Posts Tagged ‘Maine strawberries’

Strawberry IPM Newsletter No. 6 – July 16, 2014

Wednesday, July 16th, 2014

Strawberries

Strawberry IPM Newsletter No. 6 – July 16, 2014

Click on photos to enlarge.

RENOVATION AND WEED MANAGEMENT ISSUE

Time to Get Your Strawberry Beds Ready for Next Year

Be Ready to Manage Pests in Day-Neutral Strawberries

A cold, nearly snowless period in late December to early January resulted in some moderate winter injury to many strawberry fields around the state this spring.  But favorable spring growing conditions with little to no frost issues resulted in a pretty good crop in most fields. Weather conditions for the harvest seemed often too hot or rainy, especially during the all-important weekends, but customer demand was strong throughout the relatively short season. Pest pressure in most fields was pretty light throughout the season. Insects, including tarnished plant bug and strawberry bud weevil or clipper appeared fairly late and often in low numbers. While spider mites were hardly an issue, cyclamen mites were present in many fields, causing yellowing and dwarfing of affected plants. Root weevils and white grubs were an issue in some fields, especially where problems had been observed last year. Applications of both soil insecticides and parasitic nematodes appear to have helped reduce the problem in most situations. Disease pressure was also light in most fields. Timely fungicide sprays kept gray mold to a minimum, and foliar diseases, such as powdery mildew and leaf spot only began to show up towards the end of the season.

Don’t forget about your strawberries after harvest. Follow the recommended renovation steps listed below for matted row strawberries as soon after harvest as possible; and continue to scout for and manage disease, insect and weed problems as they arise. Some of the more common issues to be alert for during the summer are listed below.

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®, and Pristine®. See the New England Small Fruit Management Guide for detailed descriptions of these diseases and their management.

Powdery Mildew

Powdery Mildew, photo by David Handley

Leaf Spot

Leaf Spot, photo by David Handley

Black root rot is a disease complex which can be brought on by a combination of problems, including nematodes, soil fungi (Rhizoctonia, Pythium), herbicide carryover, and soil compaction. Plants become weak and may wilt and die. Roots on affected plants are black and poorly developed. This tends to be a problem in fields that have been in strawberries constantly for many seasons, and in fields that are under stress in other ways, such as winter injury. Rotating fields to crops other than strawberries for at least three years is an important management strategy for black root rot. Improving soil drainage and breaking up hardpans in the soil may also help. Pre-plant root dips with azoxystrobin (Abound®) may also reduce incidence of black root rot in some fields.

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®, Bifenture®) 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 Management Guide for sources.

Black Vine Weevil

Black Vine Weevil, photo by David Handley

Strawberry Root Weevil Grub

Strawberry Root Weevil Grub, photo by David Handley

White grubs have been an increasing problem in recent years.  The grubs may be the larvae of several species of scarab beetles, including June beetles, rose chafers, Japanese beetles, Asiatic garden beetles and European chafers. The beetles lay their eggs in June and July and the grubs feed on the roots of strawberries from July through mid September. Affected plants will be stunted and wilted and may die during dry periods. Pulling up plants reveals that roots have been chewed off about an inch below the soil line. Sifting through the soil below the plants may reveal the whitish crescent-shaped grubs which can range in size from 3/8 inch to almost 1 ½ inches long, with six legs near the head and a swollen rear-end. The two most effective periods to treat plantings for grubs are in the spring prior to when they pupate (May) and in the late summer when the next generation is actively feeding (late August). Materials should be applied with plenty of water to moist soil to be sure they reach the root zone. Materials currently registered for control of grubs include Platinum® and Admire Pro®. Parasitic nematodes can also provide control of grubs and should be applied with similar timing. Nematodes are very sensitive to ultraviolet light and dehydration and must be applied with lots of water. See the New England Small Fruit Management Guide for sources of parasitic nematodes.

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 David Handley

Potato Leafhopper

Potato Leafhopper, 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®.

MITESTwo-spotted spider mites can increase significantly during the summer. Continue to take leaf samples for spider mites throughout the summer. 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 Management Guide for sources of predatory mites.

Two-spotted Spider Mites

Two-spotted Spider Mites, photo by David Handley

Cyclamen Mite Damage

Cyclamen Mite Damage, photo by David Handley

Cyclamen mites:  Many fields were infested with these mites this spring, and summer may provide a good opportunity to control them. Plants showing weak growth and yellow, crinkled leaves may be infested with cyclamen mite. These 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 with lots of water to be sure that the material is carried down into the crowns.

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 6 weeks of terbacil (Sinbar®) applications, 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 Poastâ, 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. Fall applications may result in injury to the strawberries if the plants are not completely dormant. 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.

 

Strawberry Bed Renovation Review

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. 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 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®).

Mowing Strawberry Leaves

Mowing Strawberry Leaves, photo by David Handley

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 1 ½ inches above the crowns. If the planting is weak, it is recommended that this step of the renovation process be skipped.

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.

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 1 ½ inches of water per week during the growing season.

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:

Strawberry Irrigation

Strawberry Irrigation, photo by David Handley

Sidedressed Strawberry Planting

Sidedressed Strawberry Planting, photo by David Handley

NUTRITION:  Following the application of 40 to 60 pounds of actual nitrogen at renovation, another 20 pounds of nitrogen should 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 UMaine Analytical Lab, 5722 Deering Hall, Rm. 407, University of Maine, Orono, ME 04469-5722, telephone: 207.581.2945.

 

Pest Management for Day-Neutral Strawberries

Most of the important 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 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.

Male and Female Spotted Wing Drosophila Flies

Male (left) and Female (right) Spotted Wing Drosophila, photo by Griffin Dill. Actual size: 2-3 mm.

Spotted wing drosophila (Drosophila suzukii) is a new pest, which is likely to be a concern for day- neutral strawberries, fall raspberries and blueberries. This is a small fruit fly, similar to those that hover around the 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. Infested fruit quickly rots and has no shelf life. This insect 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. Frequently repeated insecticide sprays (1 to 2 per week) may be needed to prevent infestations once the insect is present in a field. Spotted winged drosophila can successfully overwinter here, although it may not build up to damaging levels until late in the summer. We have set out monitoring traps for spotted winged drosophila in fruit plantings around the state to determine the activity of this pest in Maine. However, these traps may not provide adequate early warning, i.e. when we find them in a trap they are probably already established in the field. We have found just a few spotted wing drosophila in Maine over the past two weeks, but not yet in damaging numbers. Products that provide good control of drosophila on strawberries include Radiant®, Brigade®, Danitol®, malathion and Assail®. Keeping fields clean of over-ripe and rotten fruit will also help reduce the incidence of this insect. For more information on identifying spotted wing drosophila and updates on populations around the state, visit our SWD blog.  Other spotted wing drosophila resources can be found on the websites of Michigan State University, Penn State, and University of New Hampshire.

Large Tarnished Plant Bug Nymph

Third Instar Tarnished Plant Bug Nymph, photo by David Handley

Tarnished plant bug:  This is one of the most prevalent and persistent pests of day-neutral strawberries, because 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
Two-spotted Spider Mites

Two-spotted Spider Mites, 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

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 Management Guide.

Gray Mold on Strawberries

Gray Mold on Strawberries, photo by James Dill

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.

Important Reminder for Pesticide Users:  Fruit, vegetable or grain growers who use general use (over-the-counter) pesticides and annually sell more than $1,000 of plants or plant products intended for human consumption will be required to have an Agricultural Basic Pesticide Applicator License by April 15, 2015. In the past, only farmers using restricted use pesticides were required to have a pesticide applicators license. The new law extends the licensing requirement to all commercial growers who use pesticides. Training and testing sessions for unlicensed farmers will be held across the state this fall and winter. For more information contact the Pest Management Office at 1.800.287.0279.

Visit the 2014-2015 New England Small Fruit Management Guide online for more detailed pest information.

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

 

Strawberry IPM Newsletter No. 5 – June 20, 2014

Friday, June 20th, 2014

StrawberriesStrawberry IPM Newsletter No. 5 – June 20, 2014

Click on photos to enlarge.

HARVEST STARTS IN SOUTHERN MAINE

Spider Mites and Leaf Diseases Active

Situation:  Strawberry picking is underway in southern Maine this week, with many farms opening for pick-your-own customers this weekend. Overall, the crop looks good to very good, in spite of some winter injury and a cool, wet start to the season. It also looks as though we will have good weather for opening weekend customers. 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.

Large Tarnished Plant Bug Nymph

Third Instar Tarnished Plant Bug Nymph, photo by David Handley

Tarnished plant bug nymphs were absent in many fields this week and in low numbers wherever they were found. Only one field exceeded the control threshold of 4 flower clusters infested with nymphs out of 30 sampled. If you still have blossoms remaining in your field, it is important to keep scouting for nymphs into the green fruit stage to prevent injury.

Two-spotted spider mites:  Two fields we scouted this week were over the control threshold of 25% of leaves infested; but most fields had very few, if any, mites present. As drier weather sets in, mite populations will likely begin to increase. Continue scouting for mites during the summer after bed renovation, to prevent a build up that could weaken the plants during flower bud development.

Two-spotted Spider Mites

Two-spotted Spider Mites, photo by David Handley

Strawberry Root Weevil Grub

Strawberry Root Weevil Grub, photo by David Handley

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 to control the beetles when their feeding is noticed (usually until mid- to late-July). Grubs are now beginning to pupate in the soil, and the adult weevils will begin to emerge in a few weeks. Look for notching along the leaf edges and the presence of the black or brown snout beetles during the evening. Applications should be made at night when these insects are active, and the highest allowable rate of the insecticide should be used.

Powdery Mildew

Powdery Mildew, photo by David Handley

Leaf Spot on Strawberry Plant

Leaf Spot, photo by David Handley

Diseases:  Dry weather predicted for the upcoming week should provide some relief from the threat of fruit rots, including gray mold and leather rot. However, foliar diseases, including powdery mildew and leaf spot can continue to flourish under drier conditions if infections have already occurred. If you still have significant bloom remaining in the field, you may still need to apply a fungicide to protect against gray mold, especially if rain is predicted in your area, or you plan to overhead irrigate the planting.

Keep an eye out for anthracnose fruit rot as berries begin to ripen in the field.  Infected fruit show sunken patches of brown or black. Whole fruit may suddenly turn soft or dry up to blackened mummies. This is usually a problem when fields have standing water present and warm temperatures. I haven’t seen anthracnose in the fields I have visited so far, but be aware that this could still become a problem. Effective fungicides include Cabrio® and Abound®.

Spraying Pesticides on Raspberries Using Backpack

Spraying Pesticides on Raspberries, photo by Jill Stanley

Important Reminder for Pesticide Users
Fruit, vegetable or grain growers who use general use (over-the-counter) pesticides and annually sell more than $1,000 of plants or plant products intended for human consumption will be required to have an Agricultural Basic Pesticide Applicator License by April 15, 2015. In the past, only farmers using restricted use pesticides were required to have a pesticide applicators license. The new law extends the licensing requirement to all commercial growers who use pesticides. Training and testing sessions for unlicensed farmers will be held across the state this fall and winter. For more information contact the Pest Management Office at 1.800.287.0279.

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 field heat. Place fruit into refrigerated storage quickly and keep it out of direct sunlight. Fruit should be stored at 32°F 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°F 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.

Strawberry Harvest

Strawberry Harvest, photo by David Handley

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 a look at our checklist and 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.

Websites Worth Visiting
If you are looking for information to help diagnose a problem in your strawberries or need a recommendation for a control strategy, the 2013-2014 New England Small Fruit Management Guide is available online. You should also check out Cornell University’s Berry Diagnostic Tool online.

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

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.

Strawberry IPM Newsletter No. 4 – June 13, 2014

Friday, June 13th, 2014

StrawberriesStrawberry IPM Newsletter No. 4 – June 13, 2014

Click on photos to enlarge.

EARLY FIELDS GETTING READY FOR HARVEST

Tarnished Plant Bugs, Spider Mites and Leaf Diseases Active

Situation:  Strawberry development continues to be slow, as we can’t seem to string together more than a couple of warm days before the cool damp weather creeps back in. Despite the clouds, many fields are starting to get a bit dry; although rain predicted for this weekend may bring those fields some needed moisture. Overall, most fields look very good, with good plant vigor and fairly heavy bloom. Turn out for our twilight meeting at Fairwinds Farm in Bowdoinham was very good, and we thank Pete and Cathy Karonis for their hospitality. Many of the strawberry growers there were hoping to start picking next week and perhaps opening for pick-your-own next weekend. It looks like we’ll have a good crop for July 4th.

Strawberry bud weevil or “clipper” is very active in late flowering varieties and raspberries this week. Most early and mid-season varieties are now beyond the point at which clippers can cause significant damage. Two fields scouted this week were over threshold for clipped buds. Remember that clippers will move onto raspberries to clip flower buds after strawberry bloom.

Clipper Beetle on Strawberry Blossom

Clipper Beetle on Strawberry Blossom, photo by David Handley

First Instar Tarnished Plant Bug Nymph

First Instar Tarnished Plant Bug Nymph, photo by David Handley

Tarnished plant bug nymphs are present in most fields this week, but in most cases were not over the threshold of 4 flower clusters infested with nymphs out of 30 sampled. Most of the nymphs found were still in the very small, bright yellow-green phase. It is important to keep scouting for nymphs through the bloom period and into the green fruit stage because feeding damage can still occur, causing misshapen, seedy berries.

Two-spotted spider mites were present in most fields scouted this week but, with one exception, they were well under the threshold of 25% of leaves infested. Cool, damp weather generally keeps mite populations in check naturally, but they can increase rapidly under hot, dry conditions, so it is important to keep scouting for them.

Cyclamen Mite Damage

Cyclamen Mite Damage, photo by David Handley

Cyclamen mites:  We continue to find fields with cyclamen mite infestations. Usually symptoms are first noticed in beds that are two or three years old.   Infested plants show weak growth and yellow, crinkled leaves. The flower stems are small and short and the petals are deformed and sometimes look pink.  The symptoms can be confused with winter injury, herbicide injury or virus infection. Cyclamen mites reside on undeveloped leaves and flower clusters down within the crown of the strawberry plants, and can be very hard to see, even with magnification. Miticide applications must be applied with lots of water (40-100 gals./acre) to be sure that the material reaches the mites.

Sap beetles sometimes become a problem when fruit starts to ripen. 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.

Slug on Strawberry

Slug on Strawberry, photo by James Dill

Slugs may also start feeding on strawberries as they start to ripen. Moist conditions and mulch encourage the presence of slugs. They feed at night, leaving large holes and tunnels in ripening fruit and shiny slime trails on the leaves. Baits such as Deadline® and Sluggo® offer some control of slugs, and should be used prior to fruit ripening. Avoid contacting the developing fruit with the bait. Pay close attention to label instructions and precautions. Slugs overwinter in the egg stage, so baits applied to the fields in mid-September can effectively reduce egg-laying.

Diseases:  Many fields are now past the most susceptible bloom stage for primary infection by Botrytis spores. Fungicides applied during bloom should provide adequate protection against gray mold unless fields get lots of rain post-bloom. If more than one inch of rain has fallen since your last fungicide application, it is likely that the fruit are no longer protected, and another application may be warranted.

Leather rot (Phytopthora cactorum):  Most fields have dried out very well over the past week, reducing the chance of leather rot infections. If you have standing water in your fields during the bloom or early fruit development period, you may want to consider a fungicide application to prevent leather rot. Remember that fungicides applied for gray mold are generally not effective for leather rot. Aliette®, Agri-Phos® or Phostro® are considered most effective.

Powdery mildew:  Warmer, humid weather has increased the symptoms of powdery mildew in fields this week. Many plants are starting to show red streaks on the leaf and flower stems, upward curling leaves, and white, powdery growth on the leaf undersides. Keep an eye out for leaf cupping in your fields and, if you need to apply another fungicide for gray mold, add a material that will also provide control of powdery mildew, such as Pristine®, Topsin-M®, or captan.

Leaf Spot

Leaf Spot, photo by David Handley

Leaf Scorch

Leaf Scorch, photo by David Handley

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. The spots are smaller in the case of scorch, and lack the white centers. Spots may coalesce to turn the leaves purple and brown, 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®, Cabrio®, and Pristine®.

Bird Damage on Strawberry

Bird Damage on Strawberry, photo by David Handley

Birds, specifically cedar waxwings, will soon be moving into fields to feed on ripening fruit. Waxwings often 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 keep them at bay. They are often discouraged once people start to occupy the fields much of the day to harvest. Cedar waxwings are songbirds and are protected by law. They should not be killed. However, the U.S. Fish and Wildlife Service may issue permits for killing birds 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 the 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, 79 Leighton Road in Augusta.

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.

Strawberry IPM Newsletter No. 3 – June 6, 2014

Monday, June 9th, 2014

Strawberries

Strawberry IPM Newsletter No. 3 – June 2014

Click on photos to enlarge.

STRAWBERRY GROWTH SLOW BUT STEADY AS HARVEST APPROACHES

Clippers, Tarnished Plant Bugs, and Spider Mites Active

Vegetable and Berry Growers Twilight Meeting
Wednesday, June 11, 2014 at 5:30 p.m.
Fairwinds Farm, Bowdoinham, Maine

Situation: The temperatures have remained fairly cool with more damp, cloudy days and, as a result, strawberry development has been relatively slow but steady as we head towards harvest time. A later start may be a good thing for pick-your-own fields, as it will better coincide with the end of the school year; but a few days of warm weather would really speed development. Most early varieties are now in the small green fruit stage, while later varieties are still in bloom. Early fields that started under row covers may be picking a few fruit next week.

Twilight Meeting
The University of Maine Cooperative Extension and the Maine Vegetable and Small Fruit Growers Association will hold a twilight meeting at Fairwinds Farm in Bowdoinham on Wednesday, June 11 at 5:30 p.m. Pete and Cathy Karonis grow 10 acres of strawberries and approximately 40 acres of mixed vegetables in fields along the Kennebec River and have a farmstand and greenhouses in Topsham. They will host a tour of their strawberry, raspberry and vegetable plantings, and describe their growing and marketing practices. In addition, we’ll discuss the upcoming season and pest management issues facing vegetable and berry growers this year. One pesticide applicator recertification will be awarded for the meeting. Hold the date! We’ll meet at the strawberry fields in Bowdoinham.

From I-295, take Exit 37. Turn east towards Bowdoinham onto Route 125/138 South. Travel 1.4 miles to the stop sign, then turn left onto Route 24 North/River Road. Travel 0.7 mile and turn right onto Brown’s Point Rd. Go 2.6 miles (road veers to the right and becomes a dirt road) and the farm is on the left, across from 555 Brown’s Point Road. (Use this address for GPS reference. Signs will be posted.) Their contact information is: tel. 207.522.5064 or 207.522.0246, email fairwindsfarm08@gmail.com.

Strawberry bud weevil or “clipper” is still working in fields of late varieties that still have lots of unopened flower buds. Fields that have reached full bloom or beyond no longer need to be scouted for clipper. Damage in most fields remains fairly light, as early varieties went into bloom before clipper became very active. Three of the fields scouted this week were just over threshold for clipped buds, and clippers have been observed in other fields where the damage had not yet reached threshold.

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®.

Clipper Damage on Strawberry Plant

Clipped Flower Buds from Strawberry Clipper, photo by David Handley

Large Tarnished Plant Bug Nymph

Third Instar Tarnished Plant Bug Nymph, photo by David Handley

Tarnished plant bug nymphs were over threshold in two fields scouted this week, but most fields still showed very little tarnished plant bug activity. However, it is important to keep scouting for nymphs throughout the bloom period because they can appear very quickly under warmer, drier conditions. Insecticide options for tarnished plant bug include malathion, Assail®, Brigade®, Bifenture®, Danitol®, and PyGanic®.

Strawberry Rootworm Beetle

Strawberry Rootworm Beetle, photo by David Handley

Strawberry rootworm (not root weevil) adults and feeding injury were reported on strawberry plants last week The adult stage of this insect is a small (1/8”) dark brown beetle. The beetles feed on strawberry leaves during the spring and late summer, causing numerous small holes in the leaves. The adults in fields now will soon lay eggs. The larvae are small grubs that feed on the roots of strawberry plants, causing them to be stunted and weak.  If these beetles and/or feeding injury is prevalent in a field, a treatment is recommended. Sevin 50WP® is registered for control of this pest, and sprays targeted at other insect pests at this time may also control rootworm. Strawberry rootworm should not be confused with root weevil, a larger insect that causes much more serious damage when present in a field.

Two-spotted spider mites were over the threshold (25% of leaves infested) in two locations this week, and smaller populations (under threshold) have been found in most fields. Mites can proliferate rapidly under hot, dry conditions, so it is important to scout for them often. 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).

Cyclamen mites:  Two more fields we’ve scouted have shown symptoms of cyclamen mite injury this week. Infested plants show weak growth and yellow, crinkled leaves. The flower stems are small and short and the petals are deformed and sometimes look pink.  Cyclamen mites are very hard to see, even with magnification. Portal®, Kelthane® or Thionex® 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.

Spittlebug

Spittlebug, photo by David Handley

Spittlebugs: The frothy spittle masses on the leaf and flower stems from spittlebugs usually show up around bloom. Spittlebugs don’t pose a significant threat to the plants, but the spittle masses are a nuisance for 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®.

Diseases: The conditions have been wet enough in most fields to encourage Botrytis infections, which will lead to gray mold once the fruit start to ripen. Two to three sprays of fungicide during bloom are usually required to provide good protection against this disease.

Leather rot (Phytopthora cactorum) is still a concern for fields which have had long periods of standing water during this wet spring, especially if the fields were not mulched last fall. Fungicides applied for gray mold are generally not effective for leather rot. Foliar sprays of Aliette®, Agri-Phos® or Phostrol® applied during bloom or fruit development can help prevent leather rot.

Anthracnose fruit rot is a potential problem when fruit ripens in fields that are wet from irrigation or rain. This fungus disease is favored by warm, humid conditions and can spread rapidly during rains or when fields are irrigated with overhead sprinklers. 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 fungus can survive and multiply on leaves without visible symptoms, appearing suddenly as a fruit rot when the conditions are right. Fungicides such as Cabrio® and Abound® can provide good control of anthracnose.

Powdery Mildew

Powdery Mildew, photo by David Handley

Powdery mildew symptoms of this fungus disease have just started showing up in fields this week. As the weather warms up expect it to become more prevalent. Mildew may first appear as purple or red streaks on the leaf and flower stems. Later, upward curling leaves and white, powdery growth on the undersides becomes evident. Keep an eye out for leaf cupping in your fields as the days start to get warmer.  Pristine®, Cabrio®, Topsin-M®, captan, Procure®, Torino® and JMS Stylet oil® are registered to control powdery mildew.

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

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.

Strawberry IPM Newsletter No. 2 – May 30, 2014

Friday, May 30th, 2014

StrawberriesStrawberry IPM Newsletter No. 2 – May 30, 2014

Click on photos to enlarge.

STRAWBERRY PESTS NOW ACTIVE DESPITE COOL, WET WEATHER

Clippers, Tarnished Plant Bugs, Spider Mites Found in Fields this Week

Strawberry Frost Injury

Frost Injury to Flowers and Leaves, Photo By David Handley

Vegetable and Berry Growers Twilight Meeting
Wednesday, June 11, 2014 at 5:30 p.m.
Fairwinds Farm, Bowdoinham, Maine

Situation: Continued cool wet weather has kept strawberry development at a relatively slow pace.  Fields in southern to mid-state Maine are coming into full bloom for early varieties, while late varieties are just starting to show a few primary blossoms.  The time from bloom to harvest is approximately three weeks, but may take a little longer under extended cool conditions.  Most fields we visited this week showed some moderate winter injury.  Weak plants, especially in areas where the mulch was thin, show browning within the crown tissue, indicative of freeze damage.

Twilight Meeting
The University of Maine Cooperative Extension and the Maine Vegetable and Small Fruit Growers Association will hold a twilight meeting at Fairwinds Farm in Bowdoinham on Wednesday, June 11 at 5:30 p.m.  Pete and Cathy Karonis grow 10 acres of strawberries and approximately 40 acres of mixed vegetables in fields along the Kennebec River and have a farm stand and greenhouses in Topsham.  They will host a tour of their strawberry, raspberry and vegetable plantings, and describe their growing and marketing practices.  In addition, we’ll discuss the upcoming season and pest management issues facing vegetable and berry growers this year.  One pesticide applicator recertification credit will be awarded for the meeting. Hold the date! We’ll give driving directions soon.

Strawberry bud weevil or “clipper” is now active in most of the fields we’ve scouted. Damage so far is very light, suggesting that the adults are feeding on pollen and mating, but they will very soon start laying eggs and clipping buds. If you haven’t yet been looking for clipped buds, now is the time. Insecticide options for clipper include Lorsban®, Brigade®, Bifenture®, Danitol®,  Sevin® and PyGanic®.

Clipper Injury

Clipper Injury, Photo by David Handley

Tarnished Plant Bug Nymph on Strawberry Blossom

Tarnished Plant Bug Nymph on Strawberry Blossom, photo by David Handley

Tarnished plant bug nymphs were found in most of the fields we scouted this week.  The nymphs can be hard to find, especially if the plants are wet. Young nymphs are very small (2 mm), active, yellow-green insects.  It is important to scout for them regularly, as they can appear very quickly. Only one field was over the threshold (4 or more flower clusters infested per 30 sampled). Start scouting any field with open flowers now.  Insecticide options for tarnished plant bug include malathion, Assail®, Brigade®, Bifenture®, Danitol®, and PyGanic®.

Two-spotted Spider Mites

Two-spotted Spider Mites, photo by David Handley

Two-spotted spider mites were over the threshold (25% of leaves infested) in one location this week.  This is surprising given how cold and wet it has been.  Mites typically proliferate under hot, dry conditions, and we often first find them in plantings under row covers.  But plantings that harbored a high mite population last fall are also likely to see a problem with mites in the spring.  Spider mites will reproduce rapidly under warmer temperatures, so it is important to scout for them regularly. 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).

Cyclamen mites:  One two-year old field showed symptoms of cyclamen mite injury this week.  Infested plants show weak growth and yellow, crinkled leaves. These mites are very small 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. Portal®, Kelthane® or Thionex® 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.

Root weevil management
Plants damaged by root weevils should become more obvious in the coming days as the fields dry out and the grubs become more active.  We have not found any additional fields infested since our reports of two fields last week. Infested plants appear weak and stunted, and may wilt during hot days. 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.  Once the adults become active in July, bifenthrin (Brigade®) will provide some control if used at the highest labeled rates.

Diseases: As the fields come into bloom it is time to protect the flowers against infection by spores of the gray mold fungus, Botrytis cinerea. Two to three sprays of fungicide during bloom are typically required to provide good protection against this disease. Remember that fruit infections take place through the flowers, so gray mold control efforts must be focused on the bloom period.

Leather rot (Phytopthora cactorum) may become a problem in fields where standing water is common during bloom and fruit development, especially if the fields were not mulched last fall. Incidence of leather rot can be reduced by applying straw mulch between the rows to prevent berries from touching the soil and reducing soil splashing onto the berries.  Foliar sprays of Aliette®, Agri-Phos® or Phostrol® may be applied during bloom and fruit development to prevent leather rot when there has been excess moisture in a field, especially those with a history of this problem.

Anthracnose fruit rot is a potential problem when fruit ripens in fields that are wet from irrigation or rain.  This fungus disease is favored by warm, humid conditions and can spread rapidly during rains or when fields are irrigated with overhead sprinklers.  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 fungus can survive and multiply on leaves without visible symptoms, appearing suddenly as a fruit rot when the conditions are right.   Fungicides such as Cabrio® and Abound® can provide good control of anthracnose.

Powdery mildew:  We have not yet seen symptoms of this fungus disease in fields.  It tends to be more prevalent under warm, humid conditions. It may first appear as purple or red blotches on the leaf and flower stems. Later, upward curling leaves and white, powdery growth on the undersides of the leaves becomes evident. Check your fields for pinkish purple leaf and flower stem lesions as new leaves emerge. Pristine®, Cabrio®, Topsin-M®, captan, Procure®, Torino® and JMS Stylet oil® are registered to control powdery mildew.

Angular Leaf Spot

Bacterial Angular Leaf Spot, Photo by David Handley

Angular leaf spot was found in one field this week.  This is a bacterial disease characterized by small water-soaked spots on the leaves, which may turn yellow or black. The symptoms start on the lower leaves but spread throughout the foliage when spores are splashed up by rain or irrigation water. Infections can cause blackening of the berry stems and caps. This disease is favored by extended cool, wet weather with night temperatures close to freezing. Irrigating fields for frost protection encourages development and spread of the disease. Hydrogen dioxide (OxiDate®) may also have some activity against angular leaf spot when used on strawberries as part of a gray mold management program.

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.

Strawberry IPM Newsletter No. 7 – July 15, 2013

Tuesday, July 16th, 2013

Strawberries

Strawberry IPM Newsletter No. 7 – July 15, 2013

RENOVATION AND WEED MANAGEMENT ISSUE

Spotted Wing Drosophila, White Grubs Threaten Berries this Summer

The winter of 2012-2013 gave us a cold, snowless start that resulted in some winter injury in exposed strawberry fields. But good snow cover later in the winter kept damage from being severe in most locations. Good growing conditions early in the spring got plants off to a quick start with a few frosts to threaten early blooming varieties. Rain during much of the bloom period raised concerns about pollination, but going into harvest the crop looked pretty good. Unfortunately, the weather just couldn’t cooperate for much of the harvest season, with heavy rain and very hot, humid conditions, especially on weekends, which kept many of the u-pick customers at home. Pickers did come out during the short intervals of decent weather and saved the harvest from being a big loss; and pre-picked sales were good, but for most farms the end result was a season that was only fair. Timely fungicide sprays through the rain provided good protection in most fields, as gray mold was kept to a minimum in spite of all the moisture. Foliar diseases, such as powdery mildew and leaf spot began to show up towards the end of the season. Insect pressure was generally light, although some fields were weakened but white grubs feeding on plant roots.

Don’t forget about your strawberries after harvest.  Follow the recommended renovation steps listed below as soon after harvest as possible; and continue to scout for and manage disease, insect and weed problems as they arise. Some of the more common issues to be alert for during the summer are listed below.

Powdery Mildew

Powdery Mildew, photo by David Handley

Leaf Scorch

Leaf Scorch, 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 New England Small Fruit Management Guide for detailed descriptions of these diseases and their management.

Black root rot is a disease complex which can be brought on by a combination of problems, including nematodes, soil fungi (Rhizoctonia, Pythium), herbicide carryover, and soil compaction. Plants become weak and may wilt and die. Roots on affected plants are black and poorly developed. This tends to be a problem in fields that have been in strawberries constantly for many seasons, and in fields that are under stress in other ways, such as winter injury. Rotating fields to crops other than strawberries for at least three years is an important management strategy for black root rot. Improving soil drainage and breaking up hardpans in the soil may also help. Pre-plant root dips with azoxystrobin (Abound®) may also reduce incidence of black root rot in some fields.

Black Vine Weevil

Black Vine Weevil, photo by David Handley

Strawberry Root Weevil Grub

Strawberry Root Weevil Grub, 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®, Bifenture®) 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 Management Guide for sources.

White Grub

White Grub, Photo by David Handley

White grubs have been a problem in some fields over the past few seasons.  The grubs may be the larvae of several species of scarab beetles, including June beetles, rose chafers, Japanese beetles, Asiatic garden beetles and European chafers. The beetles lay their eggs in June and July and the grubs feed on the roots of strawberries from July through mid September. Affected plants will be stunted and wilted and may die during dry periods. Pulling up plants reveals that roots have been chewed off about an inch below the soil line. Sifting through the soil below the plants may reveal the whitish crescent-shaped grubs which can range in size from 3/8 inch to almost 1 ½ inches long, with six legs near the head and a swollen rear-end. The two most effective periods to treat plantings for grubs are in the spring prior to when they pupate (May) and in the late summer when the next generation is actively feeding (late August). Materials should be applied with plenty of water to moist soil to be sure they reach the root zone. Materials currently registered for control of grubs include Platinum® and Admire Pro®. Parasitic nematodes can also provide control of grubs and should be applied with similar timing. Nematodes are very sensitive to ultraviolet light and dehydration and must be applied with lots of water. See the New England Small Fruit Management Guide for sources of parasitic nematodes.

Strawberry Rootworm Beetle

Strawberry Rootworm Beetle, photo by James Dill

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.

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®.

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 Management Guide for sources of predatory mites.

Two-spotted Spider Mites

Two-spotted Spider Mites, photo by David Handley

Cyclamen Mite Damage

Cyclamen Mite Damage, 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 with 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.

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. Fall applications may result in injury to the strawberries if the plants are not completely dormant. 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.

Strawberry Bed Renovation Review

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. 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®).

Mowing Strawberry Leaves

Mowing Strawberry Leaves, photo by David Handley

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 1 ½ inches above the crowns. If the planting is weak, it is recommended that this step of the renovation process be skipped.

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.

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 1 ½ inches of water per week during the growing season.

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 should 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: Analytical Lab, 5722 Deering Hall, Rm. 407, University of Maine, Orono, ME 04469-5722, telephone: 581.2945.

Strawberry Irrigation

Strawberry Irrigation, photo by David Handley

Sidedressed Strawberry Planting

Sidedressed Strawberry Planting, photo by David Handley

Pest Management for Day-Neutral Strawberries

Most of the important 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 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.

Male and Female Spotted Wing Drosophila Flies

Male (left) and Female (right) Spotted Wing Drosophila, photo by Griffin Dill. Actual size: 2-3 mm.

Spotted wing drosophila (Drosophila suzukii) is a new pest which is likely to be a concern for day-neutral strawberries, fall raspberries and blueberries.  This is a small fruit fly, similar to the type that hover 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 infested Maine berry crops 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) may be needed to prevent infestations once the insect is present in a field. Spotted winged drosophila can successfully overwinter here, although it may not build up to damaging levels until late in the summer. We have set out monitoring traps for spotted winged drosophila in fruit plantings around the state to determine the activity of this pest in Maine. However, these traps are unlikely to provide early warning, i.e. when we find them in a trap they are probably already established in the field. We will be alerting growers when we find them in Maine. We have found a few spotted wing drosophila in Maine this season, but not yet in damaging numbers. Products that provide good control of drosophila on strawberries include Delegate®, Brigade®, Danitol®, and malathion. Keeping fields clean of over-ripe and rotten fruit can also help reduce the incidence of this insect. For information on identifying spotted wing drosophila and making your own monitoring traps, visit the Michigan State University’s Spotted Wing Drosophila website.

First Instar Tarnished Plant Bug Nymph

First Instar Tarnished Plant Bug Nymph, photo by David Handley

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

 

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

 

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 Management Guide.

Gray Mold on Strawberries

Gray Mold on Strawberries, photo by James Dill

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.

Visit the 2012-2013 New England Small Fruit Management Guide online for more detailed pest information.

Reminder:  Highmoor Farm Field Day and Summer Tour will be held on Wednesday, July 31, 2013 from 9:00 a.m. to 4:00 p.m. Registration fee is $20 per person, including lunch, and preregistration is strongly encouraged. For more information, visit the Highmoor Farm website or call 207.933.2100. If you are a person with a disability and will need any accommodations to participate in this program, please call Pam St. Peter at Highmoor Farm, 207.933.2100 or TDD 1.800.287.8957 to discuss your needs at least 7 days prior to this event.

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.

Handley Talks about Strawberry Crop with Press Herald

Thursday, June 20th, 2013

David Handley, a vegetable and small-fruit specialist with the University of Maine Cooperative Extension in Monmouth, spoke with the Portland Press Herald about this year’s strawberry crop. Handley said he expects “the closest thing to a normal year we’ve had in a while as far as plant development is concerned,” and Maine is better off than other northeastern states that have had twice as much rain, which leads to rotting fruit.

Strawberry IPM Newsletter No. 6 – June 14, 2013

Friday, June 14th, 2013

Strawberries

Strawberry IPM Newsletter No. 6 – June 14, 2013

For full page print version, please see link at the bottom. Click on photos to enlarge.

STRAWBERRY HARVEST STARTS SLOW, BUT PROMISING

Wet, Cool Weather Slows Ripening, Elevates Fruit Rot Threat

Situation: Another cool, wet stretch of weather has slowed strawberry ripening this week. Southern growers are hoping to open for general picking this weekend, but may have to wait until next weekend in some fields, although many are now spot picking fruit for farm stands and farmers markets. The crop looks very good in most fields, despite the recent weather and early indications of winter injury and some frost damage.

Gray Mold on Strawberries

Gray Mold on Strawberries, photo by James Dill

Diseases:  Another round of rain this week has kept the potential for gray mold infections very high. For fields that are still in the early post-bloom stage it is important to keep young fruit protected with fungicides under wet conditions. If the last application was made prior to more than one inch of rainfall, an additional fungicide spray should be considered.

Anthracnose fruit rot has been reported in fields in Massachusetts, and will likely threaten fields in Maine as well, due to the recent rains and warmer temperatures. We recommend use of fungicide products that offer control of both gray mold and anthracnose, such as Pristine® or Cabrio®, as we approach harvest time.

Large Tarnished Plant Bug Nymph

Third Instar Tarnished Plant Bug Nymph, photo by David Handley

Tarnished plant bugs will continue to be a problem on later ripening fruit, although development of the nymphs appears to have been hindered by the recent weather. Continue scouting in late ripening fields that still have blossoms or small green fruit for plant bug nymphs and apply a recommended insecticide if the control threshold is exceeded. Pay close attention to pre-harvest intervals of pesticide products as fields begin to ripen. Products registered for control of tarnished plant bug include Assail®, Thionex®, Malathion®, Brigade®, Danitol® and PyGanic®.

Spittlebug

Spittlebug, Photo by David Handley

Spittlebug masses have been noticed in some fields this week. The spittle masses are usually found on the leaf stems just below the leaflets, and annoy pickers who get the spittle on their hands and arms during harvest. Spittlebugs tend to be a greater problem in weedy fields. Pesticides currently registered for spittlebug control include Provado®, Thionex®, Danitol® and Brigade®.

 

Spotted wing drosophila (Drosophila suzukii) is a new pest, introduced into Maine in 2011, which appears to have become established here. This insect may be a concern for late ripening strawberries, and will certainly pose a serious threat to day-neutral strawberries, fall raspberries and blueberries. This is a small “vinegar fly”, similar to those that hover around over ripe fruit in your kitchen. However, this species will lay its eggs on fruit before it ripens, so the fruit will be contaminated with small white maggots just as it is ready to pick. Infested fruit quickly rots and has no shelf life. This species can complete a generation in less than two weeks, with each female laying hundreds of eggs, so millions of flies can be present soon after just a few enter a field.  This makes them very difficult to control, and frequently repeated insecticide sprays (3 to 5 times per week) may be needed to prevent infestations once the insect is present. While the spotted winged drosophila can overwinter in Maine, it may not build up to damaging levels until late in the summer. This could mean that June bearing strawberries will not be threatened, but later ripening fruit such as day-neutral strawberries, raspberries and blueberries will need to be protected.

Male and Female Spotted Wing Drosophila Flies

Male (left) and Female (right) Spotted Wing Drosophila, photo by Griffin Dill. Actual size: 2-3 mm.

A single spotted wing drosophila was caught in a trap in Massachusetts this week. This is not cause for alarm (it’s actually later than the first capture last year), and no controls are being recommended at this time. But it does suggest that this insect will be growing more active in the coming weeks and that populations will start building thereafter. We will be setting out monitoring traps for spotted winged drosophila in fruit plantings around Maine over the next few weeks to gather as much information on it as we can, and determine how much of a threat this pest will pose this season. For more information on this new and important pest, visit Michigan State University’s Spotted Wing Drosophila website. There is a good fact sheet series on this pest available for free download on the Penn State website.

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°F 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°F 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.

Girl with Quarts of Strawberries

 

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.

Hold the Date:  Highmoor Farm Fruit and Vegetable Growers Field Day July 31, 2013
For more information visit the Highmoor Farm webpage.

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

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.

Strawberry IPM Newsletter No. 5 – June 7, 2013

Friday, June 7th, 2013

Strawberries

Strawberry IPM Newsletter No. 5 – June 7, 2013

For full page print version, please see link at the bottom. Click on photos to enlarge.

STRAWBERRY HARVEST BEGINS IN SOUTHERN MAINE

Tarnished Plant Bug Activity High in Some Fields this Week

Situation:  A stretch of fair weather has moved strawberry development along at a more normal pace over the past few days. The heat and storms of last weekend do not appear to have caused any serious issues in strawberry fields we visited. Leaf spot and tarnished plant bugs were the most common problems seen. Harvest is getting underway in some fields that were under row covers this spring. Most fields are now beyond full bloom and most growers are predicting a “normal” opening date for their pick-your-own fields. Overall, most fields appeared very good this week and the crop looks quite promising.

Diseases:  The risk of gray mold infection remains very high, with significant rainfall predicted over the next few days. It is important to keep blossoms and fruit protected with fungicides under wet conditions. If the last application occurred over a week ago, or more than one inch of rain has fallen since the last application, an additional fungicide spray should be considered.

Anthracnose fruit rot also remains a threat as tropical storms often create the wet fields and high temperatures that are conducive to the development of this fruit rot. It may be best to use a fungicide product that offers control of both gray mold and anthracnose, such as Pristine® or Cabrio®.

Leather rot (Phytopthora cactorum) could also appear in fields if standing water is prevalent for an extended time following heavy rains. Aliette®, Agri-Phos® or Phostrol® applied during fruit development can help prevent leather rot when the risk of this disease is high.

Powdery mildew is just starting to appear in some fields this week. This was encouraged by recent warmer weather. Leaves that are cupping upward are the most notable symptom for this fungus disease, and you may also see red streaking on leaf and flower stems. We anticipate that powdery mildew will become more prevalent soon, because it prefers warm, humid conditions. Fungicides for gray mold that also offer control of powdery mildew include Topsin-M® and Pristine®.

Leaf Spot on Strawberry Plant

Leaf Spot, photo by David Handley

Leaf spot/leaf blight infections were noticed in most fields we scouted this week. Leaf spot or leaf blight, caused by the fungus Phomopsis obscurans, was the most common problem. This disease usually appears on mature leaves as small purple or red spots with white or brown centers. Over time the spots may coalesce into a larger lesion, and give the leaf a burned appearance. The disease can spread onto the fruit stems and calyxes, giving them an unattractive reddish-brown discoloration. Leaf scorch is caused by a different fungus, and has been less common this spring. The spots are smaller and don’t have the white or brown centers. The spots often coalesce to turn the leaves purple and necrotic. Strawberry varieties vary greatly in their susceptibility to leaf spot and leaf scorch, with many having at least some resistance. However, under high disease pressure, many will show some symptoms. Fungicides registered for leaf spots include captan, Topsin-M®, Syllit®, Cabrio®, Rally® and Pristine®.

First Instar Tarnished Plant Bug Nymph

First Instar Tarnished Plant Bug Nymph, Photo by David Handley

Tarnished plant bug populations were significantly higher in many fields this week. Half of the fields we scouted were over the control threshold for plant bug nymphs and sprays were recommended. At this time we are finding mostly very small, green, first and second instar nymphs. They can be distinguished from similarly colored aphids because they are much more active, and will run rapidly when disturbed. The nymphs and adults are feeding on flowers and developing fruit and will cause the berries to have hard, seedy ends and other malformations. Products registered for control of tarnished plant bug include Assail®, Thionex®, Malathion®, Brigade®, Danitol® and PyGanic®.

Clipper on Strawberry

Clipper on Strawberry, photo by David Handley

Strawberry bud weevil or “clipper” injury has been noted in several fields this week and we found more live clippers than in any previous scouting trips this year. However, most of the injury was to lower order (late, small) flower buds, so the economic significance of the potential fruit loss is minimal, and no sprays were recommended. If your fields still have late varieties in early bloom, you should continue scouting for clipper and apply controls if significant damage is noted to the buds. Be aware the clippers will move on to raspberries and blackberries and clip off their buds, once the strawberries have come into bloom.

Two-spotted spider mites were found in most locations this week but, with the exception of one field, were well below the control threshold. The predicted wet weather will probably slow further spider mite development, at least temporarily; but we still anticipate that populations will rise when hotter, drier weather arrives.

Sap beetles have been found in two fields this week while scouting for tarnished plant bug. This is not cause for alarm yet, but growers should be aware that they are present and keep an eye out for damage as the berries start to ripen. 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. Assail®, Brigade®, 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.

Birds, specifically cedar waxwings, will soon be moving into fields to feed on ripening fruit. Waxwings often 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. Feeding is reduced 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. The permit is good for one year, so if you have problems this season, consider applying for a permit this winter, to give you the option to kill birds, if necessary, next season. The Wildlife Damage Office has recommendations for managing birds in crops, and some control options available through their office. For more information call the office in Augusta at 207.629.5181. The office is located in the Capital West Business Center at 79 Leighton Road in Augusta.

Hold the date:  Highmoor Farm Fruit and Vegetable Growers Field Day July 31, 2013.

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

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.

 

Strawberry IPM Newsletter No. 4 – May 31, 2013

Friday, May 31st, 2013

Strawberries

Strawberry IPM Newsletter No. 4 – May 31, 2013

For full page print version, please see link at the bottom. Click on photos to enlarge.

WARMER TEMPS SPEED STRAWBERRY DEVELOPMENT

Higher Temps also Likely to Increase Insect and Mite Activity

Situation: Damp weather stretched through most of the week again, but now things are heating up fast, and the sudden change of temperature should hasten fruit ripening. High temperatures may also stress plants, especially those that experienced winter injury, grub feeding, or any other factor that compromised the plants’ ability to take up water. If plants appear to be wilting, dull colored or otherwise stressed, it may be necessary to irrigate if soils have become dry, to help stressed plants prosper through the high temperatures. Early varieties in southern Maine are now beyond full bloom, and are showing green fruit. Later varieties are mostly in bloom, and the bees have been active under the better weather conditions. Fields that were under row covers are starting to show a few ripe fruit and more will be ripening fast over the next few days. Insect activity remains pretty low for the time being, although we are starting to see an increase, which will be enhanced by the higher temperatures.

Gray Mold on Strawberries

Gray Mold on Strawberries, photo by James Dill

Diseases:  The prolonged damp conditions earlier in the week have kept the risk of gray mold infection very high. So, if it has been more than a week since the last fungicide application, or the field has received more than one inch of rain since the last application, it would be best to apply another fungicide spray.

Anthracnose fruit rot is favored by warm temperatures and wet field conditions, a combination many fields will see over the next few days; so consider using a fungicide that will offer control of both gray mold and anthracnose when making your next fungicide application, such as Pristine® or Cabrio®.

Leather rot (Phytopthora cactorum) may also be an issue in fields where standing water has been prevalent this spring. A spray of Aliette®, Agri-Phos® or Phostrol® applied during bloom and fruit development can help prevent leather rot where the risk of this disease is high.

Powdery mildew:  We have not yet seen any significant signs of powdery mildew, but we anticipate it may become more evident soon, because this fungus can proliferate rapidly under warm, humid conditions. Some fungicides sprays for gray mold can also offer good control of powdery mildew, including Topsin-M® and Pristine®

Slime mold:  I have had a report of slime mold from our friends in New Hampshire this week. Slime mold fungi can occur on strawberry plants and mulch when we get very wet, warm weather in the spring or fall. The mold appears as a creamy white or tan colored, jellylike mass growing out of the soil and up onto leaves and flower clusters or just on top of the mulch. The mass is amorphous and may have gray or black fruiting structures covering its surface. The mold dries out to a hard, crusty structure with powdery spores. Slime mold fungi are not parasitic to plants; they just climb them to improve the spread of their spores, but the masses can smother single leaves or fruits and be unsightly. Slime molds disappear when dry weather returns. They do not require any management.

Clipper Damage on Strawberry Plant

Clipped Flower Buds from Strawberry Clipper, photo by David Handley

Strawberry bud weevil or “clipper” is becoming more active as temperatures rise. However, some early blooming varieties have already developed beyond the point where clipper can do significant harm. Most fields had only very light clipper injury in later flowering varieties this week; none of the fields were over the action threshold. Late blooming fields should still be scouted for clipped buds.

Tarnished plant bugs remain fairly scarce this week. We have seen a few adults and some small nymphs in the fields we scouted, but none were over the action threshold. Expect activity to increase as things get drier and warmer.

 

Strawberry Mite Symptoms

Strawberry Mite Symptoms, photo by David Handley

Two-spotted spider mites were found in higher numbers this week, and distributed over a larger area, but all fields were below the action threshold. The extended cool, wet weather likely slowed spider mite development, but we should anticipate that populations will rise under the recent hotter, drier weather.

 

 

 

Spittlebug

Spittlebug, photo by David Handley

Spittlebugs:  Be on the lookout for spittlebug masses in your fields as we approach harvest time. Although we haven’t noted any in fields this week, they may start to appear soon. 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. 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 them. 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®.

Slug on Strawberry

Slug on Strawberry, photo by James Dill

 

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.

 

Highmoor Farm Fruit and Vegetable Growers Field Day July 31, 2013
Plans are well underway for the Highmoor Farm Field Day to be held on Wednesday, July 31. Growers will have an opportunity to tour the fruit and vegetable research plots at the farm, part of the Maine Agricultural and Forest Experiment Station, and hear Extension specialists and guest speakers discuss current research on apples and grapes. University of Maine leaders and state legislators will also be on hand to offer updates on programs and legislation effecting farming in Maine. Please join us for the program, farm tours and lunch. More information will be coming soon.

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.