EARLY SILKING CORN NEEDS PROTECTION

Corn Earworm Threatens Fields in Southern Maine

SITUATION
Hard to believe, but most fields have again seen at least an inch of rain in the past week.  Early stands are very uneven due to the rain and cool temperatures, but we may see some corn ready to harvest in about two weeks.  Many fields also show symptoms of nitrogen and zinc deficiencies, as a result of all the rain and leaching of fertilizers.  We’re seeing apparent breakdown of herbicides as well, and growers may want to review the weed control information in the 2012-2013 New England Vegetable Management Guide to assess post-emergent herbicide options.

European corn borer:  Moth counts continue to be fairly low this week, although with the advent of silking corn in southern Maine we should pay close attention to these counts.  Moths may lay their eggs on the flag leaves of silking corn resulting in larvae entering the ears through the silk channels without leaving any visible signs of feeding on the foliage.  Therefore, if 5 or more European corn borer moths are caught in a trap over a week in the presence of silking corn, a spray to protect the silks is recommended.  We continue to find feeding injury from small larvae in whorl and pre-tassel stage corn, but only fields scouted in Biddeford and Warren were over the recommended spray threshold.  Corn in the whorl stage should be sprayed if fresh feeding injury is found on 30% or more of the plants in a field.  At the pre-tassel stage, the control threshold is lowered to 15%.

European Corn Borer Larvae on Pre-tassel Stage Corn, photo by David Handley

Corn earworm:  Moth counts were low this week, but we’re finding corn earworm in more locations.  Some fields do not yet have silking corn present, so the moths do not represent a significant threat at the moment.  A single spray was recommended for silking fields in Dayton and North Berwick where their first corn earworms were caught.  A 6-day spray interval was recommended for silking fields in New Gloucester, Sabattus, and another Dayton location.

Fall armyworm:  We have not yet caught any fall armyworm moths in our pheromone traps.  However, because most of our recent weather seems to be coming up from the south, we should expect the arrival of this insect, as well as a likely increase in corn earworm populations, in the near future.

Male Fall Armyworm Moth, photo by David Handley

Common armyworm:  Feeding damage from this pest has declined significantly since last week.  It is likely that larvae have started to leave the plants to pupate.

Aphids:  Be on the lookout for infestations of aphids developing on the tassels, silks and husks.  Aphid feeding is not usually a significant problem.  However, black sooty mold often develops on the husks as a result of the waste (called honeydew) aphids deposit, and can render the ears unmarketable.  Insecticide sprays, other than the Bt’s or spinosad products, that are used to control the major corn pests also offer control of aphids as well, including Asana®, Capture®, Warrior® and Lannate®.

Aphids on Corn Ear, photo by David Handley

Japanese beetles are becoming plentiful in southern and mid-state areas. These insects often find their way into corn fields and may feed on the silks of developing ears, causing poor tip fill.  Sprays for corn earworm (except Bt’s) will often control Japanese beetle as well.

Japanese Beetle, photo by Edwin Remsberg, USDA

Sincerely,

David T. Handley
Vegetable & Small Fruit Specialist

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

Sweet Corn IPM Weekly Scouting Summary

European Corn Borer and Common Armyworm Feeding in Southern Maine

SITUATION
The recent hot spell has pushed corn growth along rapidly, and brought us our first corn earworm of the season.  Many early fields are approaching the pre-tassel stage, and should be getting a side dressing of nitrogen, if needed.  Some corn started under plastic in southern Maine is now tasseling and showing some silk.  Soil moisture levels remain pretty good in most locations due to the over abundance of rain earlier.

European corn borer:  We caught just a few European corn borer moths in southern Maine this week, in spite of the warmer temperatures that usually stimulate moth activity.  Corn borer moths are now laying eggs on corn leaves, and we have started finding small larvae feeding in the whorls.  At this time, the feeding damage looks like pinholes in the leaves.  Corn in the whorl stage only needs to be sprayed if fresh feeding injury is found on 30% or more of the plants scouted in a field (30 out of 100 plants sampled).  Once the corn reaches the pre-tassel stage, the control threshold is lowered to 15%.  Pre-tassel fields in Poland Spring and New Gloucester were over the spray threshold for damage this week, and we expect to find more injury soon as more eggs begin to hatch.

European Corn Borer Trap, photo by David Handley

European Corn Borer Moth, photo by David Handley

Corn earworm:  We caught our first corn earworm of the 2012 season in New Gloucester this week.  No moths have been found yet in other locations.New Hampshire has not yet reported any moths, but a few have been caught in Massachusetts.  Corn earworm is only a concern for fields with silking corn.  A spray is recommended to protect silking corn when corn earworm is first detected in a field.  Additional spray recommendations are based on the average number of moths caught in traps per night or per week.  This week, a six-day spray interval is recommended for all silking corn in the New Gloucester field.

Corn Earworm Moth, photo by David Handley

Fall armyworm:  No fall army worm moths have been caught in our pheromone traps this week. New Hampshire and Massachusetts have not yet reported any fall armyworm in their fields.

Common armyworm:  One field in southern Maine was found with over 30% damage from common armyworm larvae this week.  These caterpillars chew large holes in young corn early in the season.  The larvae are light brown with yellow and black stripes running along the body.  With light infestations, the corn may outgrow the injury.  However, when heavy infestations occur, control may be required.

Common Army Worm, photo by Purdue University

Brown marmorated stink bug is a “new” pest from Asia that caused significant damage to sweet corn in southern and Mid-Atlantic states last year.  Although this insect looks similar to our native brown stink bug, it can colonize cornfields in great numbers, piercing the husks and sucking the juices out of the kernels, causing considerable damage.  This species can be distinguished from brown stink bug by small white stripes on the antennae and legs, and by its aggregating behavior.  Several insecticides registered for sweet corn appear to offer good control of this stink bug, if it appears on corn in Maine, including Baythroid® and Lannate®.  Companies are working to get products specifically registered for brown marmorated stink bug on corn and other crops to deal with this new problem.

Sweet Corn IPM Weekly Scouting Summary

2012 SWEET CORN PEST SEASON BEGINS!

European Corn Borer Moths Active, Larvae Feeding in Early Corn

The 2012 University of Maine Cooperative Extension Integrated Pest Management (IPM) program for sweet corn is underway.  More than twenty volunteer farms will be serving as pest monitoring and demonstration sites this year, with fields in North Berwick, Wells, Hollis, Cape Elizabeth, New Gloucester, Poland Spring, Auburn, Lewiston, Sabattus, Dresden, Jefferson, Nobleboro, Warren, Monmouth, Wayne, Oxford, Farmington, Levant, Stillwater, Garland and East Corinth. Pheromone traps are being set up at these farms to monitor the adult (moth) stages of European corn borer, corn earworm and fall armyworm, and we will be scouting these fields for feeding injury by insect larvae.  We will share the information we collect at these sites and management recommendations every week during the season through this newsletter and blog.

European Corn Borer Scouting, photo by David Handley

SITUATION
A spell of warm, dry conditions in late April and early May allowed farmers in southern Maine to begin planting corn early through plastic mulch or under row covers.  Some of this corn is now in the late whorl to pre-tassel stage.  However, the more recent cool, damp conditions has kept development of later plantings very slow, varying from just a few leaves to early whorl stage.  We expect that the relatively mild winter may result in the early emergence of some of the major corn pests, including European corn borer and corn earworm.

European Corn Borer Moth, photo by David Handley

European corn borer:  We are just starting to find European corn borer moths in the pheromone traps around the state, but activity will pick up as warmer evening temperatures arrive.  These moths will be laying eggs on the undersides of corn leaves.  The egg masses are small and look like overlapping fish scales.  European corn borer is the only one of the three major insect pests of corn that can successfully overwinter in Maine, and it is usually the first pest to become a significant problem.  To monitor corn borer, we scout 100 corn plants in each field, examining twenty plants in a row at five different locations.  This sample provides a reasonably accurate estimate of the total amount of injury in a field.  In the early stages, European corn borer feeding damage looks like small “pinholes” in the leaves.  Corn in the whorl stage only needs to be sprayed if fresh feeding injury is found on 30% or more of the plants scouted in a field.  Once the corn reaches the pre-tassel stage, the control threshold is lowered to 15%.  This is because larvae feeding on the later stages are more likely to move into the ears of the plant.  On the tassels, feeding damage first appears as chewing and brown waste found in the small florets.  After the tassel has emerged from the stalk, the larvae chew into the stalk just below it, often causing the tassel to fall over.  Sprays during the pre-tassel stage, when both moths and larvae are present, reduce the opportunity for larvae to move into the stalks and ears of the plant.  Once the larvae are in the stalks they are protected from sprays.  Good spray coverage of the entire plant provides the most effective kill of larvae as they move from one part of the plant to another.  Rotating the type of insecticide used also improves control.  Materials registered for controlling European corn borer include Bacillus thuringiensis products (XenTari®, Dipel DF®), Avaunt®, Coragen®, Warrior®, Lannate®, Baythroid®, Asana®, Radiant®, Delta Gold®,Mustang® Sevin XLR® and Larvin®.  When corn reaches the silk stage, sprays may be based on the number of corn borer moths caught in pheromone traps rather than just feeding injury.  European corn borer moths will lay eggs on flag leaves of silking corn and the larvae can move into the ears without leaving any visible feeding injury that would be noticed when scouting.  Therefore, if more than five moths are caught during a week in a field with silking corn, a spray will be recommended.  Any growers growing varieties of corn genetically modified to produce the Bt toxin (e.g. Bt corn, Attribute® varieties), should not need to spray to control European corn borer.  Very little feeding damage has been found so far on late whorl to pre-tassel corn, and no field has been over the recommended spray threshold.  We can expect more injury to be showing up soon as more eggs begin to hatch.

European Corn Borer Damage, photo by David Handley

Corn earworm:  Pheromone traps are being set up around the state to monitor the arrival of corn earworm.  Corn earworm generally appears in Maine in early July, but the actual date varies greatly.  The arrival of this pest is only a concern for fields with corn in the silk stage.  Fields not yet in silk do not need to be protected from corn earworm.  When corn earworm moths start being caught at a site, all silking corn in the fields should be protected with a spray.  These moths lay eggs on the fresh silks and the larvae move directly into the ears of corn.  When corn earworm moths cannot find silking corn to deposit their eggs on, they may lay eggs on the leaves of younger corn.  The larvae will feed on the foliage and tassels, similar to armyworm, until the ears become available.  When larvae are found feeding on younger corn, the damage is accounted for, along with any borer or armyworm damage, to determine if a spray is warranted.  We will be watching our traps closely to keep you informed as the season progresses.

Corn Earworm Moth, photo by David Handley

Harstack Trap, photo by David Handley

Fall armyworm:  This is usually the last serious corn insect pest to arrive in Maine.  The moths must fly in from southern over-wintering sites, and tend to lay their eggs on the youngest corn available.  When the larvae hatch, they chew large, ragged holes in the leaves, and may bore into developing ears.  Larvae may also move into the ears through the silk channel, behaving similarly to corn earworm.  Pheromone trap catches will indicate if there is a threat to silking corn.  However, corn will usually be on a spray program for corn earworm when fall armyworm is present, and both insects would be controlled.

Male Fall Armyworm Moth, photo by David Handley

Common armyworm alert:  Common armyworm is often found chewing on early corn.  Like fall armyworm, this caterpillar chews large holes in young corn.  The larvae are light brown with yellow and black stripes running along the body.  This insect is usually only present early in the season and the corn can often outgrow the injury.  However, heavy infestations can occur and may require control.  This week heavy injury to field corn plantings by common armyworm has been seen in the Unity area, and states in southern New England have also been reporting heavy common army worm feeding in both field corn and hay crops.  All of the products listed for European corn borer control (above) are also registered for common armyworm.

Common Army Worm, photo by Purdue University

Common stalk borer: This pest can be a problem early in the season, but usually only around the edges of fields.  The injury is similar to European corn borer, but the feeding holes are larger, usually showing as four or five small holes running across the width of a leaf.  The larvae are purple colored with white stripes.  If high numbers of stalk borer are found in pre-tassel stage corn within the field (not just along the edges), include the injury with corn borer to determine if control is needed.  Injury found in whorl stage corn is typically not a concern because these larvae will leave the plant before the ears emerge.

Common Stalk Borer Damage, photo by David Handley

Do-It-Yourself IPM:  To get the most accurate information about the pest situation on your farm you should monitor the fields yourself on a regular basis.  Pheromone traps and lures are available that can give you an accurate, early warning of the arrival of all of the major insect pests.  Traps and lures can be purchased from pest management supply companies such as Gempler’s (1.800.382.8473) or Great Lakes IPM (517.268.5693).

To learn more about IPM scouting techniques, insect identification and control thresholds, order the fact sheet Managing Insect Pests of Sweet Corn available from the University of Maine Cooperative Extension.  Color pictures are provided to help with insect identification, and a chart with spray thresholds is supplied to post near your sprayer for easy reference.  You can download a copy from our website at: http://umaine.edu/ipm/ipddl/publications/5101e/ or call the Pest Management Office at 1.800.287.0279.

Sweet Corn IPM Weekly Scouting Summary

Last Issue for 2011

“IRENE” FLATTENS FIELDS, INCREASES INSECT PRESSURE

All Silking Corn (Still Standing) Requires Protection

SITUATION
Tropical storm Irene toppled many cornfields this week and, although plants rose back up a bit in most fields, spraying and harvest will be difficult, at best.  Usually after the passing of a tropical storm we see corn earworm and fall armyworm moth numbers rise significantly, and this week counts were indeed up at most locations; but the numbers weren’t nearly as bad as we had feared.  All locations require regular sprays on any silking corn remaining, if possible, with the corn in its present state.

Wind Blown Corn Field, photo by David Handley

European corn borer:  Moth counts remained low with no indication of a widespread second generation emerging as the season winds down.  Only three locations were over the threshold for silking corn this week, including Auburn, Oxford and North Berwick; but any threat posed by European corn borer should be managed by sprays applied for corn earworm.

Corn earworm:  Corn earworm moth counts were higher, as would be expected with the passing of a tropical storm; but most locations are on a four-day spray schedule for any fresh silking corn remaining that is upright.  A four-day spray schedule was recommended for silking corn in all locations except Cape Elizabeth, for which a three-day spray interval was recommended due to the very high moth counts there.  No spray intervals longer than four days were recommended for any silking corn remaining.

Corn Earworm Feeding on Corn, photo by David Handley

Fall armyworm:  Fall armyworm activity continues to be very low in nearly all locations, though counts did rise slightly this week.  Five locations exceeded threshold for silking corn with three or more moths, including Biddeford, one Cape Elizabeth location, East Corinth, and New Gloucester.  All of these fields are following a short spray interval for corn earworm, so no additional sprays should be needed.

Flooding and Food Safety:  If your crops were exposed to flood waters of rivers, streams or lakes as a result of the storm, the federal Food and Drug Administration (FDA) states:  Fresh fruits and vegetables that have been inundated by flood waters cannot be adequately cleaned and should be destroyed.  If the edible portion of a crop is exposed to flood waters, it is considered adulterated and should not enter human food channels.  There is no practical method of reconditioning the edible portion of a crop that will provide a reasonable assurance of human food safety.  Crops in proximity to, or exposed to a lesser degree of flooding, where the edible portion of the crop has NOT come in contact with flood waters, need to be evaluated on a case-by-case basis.  Factors to consider include:  the source of flood waters and potential upstream contributors of human pathogens and/or chemical contaminants; type of crop and stage of growth; and how far above the ground does the lowest edible portion grow.

Wet Strawberries, photo by David Handley

Sincerely,

David T. Handley
Vegetable & Small Fruit Specialist

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

AUGUST STORMS BRING CORN EARWORM SWARMS

SITUATION
As the corn season begins to wind down, it is important to remember that the pest situation can change fairly quickly as we see weather patterns changing.  Tropical storms often bring an influx of corn earworm and fall armyworm moths into the state, while high pressure from the north brings cool weather and reduces moth activity.  We have seen a bit of both of these situations in the past couple of weeks, which has meant frequent modifications to many spray programs to maximize spray effectiveness while keeping the total number of sprays as low as possible.

European corn borer:  Moth numbers have risen over threshold for silking corn in some locations; but, with a few exceptions, larval feeding generally remains low.  This week the five-moth threshold was exceeded in Auburn, one Cape Elizabeth location, one Dayton location, Dresden, North Berwick, Sabattus, Wayne, and one Wells location.  However, all of these sites are under a spray schedule for corn earworm, so no additional sprays should be needed.  ECB larval feeding damage was over spray threshold in pre-silking corn (15%) only in both Cape Elizabeth locations and in Lewiston.

European Corn Borer Trap, photo by David Handley

Corn earworm:  Corn earworm trap counts increased around the state this week, increasing spray schedules for silking corn.  A six-day spray schedule was recommended in Farmington.  Five-day spray schedules were recommended in Dayton.  Four-day spray intervals were recommended in Auburn, Biddeford, Corinth, Dresden, East Corinth, Jefferson, Levant, Lewiston, Monmouth, New Gloucester, North Berwick, Oxford, Palmyra, Poland Spring, Readfield, Sabattus, Wales, Wayne, and both Wells locations.  Three-day spray schedules were recommended in both Cape Elizabeth locations, one Dayton location, Nobleboro, and Warren.

Corn Earworm Larvae, photo by David Handley

Fall armyworm:  Fall armyworm activity continues to be very low in nearly all locations, though counts did rise slightly this week.  Only two locations exceeded threshold for silking corn with three or more moths, Biddeford and one Dayton location.  Larval feeding exceeded the 15% of pre-silking plants infested in both Cape Elizabeth locations and in Lewiston.

Adult Fall Armyworm, photo by David Handley

When Should You Stop Spraying?
When a silking cornfield is under a recommended spray interval for corn earworm, we usually recommend that spraying be stopped once the silks have become thoroughly dried and brown.  At this point, corn earworm moths are unlikely to lay eggs on it.  However, if earworm pressure is very high (e.g. 91+ moths per week) and/or fall armyworm moths are over threshold (3+ moths per week), then spraying should probably continue until either the moth counts drop or you reach the required days before harvest (dh) for the product being used.

Airblast Sprayer on Corn, photo by David Handley

Sincerely,

David T. Handley
Vegetable & Small Fruit Specialist

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

CORN EARWORM POPULATIONS STILL ON THE RISE

Corn Rust Found in Several Fields

European corn borer:  Moth numbers have risen over threshold for silking corn in some locations; but, with a few exceptions, larval feeding generally remains low.  This week the five-moth threshold was exceeded in Auburn, Biddeford, one Dayton location, Dresden, North Berwick, Oxford, Readfield, Sabattus, Wayne, and one Wells location.  However, all of these sites are under a spray schedule for corn earworm, so no additional sprays should be needed.  ECB larval feeding damage was over spray threshold in pre-silking corn (15%) only in Biddeford and Jefferson.

European Corn Borer Larvae on Ear, photo by David Handley

Corn earworm:  Corn earworm trap counts increased around the state this week, increasing spray schedules for silking corn.  A six-day spray schedule was recommended in East Corinth.  Five-day spray schedules were recommended in Farmington and Corinth.  Four-day spray intervals were recommended in Auburn, Biddeford, one Cape Elizabeth location, both Dayton locations, Dresden, Jefferson, Levant, Lewiston, Monmouth, New Gloucester, North Berwick, Oxford, Palmyra, Poland Spring, Readfield, Wales, Wayne, and both Wells locations.  Three-day spray schedules were recommended in one Cape Elizabeth location, Nobleboro, and Warren.

Corn Earworm Moth, photo by David Handley

Fall armyworm:  Fall armyworm activity continues to be very low in nearly all locations.  Only single moths were caught this week in Auburn, Biddeford, one Cape Elizabeth location, and Poland Spring.  Two moths were caught in North Berwick.  No locations exceeded threshold for silking corn with three or more moths.  Larval feeding exceeded the 15% of pre-silking plants infested in Cape Elizabeth, Dresden and Poland Spring this week.

Fall Armyworm on Silk, photo by David Handley

Corn Rust:  Rust is a fungus disease that causes reddish-brown pustules to form on the leaves, stalks and husks, reducing the visual quality of the ears.  Severe infections can reduce ear size, especially if they occur prior to tasseling.  Typically, corn rust does not become a problem until late in the season, because it can’t overwinter in Maine and must move in from the south.  A fungicide spray for rust would only be recommended if the infection were noticed in a field prior to tasseling.  Later infections are unlikely to cause enough damage to the crop to justify control measures.  Materials available to control corn rust include Bravo®, Quilt® and maneb/mancozeb.

Rust on Corn, photo by David Handley

Sincerely,

David T. Handley
Vegetable & Small Fruit Specialist

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

CORN EARWORM ACTIVITY RISING IN MOST LOCATIONS

European Corn Borer Numbers Increase in Some Fields

SITUATION
Corn harvest is moving along nicely, although many stands are maturing unevenly due to the variable weather we have been having.  Pest activity, like the recent weather, continues to vary significantly from one location to another, but we are generally seeing an increase in both corn earworm and European corn borer numbers.

European corn borer:  Moth numbers have risen over threshold for silking corn in some mid-state locations; but, with a few exceptions, larval feeding generally remains low.  If more than 5 corn borer moths are caught in a pheromone trap in a week, corn not being sprayed for corn earworm or fall armyworm needs to be protected.  This week the five-moth threshold was exceeded in Auburn, Biddeford, Readfield, Sabattus, and Wayne.  However, all of these sites except Readfield are under a spray schedule for corn earworm, so no additional sprays should be needed.  ECB larval feeding damage was over spray threshold in pre-silking corn (15%) only in Oxford and Poland Spring.

European Corn Borer Moth, photo by David Handley

EARWORM ACTIVITY INCREASING IN MOST LOCATIONS

Armyworm and European Corn Borer Pressure Relatively Light

SITUATION
Much needed rain showers have helped dry fields in some parts of the state, although hail associated with those showers may have caused plant injury in some fields.  Harvest is moving into full swing, with some supply gaps due to rain interfering with planting schedules. Pest activity has increased in some locations, but decreased in others, illustrating the importance of scouting your own fields on a regular basis.  Early predictions for some tropical weather moving up the coast during the next week could mean a new influx of earworm and armyworm moths.  Stay alert!

European corn borer:  Moth numbers remain relatively low around the state this week, and larval feeding in most locations is quite low.  With much of the corn now in silk, remember that if more than 5 moths are caught in a pheromone trap in a week, corn not being sprayed for corn earworm or fall armyworm needs to be protected.  This week the five-moth threshold was exceeded in East Corinth, Oxford and Sabattus.  ECB larval feeding damage was over spray threshold in pre-silking corn (15%) only in Oxford and Poland Spring.

European Corn Borer Entry Hole, photo by David Handley

Corn earworm:  Corn earworm trap counts increased in some fields and decreased in others, perhaps due to the irregular weather conditions we’ve seen from site to site this week.  Overall, more fields were put on tighter spray intervals.  No sprays were recommended in Farmington, Palmyra, Wales and one Wells location.  A six-day spray schedule was recommended for silking corn fields in one Dayton location, Monmouth and Readfield. Five-day spray schedules were recommended in Corinth, one Dayton location, Levant, Lewiston, New Gloucester, North Berwick and Sabattus.  A four-day spray interval was recommended in Biddeford,Cape Elizabeth, Dresden, Jefferson, Nobleboro, Warren, and one Wells location.  Some weather models are predicting we might see some tropical storm activity early next week.  If this proves to be the case, we may also see a significant influx of corn earworm into the state.

Corn Earworm Larvae, photo by David Handley

Fall armyworm:  With just a couple of exceptions, most locations are still seeing very little fall armyworm activity.  The three or more moth trap threshold for silking corn was only exceeded in one Cape Elizabeth location and New Gloucester, but both of these fields are already under a spray interval for corn earworm, which should control armyworm as well.  Two or less moths were caught in traps in Biddeford, one Dayton location, Dresden, Lewiston, Monmouth, Nobleboro, North Berwick, and one Wells location.

Fall Armyworm Injury on Corn Leaves, photo by David Handley

Other Pests of Note:
Corn smut is often observed in fields this time of year.  This fungus disease is easily recognized by the large galls which form in the ears, tassels, and on leaves.  The young galls are silvery-white in color.  When the galls mature they rupture into masses of powdery, black spores.  This fungus tends to infect plants with a prior injury, perhaps from cultivation or insect feeding.  Smut usually affects a few plants in a field and is not considered an economically significant problem.  There is no effective fungicide for corn smut.

Smut on Corn, photo by David Handley

Sincerely,

David T. Handley
Vegetable & Small Fruit Specialist

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

WEATHER CONTINUES TO INCREASE PEST ACTIVITY

Fall Armyworm Activity Begins

SITUATION
Warm nights have pushed the corn along a bit faster with most locations picking early corn.  The weather has also increased moth activity throughout the state.  Corn earworm and corn borer moth activity has been more widespread.  Fall armyworm moths have also made an appearance in a few locations around the state.

European corn borer:  Moth numbers remain steady in most locations this week, showing increased larval feeding in many fields.  This week the five-moth threshold was exceeded in Cape Elizabeth, East Corinth, North Berwick, Oxford, Sabattus and Warren.   ECB larval feeding damage was over spray threshold in pre-silking corn (15%) in Biddeford, Poland Spring, and Warren.

European Corn Borer in Tassel, photo by David Handley

Corn earworm:  Corn earworm trap counts increased slightly with the warm weather this week.  A six-day spray schedule was recommended for silking corn fields in Auburn, one Cape Elizabeth location, one Dayton location, Dresden, Lewiston, New Gloucester, North Berwick, Warren and Wayne.  Five-day spray schedules were recommended in Biddeford, Corinth, one Dayton location, Nobleboro, Palmyra and in one Wells location.  No four-day spray intervals were recommended.  We continue to find corn earworm larvae feeding on the foliage and in the tassels of pre-silking corn.  This injury is added together with the ECB and fall armyworm feeding injury.

Corn Earworm Moth, photo by David Handley

Fall armyworm:  Fall armyworm moths were more widespread this week.  Three or more moths are considered over threshold for silking corn.  Moths were over threshold in one Dayton location and New Gloucester.  Two or less moths were caught in traps in Auburn, one Cape Elizabeth location, one Dayton location, Lewiston, Readfield and Warren.  Larval feeding injury was observed in both Cape Elizabeth locations, and in one Dayton location.  This feeding injury did not exceed the 15% threshold, so no spray was recommended.

Male Fall Armyworm Moth, photo by David Handley

Fall Armyworm Eggs on Corn, photo by David Handley

Other Pests of Note
Powdery Mildew:  We have reports of powdery mildew now showing up in pumpkin and squash plantings.  You should be scouting your pumpkin fields for gray, dusty spots on the upper sides of the leaves.  If more than 10% of plants are showing symptoms, a fungicide should be applied.  Quadris®, Nova®, Pristine®, Topsin-M®, Flint® and Procure® are among the fungicides labeled for the fungus disease.  For more information see the New England Vegetable Management Guide.

Powdery Mildew on Pumpkin Leaf, photo by Mark Hutton

Plectosporium Blight:  Symptoms of Plectosporium have also been found in pumpkin fields in the past week.  This fungus disease causes white flecking in the surface of the fruit and leaves, leading to collapse of the plants and fruit rot.  See the New England Vegetable Management Guide for details.  The fungicides Quadris®, Maneb®, Bravo®, Cabrio® and Flint® are labeled for use on pumpkins to control Plectosporium.

Plectosporium on Pumpkin, photo by University of Connecticut Cooperative Extension

Sincerely,

David T. Handley
Vegetable & Small Fruit Specialist

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