Sweet Corn IPM Newsletter No. 4 — July 16, 2026
Corn Earworm Numbers Increasing
Fall Armyworm Also Threatens Silking Corn
Situation
Plants continue to develop rapidly with warm temperatures and adequate moisture. Harvest of early corn started on plastic mulch or under row covers could begin next week. Corn earworm numbers are now increasing at most locations, and fall armyworm moths have begun to arrive in significant numbers. Western bean cutworm has also made its first appearance this week.
European corn borer: Moth counts remain very low in all locations this week, except for 4 caught in Bowdoinham. This is below the silking corn threshold of 5 moths per week, so no additional control measures were recommended. Larval feeding damage in the late whorl and pre-tassel stage corn was not above the 15% threshold at any site.
Corn earworm: Moth captures were higher at most, but not all sites this week, and spray intervals are now being recommended for silking corn. A 6-day spray interval for silking corn was recommended in Garland, Bowdoinham, one Lewiston site and one Wells site; A 5-day spray interval was recommended in Biddeford, Dayton, and one Lewiston site. A 4-day spray interval was recommended at the Cape Elizabeth site.
Fall armyworm: Moths numbers in pheromone traps were higher at some locations and exceeded the threshold of three per week when silking corn is present at Biddeford, Bowdoinham, Cape Elizabeth, and Lewiston. All these locations are presently on a spray schedule for corn earworm, which should also control fall armyworm, so no additional sprays were recommended. We have not yet found fall armyworm feeding damage in the field.
Squash vine borer: Moth numbers in pheromone traps continue to be over the control threshold at most locations. Sprays to protect pumpkin and squash plants from egg-laying moths were recommended in Biddeford, Lewiston, Gray, Oxford, and Wells. See the New England Vegetable Management Guide for control options.
Western Bean Cutworm: We caught the first moths of the season at several locations this week, including nine moths in Oxford. A spray was recommended there, as the field was not over threshold for CEW or FAW, but was in silk. The larvae of western bean cutworms feed on corn plants and move into the ears through the silk channels or the husks, similar to fall armyworm. Sprays for corn earworm should protect silking corn from western bean cutworm as well. The optimal time for controlling the larvae is late pre-tassel to tassel, when they move from the leaves and stalk into the ears.
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 | WBCW Moths | % Feeding Damage | Recommendations / Comments |
|---|---|---|---|---|---|---|
| Biddeford | 4 | 0 | 6 | 0 | 3% | 5-day spray interval recommended for silking corn |
| Bowdoinham | 2 | 4 | 4 | 0 | 2% | 6-day spray interval recommended for silking corn |
| Cape Elizabeth | 9 | 0 | 6 | 2 | 2% | 4-day spray interval recommended for silking corn |
| Dayton | 6 | 0 | 2 | 3 | 1% | 5-day spray interval recommended for silking corn |
| Farmington | 1 | 0 | 0 | 0 | 0% | No spray recommended |
| Garland | 2 | 2 | 0 | 1% | 6-day spray interval recommended for silking corn | |
| Gray | 0 | 0 | 1 | 0 | 0% | No spray recommended |
| Lewiston I | 4 | 0 | 6 | 1 | 0% | 5-day spray interval recommended for silking corn |
| Lewiston II | 3 | 0 | 4 | 2 | 0% | 6-day spray interval recommended for silking corn |
| Monmouth | 0 | 0 | 0 | 0 | No spray recommended | |
| Oxford | 1 | 1 | 0 | 9 | 0% | One spray recommended for silking corn |
| Palmyra | 0 | 0 | 0 | 1% | No spray recommended | |
| Wells | 0 | 0 | 0 | 0 | 0% | No spray recommended |
| Wells II | 3 | 0 | 0 | 1 | 2% | 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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