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CORN EARWORM NUMBERS INCREASING
Highest Threat in Southern Coastal Region
Cooler days and nights have slowed later corn development, but supply and quality still seems to be good. There has been a significant increase in pest activity, but for the moment it is fairly localized in the southern coastal region.
European corn borer: We continue to catch moths in most locations. Although, with the exception of our Sabattus site, the counts are fairly low. It appears that a second generation of corn borer is underway, which could threaten silking corn in fields that are not on a spray schedule for corn earworm. Biddeford, North Berwick, Sabattus, and Warren were over the threshold of 5 moths per week in silking corn. Only the North Berwick site was not also on a spray regime for corn earworm, so a spray was recommended there. European corn borer feeding damage in pre-tassel corn was over the 15% threshold in North Berwick, Biddeford, Cape Elizabeth, Poland Spring and Wayne this week.
Corn earworm: Corn earworm moth counts jumped higher in some sites this week, most notably in the southern coastal region. A 4-day spray interval was recommended for corn earworm on silking fields in Biddeford, Cape Elizabeth, Garland, Wales and one Wells site. A 5-day spray interval was recommended in Monmouth and one Dayton site. A 6-day spray interval was recommended in Farmington, Levant, one Lewiston site, Sabattus, Warren and Wayne.
Fall armyworm: Most trapping sites had few, if any moths this week, although feeding damage from larvae has increased in some fields. Fields in Biddeford, Cape Elizabeth, Farmington, Monmouth, Nobleboro, and one Wells site exceeded the threshold of 3 moths per week in silking corn. However, only the Nobleboro site was not on a spray regime for corn earworm. Fall armyworm feeding damage on plants exceeded the 15% damage threshold alone, or in combination with European corn borer feeding, in Biddeford, Dayton and Warren this week.
Corn leaf aphids may infest corn plants in fields that have not recently been sprayed for other pests. Colonies of these small, bluish-green insects can nearly cover the tassels, stalks and husks. The waste aphids excrete on the plants, called “honeydew” stimulates the development of sooty mold fungus. This dark, slimy fungus can coat the surface of the husks, greatly reducing the visual appearance of the ears. Sprays applied for corn earworm will usually also control aphids. A spray for aphids would only be recommended if sooty mold is becoming a problem.
Pesticide disposal: This October, the Maine Board of Pesticides Control (BPC) and the Maine Department of Environmental Protection will offer free disposal of banned or unusable pesticides. Collection will occur at sites located in Presque Isle, Bangor, Augusta and Portland. To qualify, people must register by September 26, 2014. Registration is mandatory; drop-ins will not be permitted. To register or get details and important information about the temporary storage and transportation of obsolete pesticides, go to the BPC web site at http://www.thinkfirstspraylast.org and click on Obsolete Pesticide Collection, or call 207-287-2731.
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|
|Biddeford||35||5||3||36%||4-day spray interval recommended on all silking corn|
|Cape Elizabeth I||72||4||0||4-day spray interval recommended on all silking corn|
|Cape Elizabeth II||67||4||9||29%||4-day spray interval recommended on all silking corn|
|Charleston||0||1||0||No spray recommended|
|Dayton I||0||0||0||No spray recommended|
|Dayton II||4||3||0||29%||5-day spray interval recommended on all silking corn|
|Farmington||2||1||4||6-day spray interval recommended on all silking corn|
|Garland||9||0||0||1%||4-day spray interval recommended on all silking corn|
|Levant||2||0||0||2%||6-day spray interval recommended on all silking corn|
|Lewiston I||2||3||0||6-day spray interval recommended on all silking corn|
|Lewiston II||0||4||0||7%||No spray recommended|
|Monmouth||5||3||10||0%||5-day spray interval recommended on all silking corn|
|Nobleboro||0||2||4||One spray recommended for FAW on silking corn|
|No. Berwick||0||6||1||25%||One spray recommended for ECB on silking corn|
|Oxford||0||2||0||3%||No spray recommended|
|Palmyra||0||0||0||No spray recommended|
|Poland Spring||0||0||0||6%||No spray recommended|
|Sabattus||3||29||0||6-day spray interval recommended on all silking corn|
|Wales||11||1||1||4-day spray interval recommended on all silking corn|
|Warren||2||10||2||37%||6-day spray interval recommended on all silking corn|
|Wayne||3||1||0||27%||6-day spray interval recommended on all silking corn|
|Wells I||1||0||1||0%||No spray recommended|
|Wells II||15||3||4||11%||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.
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