CORN EARWORM ACTIVITY INCREASING
Downy Mildew Alert for Cucurbit Crops
With Labor Day in sight, corn harvest will start to wind down soon. Not many fields remain that are not yet in silk. Corn earworm activity continued to increase in most locations, but not dramatically. Fall armyworm counts are spotty, being high in some sites and absent at others. European corn borer moth counts remain very low in nearly all sites. Be alert for symptoms of downy mildew in cucurbit fields.
European corn borer: Moths were caught in Farmington, Wayne and Sabattus this week, but only Sabattus caught enough moths to warrant a spray to protect silking corn, and may indicate that a second generation of European corn borer is getting underway there.
Corn earworm: Moth captures were generally higher and more widespread this week, with most silking fields now needing protection. A 6-day spray interval for corn earworm on silking corn was recommended in Biddeford, Bowdoinham, Dayton, New Gloucester, and Sabattus. A 5-day spray interval was recommended in North Berwick, Oxford, Poland Spring, Wales, Warren and one Wells site. A 4-day spray interval was recommended in Cape Elizabeth, Lewiston and one Wells site. Tropical storm/hurricane “Erica” may track our way in the coming days. If it does, corn earworm numbers may climb rapidly.
Fall armyworm: Moth counts were somewhat higher this week, but only in some locations. Silking fields in Biddeford, Cape Elizabeth, Lewiston, New Gloucester, North Berwick, Oxford, Wales, Warren, and one Wells site were over the control threshold of three moths in silking corn. However, all of these sites were also under a spray recommendation for corn earworm on silking corn, so no additional sprays were required. Larval feeding damage on young corn was fairly low, and only over the threshold of 15% in Biddeford this week.
Downy mildew alert:
Downy mildew on pumpkins, squash, cucumbers and basil has been reported in southern New England and could quickly spread into Maine should weather conditions remain favorable, i.e. hot and humid. Downy mildew first appears as yellow polka dots on the leaves. These spots quickly turn into square brown lesions between the leaf veins. Older leaves curl upwards at the margins, and soon all the foliage in the field dies. The disease spreads and acts quickly, so if you see the yellow polka dots or brown mosaic-like lesions you need to respond immediately with an effective material to get adequate control. Check the New England Vegetable Management Guide for more details, spray materials and precautions. Jude Boucher at University of Connecticut Extension reports that growers there have been getting good results on cucurbit crops with Ranman®, Tanos® and Presidio® fungicides.
Spotted wing drosophila update:
Spotted wing drosophila counts have been rising significantly in some locations this week. Traps should be set up now, if they haven’t been set already. Start protective sprays on any ripening berries once spotted wing drosophila are caught in traps, or any larvae are noticed in the fruit. Check our SWD blog for more information.
David T. Handley
Vegetable and Small Fruit Specialist
Highmoor Farm Pest Management Office
P.O. Box 179 491 College Avenue
Monmouth, ME 04259 Orono, ME 04473
Sweet Corn IPM Weekly Scouting Summary
|Recommendations / Comments|
|Biddeford||2||0||31||34%||6-day spray interval recommended on all silking corn|
|Bowdoinham||3||0||2||6-day spray interval recommended on all silking corn|
|Cape Elizabeth I||13||0||9||4-day spray interval recommended on all silking corn|
|Cape Elizabeth II||13||0||18||0%||4-day spray interval recommended on all silking corn|
|Dayton I||2||0||0||6-day spray interval recommended on all silking corn|
|Dayton II||4||0||0||6-day spray interval recommended on all silking corn|
|Farmington||0||2||1||6%||No spray recommended|
|Lewiston||26||0||8||4-day spray interval recommended on all silking corn|
|New Gloucester||2||0||10||6-day spray interval recommended on all silking corn|
|Nobleboro||0||0||0||0%||No spray recommended|
|No. Berwick||7||0||3||0%||5-day spray interval recommended on all silking corn|
|Oxford||7||0||4||5-day spray interval recommended on all silking corn|
|Poland Spring||5||0||2||5-day spray interval recommended on all silking corn|
|Sabattus||3||32||1||6-day spray interval recommended on all silking corn|
|Wales||6||0||8||2%||5-day spray interval recommended on all silking corn|
|Warren||6||0||20||2%||5-day spray interval recommended on all silking corn|
|Wayne||1||2||0||5%||No spray recommended|
|Wells I||5||0||0||5-day spray interval recommended on all silking corn|
|Wells II||9||0||4||8%||4-day spray interval recommended on all silking corn|
CEW: Corn earworm (Only fresh silking corn should be sprayed for this insect.)
ECB: European corn borer
FAW: Fall armyworm
Corn Earworm Spray Thresholds for Pheromone Traps
|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.
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.
Published and distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914, by the University of Maine Cooperative Extension, the Land Grant University of the State of Maine and the U.S. Department of Agriculture cooperating. Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment.