Sweet Corn IPM Newsletter No. 7 — August 7, 2026
Corn Earworm Remain High
Silking Corn Requires Protection at All Sites
Situation
Rainfall early in the week provided some much needed relief to dry cornfields, but most sites are still experiencing well below normal rainfall and irrigating wherever possible. Quality of early corn has reportedly been good. As growers move into later planted corn, there is a notable lack of uniformity in stand and maturity in many fields, likely due to heat and moisture stress. Corn earworm numbers continue to be high in nearly all locations this week, and all silking fields require protection.
European corn borer: Moth counts continue to be very low, although we did catch 5 moths at one site in Lewiston, which is over the threshold for silking corn. The site is already under a spray interval for corn earworm, so no additional sprays were recommended. Larval feeding damage continues to be very low, and no sprays were recommended for corn that is not yet silking.
Corn earworm: Moth counts continue to be very high in nearly all coastal and southern locations. All sites are now on a spray interval for fresh silking corn. A 6-day spray interval for silking corn was recommended in Oxford and Palmyra; A 4-day spray interval was recommended for Biddeford, Bowdoinham, Garland, Farmington, Lewiston Wayne and Wells. A 3-day spray interval was recommended in Cape Elizabeth, Dayton, and Gray.
Fall armyworm: Moth numbers in pheromone traps were higher at some locations this week, exceeding the threshold of three per week in silking corn at Biddeford, Bowdoinham, Cape Elizabeth, Gray, Lewiston, Monmouth and one Wells site. All of these locations are either on a spray schedule for corn earworm, which should also control fall army worm, or do not yet have silking corn. Fall armyworm larval feeding damage was generally light and not over the recommended spray threshold.
Western Bean Cutworm: Moth and egg mass counts were variable this week, but mostly lower. However, nearly all sites had potentially damaging populations and a protective silk spray would be recommended if these fields were not presently on a spray program for corn earworm, which should protect silking corn from western bean cutworm as well. No larval feeding injury exceeded the spray threshold for pre-tassel corn.
Squash vine borer: Moth numbers in pheromone traps continued to be low this week, although one site in Oxford did exceed the 5-moth threshold. A spray was recommended for any younger squash, especially summer squash, that might be affected.
Corn leaf aphids are infesting tassels in nearly every field. Although it is unlikely that this will have significant impact on pollination, the colonies of aphids will migrate to the husks and may result in sooty mold. Sprays applied for corn earworm usually control aphids. Sprays specifically for aphids would only be recommended if sooty mold is becoming a problem.
Save the Date!
New England Vegetable and Fruit Conference will take place at the Double Tree in Manchester, New Hampshire. The conference offers 3 days of talks, covering several crops and topics, farmer to farmer sessions and more. Dates for the conference are December 15, 16, 17, 2026.
Registration and schedule information can be found on the New England Vegetable and Fruit Conference website.
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 | 23 | 0 | 4 | 2 | 3% | 4-day spray interval recommended for silking corn |
| Bowdoinham | 29 | 1 | 3 | 8 | 2% | 4-day spray interval recommended for silking corn |
| Cape Elizabeth | 140 | 0 | 7 | 3 | – | 3-day spray interval recommended for silking corn |
| Dayton | 130 | 0 | 0 | 13 | 0% | 3-day spray interval recommended for silking corn |
| Farmington | 16 | 0 | 1 | 16 | – | 4-day spray interval recommended for silking corn |
| Garland | 9 | 0 | 0 | – | 0% | 4-day spray interval recommended for silking corn |
| Gray | 195 | 0 | 16 | 150 | – | 3-day spray interval recommended for silking corn |
| Lewiston I | 84 | 0 | 1 | 10 | – | 4-day spray interval recommended for silking corn |
| Lewiston II | 68 | 5 | 16 | 88 | 0% | 4-day spray interval recommended for silking corn |
| Monmouth | 24 | 0 | 6 | 47 | 5% | No spray recommended (no silking corn) |
| Oxford | 3 | 1 | 2 | 50 | 0% | 6-day spray interval recommended for silking corn |
| Palmyra | 2 | 0 | 1 | – | – | 6-day spray interval recommended for silking corn |
| Wayne | 9 | 0 | 0 | 26 | 1% | 4-day spray interval recommended for silking corn |
| Wells | 44 | 0 | 3 | 9 | 4% | 4-day spray interval recommended for silking corn |
| Wells II | 65 | 0 | 1 | 6 | 0% | 4-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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