Sweet Corn IPM Newsletter No. 3 — July 10, 2026
Earworm Threatens Silking Corn
Spotted Wing Drosophila active in strawberry fields
Situation
The heat continues to push corn development. Rainfall has been inadequate in most areas, and many fields are now being irrigated. Corn earworm has been caught at most locations. Warm nights will increase moth activity, and we expect numbers to keep climbing. Fresh silking corn requires protection in most fields to protect against infestation.
European corn borer: Moth counts remain low in all locations this week. Larval feeding damage in the late whorl and pre-tassel stages was above the threshold only at the Biddeford site. The feeding damage threshold at this stage is 15%.
Corn earworm: Moth captures remain variable from site to site this week as more fields come into silk. A 6-day spray interval for silking corn was recommended in one Wells site; A 5-day spray interval was recommended in Bowdoinham, Cape Elizabeth, Dayton, Garland, and both Lewiston sites.
Fall armyworm: Moths were caught in pheromone traps at three locations this week, but numbers did not exceed the control threshold (3) for silking corn. We have not found fall armyworm feeding damage in the field yet this year.
Squash vine borer: Moth numbers in pheromone traps are over the control threshold at most locations. Sprays to protect pumpkin and squash plants from egg-laying moths were recommended in Lewiston, Gray, Oxford, and Wells. See the New England Vegetable Management Guide for control options.
Spotted Wing Drosophila Alert! Strawberry growers in southern Maine have been finding spotted wing drosophila fruit flies and larvae in ripe strawberry fruit. This is early activity for this pest in Maine. Although it does overwinter here, its numbers typically do not get high enough to impact fruit crops until mid to late August. Growers who still have a good crop of strawberries to harvest should be on the lookout for this pest and begin a spray regimen if it is found. Growers with any ripening raspberries or blueberries should begin a management program now. For more information, visit UMaine Cooperative Extension’s Spotted Wing Drosophila Alert web page.
Save the date!
University of Maine Highmoor Farm Summer Tour, Wednesday, July 29. Orchard tours and tree fruit program, 1-5 pm; Dinner, 5 pm; Vegetable and berry tour, 6-7:30 pm. For more information and registration info, visit the Highmoor Farm Summer Tour web page.
Sincerely,
David T. Handley
UMaine Extension Vegetable & Small Fruit Specialist
Highmoor Farm
P.O. Box 179
52 U.S. Route 202
Monmouth, ME 04259
207.933.2100
UMaine Extension Diagnostic Research Lab
Pest Management Unit
17 Godfrey Drive
Orono, ME 04473
1.800.287.0279
| Location | CEW Moths | ECB Moths | FAW Moths | % Feeding Damage | Recommendations / Comments |
|---|---|---|---|---|---|
| Biddeford | 33% | One spray for ECB | |||
| Bowdoinham | 4 | 0 | 0 | 0% | 5-day spray interval recommended for silking corn |
| Cape Elizabeth | 5 | 0 | 0 | 1% | 5-day spray interval recommended for silking corn |
| Dayton | 6 | 1 | 0 | 4% | 5-day spray interval recommended for silking corn |
| Farmington | 0 | 0 | 0 | 7% | No spray recommended |
| Garland | 3 | 0 | 1 | 1% | 5-day spray interval recommended for silking corn |
| Gray | 1 | 0 | 0 | 0% | No spray recommended |
| Lewiston I | 7 | 0 | 0 | 0% | 5-day spray interval recommended for silking corn |
| Lewiston II | 5 | 0 | 1 | 2% | 5-day spray interval recommended for silking corn |
| Oxford | 0 | 0 | 1 | 0% | No spray recommended |
| Wayne | 1 | 0 | 0 | No spray recommended | |
| Wells | 0 | 0 | 0 | 0% | No spray recommended |
| Wells II | 2 | 0 | 0 | 0% | 6-day spray interval recommended for silking corn |
CEW: Corn earworm (Only fresh silking corn should be sprayed for this insect.)
ECB: European corn borer
FAW: Fall armyworm
| 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:
Explore Integrated Pest Management in Maine — UMaine
Integrated Pest Management — UMass Amherst
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