Sweet Corn IPM Newsletter No. 7- August 13, 2021

Sweet Corn
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Sweet Corn IPM Newsletter  No. 7- August 13, 2021

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Fall Armyworm & Western Bean Cutworm Highest Threat to Silking Corn



Corn development has sped up rapidly with the onset of another spell of very warm weather this week.  Harvest is in full swing and later plantings are developing swiftly.  Pest activity remains very low in most locations. Corn earworm activity is especially low, and most fields are seeing the greatest threat from fall armyworm and western bean cutworm. The tropical front moving in late next week may bring in higher pest pressure.


European Corn Borer in Tassel
European Corn Borer in Tassel, photo by David Handley



European corn borer:

No fields were over the 15% control threshold for feeding activity this week. European corn borer moth trap counts were over the silking spray threshold of 5/week at sites in Dayton and Monmouth.





Corn Earworm Moth
Corn Earworm Moth; photo by David Handley

Corn earworm:  

Pheromone trap moth captures were very low throughout the state; only four sites had recommended spray schedules for silking corn. A 4-day spray schedule was recommended for one site in Wells, a 5-day spray schedule was recommended in Lewiston and New Gloucester, and a 6-day spray schedule was recommended in Garland. No other sites required control of corn earworm at this time.


Fall Armyworm Moths
Fall Armyworm Moths (female right, male left); photo by James Dill

Fall armyworm:

Moths counts continue to be fairly low for this time in the season. Six sites were over the threshold of 3 moths per week in silking corn. Sprays to protect silking corn were recommended at: Auburn, Biddeford, Farmington, New Gloucester, one Dayton site and one Wells site. The New Gloucester site should be  protected with the spray schedule recommended for corn earworm. No feeding damage has been found in the fields, but we expect to see it soon.




Western Bean Cutworm Moth
Western Bean Cutworm Moth; photo by Lindsey Ridlon



Western Bean Cutworm:

Moths continue to be widespread, but numbers have retreated from last week, ranging from 0 to 18. We have not yet seen feeding damage from larvae, but we are recommending that silking corn be protected if sprays are not already being applied to control corn earworm and/or fall armyworm.


Three Squash Vine Borer Moths
Three Squash Vine Borer Moths; photo by Lindsey Ridlon



Squash vine borer:

No traps were over the control threshold of 5 moths per week.






Spotted Wing Drosophila Larvae in Raspberry
Spotted Wing Drosophila Larvae in Raspberry; photo by David Handley.

Spotted wing drosophila:

The number of flies caught in traps has increased significantly in raspberry and blueberry fields this week, raising the threat level to any ripening berries. A 7-day spray interval for fields with ripe raspberries, blackberries and blueberries is recommended.  For more information visit our website



Powdery Mildew on Pumpkin Leaf
Powdery Mildew on Pumpkin Leaf, photo by Mark Hutton


Powdery Mildew:

Weather conditions have been very conducive to the development of powdery mildew on pumpkins and squash.  Be on the lookout for symptoms on plants and be ready to protect fields with a registered fungicide.



Plectosporium blight on pumpkin
Plectosporium blight on pumpkin, photo by Mark Hutton


Plectosporium blight:

Plectosporium has been found in a pumpkin field this 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 registered to control Plectosporium.


David T. Handley

Vegetable and Small Fruit Specialist


Highmoor Farm            Pest Management Unit

P.O. Box 179                17 Godfrey Drive

52 U.S. Route 202        Orono, ME  04473

Monmouth, ME  04259

207.933.2100                1.800.287.0279

Sweet Corn IPM Weekly Scouting Summary

Location CEW








Recommendations / Comments
Auburn 0 0 4 0% One spray for FAW on silking corn
Biddeford 0 0 5 4% One spray for FAW on silking corn
Bowdoinham 1 0 0 0% No spray recommended
Cape Elizabeth 0 1 1 0% No spray recommended
Dayton I 0 5 0 0% One spray for ECB on silking corn
Dayton II 0 0 3 0% One spray for FAW on silking corn
Farmington 0 0 3 0% One spray for FAW on silking corn
Garland 2 0 1 2% 6-day spray interval for silking corn
Lewiston 4 0 0 0% 5-day spray interval for silking corn
Monmouth 0 23 0 1% One spray for ECB on silking corn
New Gloucester 4 0 18 0% 5-day spray interval for silking corn
Oxford 0 0 2 8% No spray recommended
Palmyra 1 0 0 1% No spray recommended
Sabattus 1 3 0 0% No spray recommended
Wayne 1 0 0 0% No spray recommended
Wells I 0 0 5 4% One spray for FAW on silking corn
Wells II 9 4 0 3% 4-day spray interval for silking corn

CEW: Corn earworm (Only fresh silking corn should be sprayed for this insect.)

ECB: European corn borer

FAW: Fall armyworm


Corn Earworm Spray Thresholds for Pheromone Traps

Moths caught per week Moths caught per night Spray interval
0.0 to 1.4 0.0 to 0.2 No spray
1.5 to 3.5 0.3 to 0.5 Spray every 6 days
3.6 to 7.0 0.6 to 1.0 Spray every 5 days
7.1 to 91 1.1 to 13.0 Spray every 4 days
More than 91 More than 13 Spray every 3 days

Thresholds apply only to corn with exposed fresh silk. Lengthen spray intervals by one day if maximum daily temperature is less than 80°F.

European Corn Borer Thresholds

Whorl stage: 30% or more of plants scouted show injury.

Pre-tassel-silk: 15% or more of plants scouted show injury.

Silk: 5 or more moths caught in pheromone traps in one week.


IPM Web Pages:

UMaine IPM

Pest Watch


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