Sweet Corn IPM Newsletter No. 2 — July 2, 2026
Corn Earworm Threatens Early Silking Corn
First Fall Armyworm Moths Caught This Week
Situation
Early planted corn suffered from cold soils at many locations, so germination has been spotty at some sites, but recent warm temperatures have pushed development rapidly. Some fields seeded under clear plastic mulch are just beginning to silk in southern Maine, while most early plantings are at late whorl to pre-tassel.
European corn borer: We have caught very few European corn borer moths so far this season, but we have found larval feeding in late whorl and pre-tassel corn at some sites, still below the recommended spray threshold of 15% injury, so no sprays have been recommended (see table below). Sprays during the pre-tassel stage, when both moths and larvae are present, are good for targeting the larvae before they can move into the protection of the stalks and ears. Rotate the type of insecticide (IRAC Group number) used to prevent insect resistance from developing. Materials registered for controlling European corn borer include Bacillus thuringiensis products (XenTari®, Dipel DF®); Avaunt®, Coragen®, Warrior II®, Lannate®, Baythroid®, Asana®, Radiant®, Delta Gold®, Mustang®, Sevin XLR® and Intrepid®.
Corn earworm: Corn earworm moths have been active this week. This is a somewhat early arrival of this pest, and only a few early corn fields are showing silk, which is what the moths prefer to lay their eggs upon. This pest is only a concern for fields with corn in the silk stage. The moths lay eggs on the fresh silks, and the larvae move directly into the ears of corn. It is recommended that insecticide products in IRAC Group 3A should not be used alone to control CEW due to developing resistance. Combining them with another material from a different IRAC group (e.g. Lannate, Coragen or Blackhawk /Radiant) will improve effectiveness.
Fall armyworm: We caught fall armyworm moths in pheromone traps at two locations this week. We have not yet found any larval feeding damage in the field. Pheromone trap catches of moths indicate if there is a direct threat to silking corn. However, neither site was over the threshold of 3 moths caught when corn is in silk stage. Corn is often on a spray program for corn earworm when fall armyworm is found.
Squash vine borer: One site in Oxford was over the threshold of 5 moths caught in a pheromone trap this week, indicating that egg laying is ongoing at this time. Moths have been caught in several other locations, but numbers have not yet reached threshold. See the New England Vegetable Management Guide for control options.
Potato leafhopper alert: We have been finding leafhopper damage (“hopper burn”) in beans and strawberries this week. Leafhoppers cause leaves to become curled and yellow-streaked. To scout for them, look for small, light green nymphs on the underside of injured leaves. They are about 1/16 inch long. When touched, they will crawl sideways in a crab-like manner. Control options for potato leafhoppers are listed in the New England Vegetable Management Guide.
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 |
|---|---|---|---|---|---|
| Bowdoinham | 2 | 0 | 0 | 3% | No spray recommended (no silking corn) |
| Cape Elizabeth | 3 | 0 | 0 | 0% | No spray recommended (no silking corn) |
| Dayton | 3 | 0 | 0 | 0% | 6-day spray interval recommended for silking corn |
| Farmington | 0 | 0 | 0 | 14% | No spray recommended |
| Gray | 2 | 0 | 1 | 0% | 6-day spray interval recommended for silking corn |
| Lewiston I | 4 | 0 | 0 | 8% | No spray recommended (no silking corn) |
| Lewiston II | 3 | 0 | 0 | 4% | 6-day spray interval recommended for silking corn |
| Oxford | 0 | 0 | 0 | 10% | No spray recommended |
| Wayne | 2 | 0 | 0 | 1% | 6-day spray interval recommended for silking corn |
| Wells | 1 | 1 | 0 | 0% | No spray recommended (no silking corn) |
| Wells II | 0 | 0 | 1 | 6% | No spray recommended |
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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