Sweet Corn IPM Newsletter No. 11 — September 8, 2023
PEST PRESSURE MODERATE AS SEASON WINDS DOWN
Earworm and Fall Armyworm Threaten Remaining Corn
This will be the final issue of the Sweet Corn IPM Newsletter for the 2023 season. I would like to thank all the growers who participated in the program this year, and our team of IPM scouts, including Chantal Cyr, Ethan Handley and Sean McAuley. Thanks also to Stephanie Wright and Chris Howard for editing and mailing the newsletter, and updating our webpage and blog.
Despite warm temperatures and clear nights, pest activity has remained relatively moderate for this point in the season. Corn earworm remains the biggest threat to silking corn, although fall armyworm has been over threshold in a few fields. Continued warm weather will likely keep the moths active through the remainder of the season.
European corn borer: A second generation of moths appears to be underway in a couple of southern locations, but most fields are no longer seeing this insect as a threat. Moth counts were over the 5-moth/week threshold for silking corn only at one site in Dayton this week. As the season comes to an end, remember that plowing down corn stalks and stubble will destroy the overwintering sites of European corn borer, and can help reduce infestations next season.
Corn earworm: Moth counts were moderate for this late in the season, but still pose a threat to any fresh silking corn remaining in fields this week. Based on this week’s moth counts, a 4-day spray interval for silking corn was recommended for Biddeford, Bowdoinham, Cape Elizabeth, Corinth, Dayton, Monmouth, Wayne and one Wells site. A 5-day spray schedule was recommended for Auburn. A 6-day spray interval was recommended for New Gloucester and one Wells site. Under very high temperatures, moth activity may be higher, so growers should shorten spray intervals by one day if temperatures are over 80F for more than two days.
Fall armyworm: Moth counts were a little higher at several locations, but remain lower than expected for this late in the season. Bowdoinham, Dayton, Monmouth and New Gloucester were over the three-moth threshold for silking corn. Sprays for corn earworm at these sites should also provide control of fall armyworm.
Maine Vegetable & Small Fruit Growers Twilight Meeting
Wednesday, Sept. 13, 5:30 pm, Chick’s Apple & Berry Farm, 571 Main Street, Monmouth, ME.
Join host Paul Peters for a tour of this PYO farm featuring apples, raspberries, blueberries and strawberries, and a discussion of pest issues, including invasive weeds. One pesticide applicator re-certification credit will be available.
University of Maine Highmoor Farm Open House
Thursday, Oct. 5, 5 pm, 52 Rt. 202, Monmouth ME.
Come and view the vegetable variety trials at Highmoor Farm, including artichokes, celery, eggplant, and pumpkins of all shapes, colors and sizes.
David T. Handley
Vegetable & Small Fruit Specialist
P.O. Box 179
52 U.S. Route 202
Monmouth, ME 04259
UMaine Extension Diagnostic Research Lab
Pest Management Unit
17 Godfrey Drive
Orono, ME 04473
|Location||CEW Moths||ECB Moths||FAW Moths||%Feeding Damage||Recommendations / Comments|
|Auburn||6||0||0||—||5-day interval recommended for silking corn|
|Biddeford||10||0||1||—||4-day interval recommended for silking corn|
|Bowdoinham||8||1||3||—||4-day interval recommended for silking corn|
|Cape Elizabeth||10||0||0||—||4-day interval recommended for silking corn|
|Corinth||15||1||1||—||4-day interval recommended for silking corn|
|Dayton I||24||0||8||—||4-day interval recommended for silking corn|
|Dayton II||42||24||9||—||4-day interval recommended for silking corn|
|Lewiston||2||0||0||—||6-day interval recommended for silking corn|
|Monmouth||34||0||9||—||4-day interval recommended for silking corn|
|New Gloucester||2||0||10||—||6-day interval recommended for silking corn|
|Oxford||0||0||0||—||No spray recommended|
|Wayne||10||0||0||—||4-day interval recommended for silking corn|
|Wells I||2||0||0||—||6-day interval recommended for silking corn|
|Wells II||9||3||0||—||4-day 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.
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