Sweet Corn IPM Newsletter No. 11 — September 4, 2026
Corn Earworm, Fall Armyworm Numbers Variable
Most Remaining Corn is at Silk to Harvest Stage
Situation
Most sites are now coming to the end of the sweet corn season, as the latest plantings are now at or near harvest stage. We have begun pulling out our traps at sites where all remaining corn has dried silks and is no longer susceptible to infestation by earworm. However, it is important to note that fall armyworm will still infest corn right up to harvest, with larvae entering through the sides of the ears, often near the tip. Next week will be the last planned issue of the Sweet Corn IPM Newsletter for the 2026 season.
European corn borer: No moths were captured this week, and no larval feeding damage was found in pre-tassel corn.
Corn earworm: Moth counts were variable from site to site this week but similar to last week, with high numbers in Cape Elizabeth and Lewiston and low counts in Wayne and Farmington. Many farms now have only corn with dried silks remaining, which should not be susceptible to earworm unless pressure is very high. A 5-day spray interval for silking corn was recommended for Bowdoinham and Durham. A 4-day spray interval was recommended for Biddeford, Dayton, Monmouth, Oxford and Wells. A 3-day spray interval was recommended for Cape Elizabeth and Lewiston.
Fall armyworm: Moth numbers declined at most sites this week but still exceed the threshold of three moths per week in silking corn at all sites except one Wells location. The Farmington and Wayne site are not presently on a spray interval for corn earworm, so a spray to protect any remaining corn was recommended. Fall armyworm larval feeding damage in pre-tassel corn exceeded the threshold of 12% (for daytime temperatures over 80°) at Biddeford.
Western Bean Cutworm: No moths were caught in our traps this week. Larvae were found in pre-tassel corn in Biddeford, but the site is spraying for fall armyworm.
Post-Harvest Considerations for Soil Health: Plowing down corn stalks after the season can help reduce overwintering European corn borer populations, but the resulting open ground may also lead to significant soil erosion. Plant winter rye after harvest (90 lb./acre) to generate a vegetative cover to prevent erosion. Applying manure in the fall can also be useful for soil building and fertility but it should be applied and incorporated before the soil freezes, or by December 1st. Soil tests will help determine appropriate rates. For example, dairy manure applied at a rate of 20 tons per acre may supply nearly enough nitrogen for a crop of corn. Be sure to follow all food safety precautions for manure applications when applying to a field that will grow a crop intended for human consumption.
Save the Date!
The New England Vegetable & Fruit Conference will be held in Manchester, New Hampshire on December 15, 16, 17, 2026. Registration is open now and program information will be coming soon.
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 | 37 | 0 | 25 | 0 | 67% | 4-day spray interval recommended for silking corn |
| Bowdoinham | 6 | 0 | 19 | 0 | – | 5-day spray interval recommended for silking corn |
| Cape Elizabeth | 125 | 0 | 27 | 0 | – | 3-day spray interval recommended for silking corn |
| Dayton | 47 | 0 | 9 | 0 | – | 4-day spray interval recommended for silking corn |
| Durham | 7 | 0 | 5 | 0 | – | 5-day spray interval recommended for silking corn |
| Farmington | 1 | 0 | 14 | 0 | – | One spray on silking corn for FAW |
| Lewiston | 120 | 0 | 11 | 0 | – | 3-day spray interval recommended for silking corn |
| Monmouth | 25 | 0 | 25 | 0 | – | 4-day spray interval recommended for silking corn |
| Oxford | 27 | 0 | 6 | 0 | – | 4-day spray interval recommended for silking corn |
| Wayne | 1 | 0 | 3 | 0 | – | One spray on silking corn for FAW |
| Wells | 14 | 0 | 0 | 0 | – | 4-day spray interval recommended for silking corn |
| Wells II | 32 | 0 | 3 | 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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