Sweet Corn IPM Newsletter No. 5 — July 24, 2026
Early Sweet Corn Harvest Underway
Western Bean Cutworm Numbers Higher, Threaten Pre-tassel-Silking Corn
Situation
Corn started under plastic mulch or rowcovers is now being harvested in southern and coastal regions of the state. Many farms have started irrigating corn fields due to another extended dry spell. Corn earworm numbers were variable from site to site this week, but most fields do require protection for silking corn. Western bean cutworm has become the most prevalent pest this week, and protection has been recommended in several fields.
European corn borer: Moth counts continue to be very low this week, with no sites exceeding the threshold for silking corn (5). Larval feeding damage was not above the 15% threshold at any sites.
Corn earworm: Moth captures were variable this week and mostly lower than last week. A 6-day spray interval for silking corn was recommended in Gray and one Wells site; A 5-day spray interval was recommended in one Wells site, Lewiston and Palmyra. A 4-day spray interval was recommended for Bowdoinham and Cape Elizabeth.
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 Bowdoinham, Cape Elizabeth, Gray and Lewiston. All of these locations are on a spray schedule for corn earworm, which should also control fall army worm, so no additional sprays were recommended. We also found some fall armyworm feeding damage in the field, but none over the recommended spray threshold.
Western Bean Cutworm: We caught moths at nearly all locations where we have traps for this “new” pest. Western bean cutworm moths lay their eggs on the upper side of corn leaves near the whorl. Eggs are small and white in clusters of 50-200. The larvae feed on the foliage and often move into the ears through the silk channels or the husks, similar to fall armyworm. This insect has become an important corn pest in southern and western regions. We are recommending growers follow control thresholds developed in the Midwest, which include protecting pre-tassel-silking corn when more than one egg mass is found or feeding injury exceeds 1% in a 100 plant sample. We are also recommending protection of silking corn if more than 3 moths are caught in a pheromone trap in a week. This week nearly all of the sites were either over the threshold for moths in silking corn or had egg masses present in pre-tassel corn, so sprays were recommended if the field was not under a spray schedule for corn earworm. Sprays for corn earworm should protect silking corn from western bean cutworm as well. The optimal time for controlling Western bean cutworm larvae is during late pre-tassel to tassel, as they move from the leaves into the ears.
Squash vine borer: Moth numbers in pheromone traps were generally lower this week, but were still over the control threshold at most locations. Sprays to protect pumpkin and squash plants from egg-laying moths were recommended in Biddeford, Gray and Oxford. See the New England Vegetable Management Guide for control options.
Save the date!
University of Maine Highmoor Farm Summer Tour will take place on Wednesday, July 29. Orchard tours and tree fruit program is scheduled from 1:00-4:30 p.m. Dinner will begin at 4:30 p.m. and the vegetable and berry tour is from 5:30-7:30 p.m. For more information visit the Highmoor Farm Summer Tour web page.
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 | 0 | 1 | 2 | 5 | 8% | One spray recommended for silking corn |
| Bowdoinham | 12 | 0 | 5 | 8 | 0% | 4-day spray interval recommended for silking corn |
| Cape Elizabeth | 8 | 0 | 5 | 6 | 4% | 4-day spray interval recommended for silking corn |
| Dayton | 1 | 0 | 0 | 4 | 0% | One spray recommended for silking corn |
| Farmington | 0 | 0 | 0 | 7 | 1% | One spray recommended for silking corn |
| Gray | 2 | 0 | 5 | 3 | 0% | 6-day spray interval recommended for silking corn |
| Lewiston I | 7 | 0 | 3 | 0 | 0% | 5-day spray interval recommended for silking corn |
| Lewiston II | 4 | 0 | 1 | 9 | 2% | 5-day spray interval recommended for silking corn |
| Monmouth | 0 | 0 | 1 | 13 | – | No spray recommended (no silking corn) |
| Oxford | 1 | 0 | 0 | 24 | 4% | One spray recommended for silking corn |
| Palmyra | 5 | 0 | 0 | (no data) | 0% | 5-day spray interval recommended for silking corn |
| Wells | 6 | 0 | 0 | 0 | 1% | 5-day spray interval recommended for silking corn |
| Wells II | 3 | 0 | 0 | 4 | 3% | 6-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
Where brand names or company names are used, it is for the reader’s information. No endorsement is implied nor is any discrimination intended against other products with similar ingredients. Always consult product labels for rates, application instructions and safety precautions. Users of these products assume all associated risks.
University of Maine Cooperative Extension is an equal opportunity institution and provider committed to nondiscrimination. For more information, visit extension.umaine.edu/nondiscrimination.