perennial weeds.  Paraquat will injure or kill strawberries, so applications are made between rows only, with a sprayer shielded to protect the strawberries.  It should be used in combination with a nonionic surfactant.  Paraquat should not be applied within 21 days of harvest or more than three times in one season.
  8. Pelargonic acid (Scythe®):  A contact herbicide for post-emergent control of most annual weeds and suppression of many perennial weeds.  Scythe will injure or kill strawberries, so applications are made between rows only, with a sprayer shielded to protect the strawberries.  This product has a relatively low toxicity and no residual soil activity.  It has a strong, unpleasant odor.
  9. 2,4-D amine (Formula 40, Amine 4): A post-emergent herbicide effective on most broadleaf perennial weeds.  It will not control grasses, nor offer any pre-emergent control.  2,4-D should be applied immediately after harvest is complete if emerged broadleaf weeds are a problem.  After application, the bed should be left undisturbed for three to five days, before mowing the leaves off the plants.  This allows time for the material to be taken in by the weeds.  This material can also be used when the plants are dormant (late fall or early spring) to control winter annuals and biennials.  Such applications have been of minimal benefit in northern New England, and sometimes result in injury to the strawberries.  Do not tank mix 2,4-D with sethoxydim (Poast®).
  10. Flumloxazin (Chateau®):  A pre-emergent herbicide for control of broadleaf weeds, including dandelion and shepherd’s purse.  For use in the fall when plants are dormant for control of weeds the following spring.
  11. Pendimethalin (Prowl H20®): A pre-emergent herbicide that may be applied as a band with a shielded sprayer between the rows of strawberries.  No weed control will be provided within the plant rows, and contact of this product on the strawberry plants will cause injury.  May not be applied within 35 days of harvest.

The use of herbicides alone rarely gives complete weed control. Some hand weeding will be necessary.  To provide good weed control throughout the life of a strawberry bed, growers should concentrate on crop rotation and good pre-plant weed control.

Visit the New England Small Fruit Pest Management Guide online for more detailed pest information at: www.umass.edu/fruitadvisor .

Sincerely,

David T. Handley
Vegetable & Small Fruit Specialist

Highmoor Farm                                   Pest Management
P.O. Box 179                                      491 College Avenue
Monmouth, ME  04259                       Orono, ME  04473
207.933.2100                                  1.800.287.0279

Where brand names are used it is for the reader’s information. No endorsement is implied nor is any discrimination intended against products with similar ingredients.  Always consult product label for rates, application instructions and safety precautions.  Users of these products assume all associated risks.

Published and distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914, by the University of Maine Cooperative Extension, the Land Grant University of the state of Maine and the U.S. Department of Agriculture Cooperating.  Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment.

A Member of the University of Maine System