Sweet Corn IPM Newsletter No. 11 — September 12, 2025
PEST PRESSURE HIGHER IN LATE SEASON CORN
Corn Earworm and Fall Armyworm Numbers Rise Following Recent Rain
Situation
Cooler nights and shorter days have slowed development of late corn. Supply has been spotty as many later plantings matured earlier than expected. Some rain last weekend brought only a little respite from the severe drought we are experiencing but also brought a small wave of corn earworm and fall armyworm to many sites, threatening any corn that is at the silk stage or younger.
European corn borer: No moths were captured at the sites where we still have traps set up.
Corn earworm: Moth numbers were higher at all locations this week, with the exception of Oxford, probably as a result of last weekend’s storm system. A five-day spray interval was recommended for Biddeford, Bowdoinham, Corinth, Dayton, Monmouth and Wayne; a four-day spray interval was recommended for Cape Elizabeth and Wells.
Fall armyworm: Moth counts in pheromone traps exceeded the control threshold (3) for silking corn in Biddeford, Bowdoinham, Cape Elizabeth, Corinth, Monmouth, Corinth, and one Wells site. All sites are under a spray schedule for earworm, so no additional sprays were recommended.
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®.
It’s Soil Testing Time: Early fall is a good time to seed cover crops and is also a great time to take soil samples. Getting your soil tests results before the ground freezes allows time to correct soil pH with additions of lime, and to incorporate any needed nutrients into the soil, such as phosphorus, potassium, or magnesium, and to apply manure to increase organic matter. Fall applications of lime and nutrients (not nitrogen, as it is prone to leaching) are often ideal, because the fields are drier than in the spring, making applications easier, and nutrients will have time to reach the root zone before the plants need them. You can pick up soil test boxes and forms at any county office of the University of Maine Cooperative Extension, or call us here at Highmoor Farm if you’d like us to send you some. For details on soil testing, visit the University of Maine Analytical Laboratory and Soil Testing Service website.
Vegetable and Small Fruit Growers Twilight Meeting: 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 | Recommendations / Comments |
|---|---|---|---|---|
| Biddeford | 5 | 6 | 5-day spray interval recommended for silking corn | |
| Bowdoinham | 7 | 0 | 4 | 5-day spray interval recommended for silking corn |
| Cape Elizabeth | 20* | 0 | 57 | 4-day spray interval recommended for silking corn |
| Corinth | 4 | 0 | 4 | 5-day spray interval recommended for silking corn |
| Dayton | 6 | 0 | 0 | 5-day spray interval recommended for silking corn |
| Oxford | 0 | 0 | 0 | No spray recommended |
| Wayne | 4 | 0 | 5-day spray interval recommended for silking corn | |
| Wells I | 18* | 0 | 4-day spray interval recommended for silking corn | |
| Wells II | 11 | 10 | 4-day spray interval recommended for silking corn |
* Moths damaged by rodent, exact count not possible
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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