Sweet Corn IPM Newsletter No. 10 — September 5, 2025
PEST PRESSURE REMAINS MODERATE
Corn Earworm and Fall Armyworm Still a Threat to Late Silking Corn
Situation
The sweet corn season is winding down at most sites, as Labor Day is now behind us, and the very warm temperatures through much of the summer led to early maturity of later plantings. We have pulled our insect monitoring traps from sites that no longer have fresh silking corn and will wind down the IPM program over the next two weeks. Corn earworm and fall armyworm numbers were low at most sites for this late in the season, although counts are variable from site to site. High aphid populations continue to be a problem, resulting in sooty mold on leaves and husks, and attracting wasps.
European corn borer: Only one site (Oxford) recorded any moths this week. No sites reached the 5 moth threshold to protect silking corn.
Corn earworm: Moth numbers were mostly moderate but variable from site to site this week. A six-day spray interval for silking corn was recommended for Bowdoinham, Wayne, and one Wells site. A five-day spray interval was recommended for Dayton and one Wells site; a four-day spray interval was recommended for Cape Elizabeth.
Fall armyworm: Moth counts in pheromone traps exceeded the control threshold (3) for silking corn in Biddeford, Bowdoinham, Cape Elizabeth, Corinth, and one Wells site. A spray to protect silking corn was recommended for Biddeford and Corinth. All other sites are under a spray schedule for earworm, so no additional sprays were recommended. Armyworm feeding damage on pre-tassel corn exceeded the threshold of 15% and sprays were recommended at Bowdoinham.
Western Bean Cutworm: No moths were caught this week.
Aphids: Aphid infestations on tassels and silks continue to be an issue in most fields. If sooty mold is becoming an issue on husks, sprays targeting aphids should be considered. Insecticides registered for aphids on corn include Assail®, Asana®, Warrior® and Lannate®.
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 a grow crop intended for human consumption.
Vegetable and Small Fruit Growers Twilight Meeting: Note the change of date and venue — Bell Farms Inc. in Auburn, Maine is hosting the meeting on Friday, October 3 at 5:00 p.m. For more information, contact the Maine Vegetable and Small Fruit Growers Association.
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 | 1 | 0 | 6 | One spray for FAW on silking corn | |
| Bowdoinham | 3 | 0 | 4 | 16% | 6-day spray interval recommended for silking corn |
| Cape Elizabeth | 15 | 0 | 25 | 4-day spray interval recommended for silking corn | |
| Corinth | 1 | 0 | 18 | 2% | One spray for FAW on silking corn |
| Dayton | 5 | 0 | 0 | 5-day spray interval recommended for silking corn | |
| Monmouth | 1 | 0 | 0 | No spray recommended | |
| Oxford | 0 | 2 | 0 | No spray recommended | |
| Wayne | 3 | 0 | 0 | 6-day spray interval recommended for silking corn | |
| Wells I | 2 | 0 | 0 | 6-day spray interval recommended for silking corn | |
| Wells II | 4 | 0 | 4 | 5-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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