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Late corn has been maturing quickly in much of the state, under good weather conditions. It looks as though there will be a good supply of high quality corn for the holiday weekend. Insect pests remain fairly quiet this week. Vertebrate pest problems have been increasing. Many fields have been visited by hungry birds, skunks, raccoons and deer recently. Next week will be the last regular issue of the Sweet Corn IPM Newsletter for the 2013 season.
European corn borer: Moth catches were up in some locations this week suggesting that a weak second generation of European corn borer may be getting started in southern Maine. These moths could threaten silking corn in fields that are not under a regular spray schedule for corn earworm. Fields in New Gloucester, Nobleboro, North Berwick and Sabattus exceeded the threshold of 5 moths per week in silking corn; but the North Berwick field is under a spray interval for corn earworm, so no additional sprays should be required. Nearly all fields are in silk, so we did not scout for feeding damage this week, but based our recommendations on pheromone trap catches.
Corn earworm: Moth counts were lower in most locations this week. Most traps caught no moths and therefore no spray intervals were recommended this week for silking corn at those sites. A 5-day spray interval was recommended for fields in one of the Dayton sites and Charleston this week. A 6-day spray interval was recommended for silking fields in Auburn, a Dayton site and North Berwick. While the relatively light pressure has meant a relaxed spray schedule for many growers this season, remember that any storm fronts that move up the coast from the south in the coming days and weeks could bring lots of corn earworm with them and change the situation rapidly for any silking corn.
Fall armyworm: Moth counts were higher in some southern and coastal sites, but most caught few or no moths this week. Fall armyworm exceeded the weekly threshold of three moths for silking corn in Biddeford, Cape Elizabeth, Dayton, Monmouth, Nobleboro, Warren and Wells.
Spotted Wing Drosophila Alert: Fruit fly counts are increasing at many sites this week, and more sites are now catching flies. We have more grower reports of larvae in fruit, indicating that even low trap captures signal a significant threat. We recommend that all ripening fruit be protected with an approved insecticide. Regular and repeated treatments are needed to keep fruit from becoming infested. In some locations a 7-day spray interval has not been adequate to prevent infestation, so we have tightened the spray schedule to 4 to 5 days. Chilling fruit to as close to 32ºF immediately after harvest can significantly reduce the activity and emergence of any larvae. Visit our Spotted Wing Drosophila blog for more details.
Understanding and Managing Soils for Healthy Productive Crops: This series will offer farmers strategies to successfully manage soils for long-term productivity. It will take place on Tuesdays, 6:00 PM to 8:00 PM on October 1, 8, 15, 22 and 29, at the Knox and Lincoln Counties Cooperative Extension Office, 377 Manktown Road, Waldoboro, Maine. Cost is $40 per person for the series, or $10 per session. Contact Mark Hutchinson at 207.832.0343 or firstname.lastname@example.org for more information, or visit the UMaine Cooperative Extension Agriculture Programs website.
David T. Handley
Vegetable & 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|
|Auburn||2||0||0||6-day spray interval recommended on all silking corn|
|Biddeford||0||0||10||One spray recommended for FAW on all silking corn|
|Cape Elizabeth I||1||0||10||One spray recommended for FAW on all silking corn|
|Cape Elizabeth II||1||3||7||One spray recommended for FAW on all silking corn|
|Charleston||4||1||1||5-day spray interval recommended on all silking corn|
|Dayton I||2||3||3||6-day spray interval recommended on all silking corn|
|Dayton II||4||2||0||5-day spray interval recommended on all silking corn|
|Farmington||0||4||0||No spray recommended|
|Garland||0||3||1||No spray recommended|
|Levant||0||2||0||No spray recommended|
|Lewiston||0||0||No spray recommended|
|Monmouth||1||1||3||One spray recommended for FAW on all silking corn|
|New Gloucester||1||7||One spray recommended for ECB on all silking corn|
|Nobleboro||0||6||4||One spray recommended for FAW+ECB on all silking corn|
|No. Berwick||3||6||6-day spray interval recommended on all silking corn|
|Oxford||0||1||0||No spray recommended|
|Palmyra||0||1||0||No spray recommended|
|Sabattus||0||6||2||One spray recommended for ECB on all silking corn|
|Wales||0||1||1||No spray recommended|
|Warren||0||1||11||One spray recommended for FAW on all silking corn|
|Wayne||0||2||0||No spray recommended|
|Wells I||0||0||0||No spray recommended|
|Wells II||1||3||7||One spray recommended for FAW 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.
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Image Description: Sweet Corn
Image Description: Corn Harvester
Image Description: European Corn Borer Moth
Image Description: Male Fall Armyworm Moth
Image Description: Spotted Wing Drosophila on Raspberry