Sweet Corn IPM Newsletter No. 8 – August 11, 2017
CORN EARWORM THREAT INCREASES
Fall Armyworm, European Corn Borer Also Increases
A little bit of rain over most of the state helped move corn along, but cooler weather recently has delayed development of younger fields. Harvest is moving into main season varieties and quality continues to look good. Corn earworm numbers are up significantly in most locations, calling for a tightening of spray intervals.
European corn borer: Moth counts have increased in some fields this week, suggesting that a second generation of European corn borer may be getting underway in southern Maine, but feeding injury remains low, and most fields are presently being protected with sprays for corn earworm.
Corn earworm: Moth counts increased significantly in many locations this week, requiring a tightening of spray intervals for silking corn fields. A 6-day spray interval for corn earworm was recommended for silking fields in Monmouth and one Dayton site. A 4-day spray interval was recommended in Auburn, Biddeford, Bowdoinham, one Cape Elizabeth site, one Dayton site, Lewiston, North Berwick, Poland Spring, Wales, and Wells. A 3-day spray interval was recommended at one of the Cape Elizabeth sites.
Fall armyworm: Moth counts are still fairly high, and increased at several sites. Most fields are presently under a spray interval for corn earworm, however, so the silking fields should be adequately protected. A spray for fall armyworm on silking corn was recommended in Oxford. Other sites, including Auburn, Lewiston, Biddeford, Cape Elizabeth, Dayton, Monmouth, New Gloucester, Wales and Wells were also over the 3-moth threshold, but are now on a spray schedule for corn earworm.
David T. Handley
Vegetable and Small Fruit Specialist
Highmoor Farm, P.O. Box 179, 52 US 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
|Recommendations / Comments|
|Auburn||17||0||15||46%||4-day spray interval recommended on all silking corn|
|Biddeford||36||1||11||6%||4-day spray interval recommended on all silking corn|
|Bowdoinham||11||0||0||1%||4-day spray interval recommended on all silking corn|
|Cape Elizabeth I||33||1||15||43%||4-day spray interval recommended on all silking corn|
|Cape Elizabeth II||118||3||22||38%||3-day spray interval recommended on all silking corn|
|Charleston||1||1||0||0%||No spray recommended|
|Dayton I||2||0||0||6-day spray interval recommended on all silking corn|
|Dayton II||37||0||7||11%||4-day spray interval recommended on all silking corn|
|Farmington||0||0||0||0%||No spray recommended|
|Garland||0||2||0||3%||No spray recommended|
|Levant||5||2||3||2%||5-day spray interval recommended on all silking corn|
|Lewiston||24||2||9||1%||4-day spray interval recommended on all silking corn|
|Monmouth||3||0||6||6%||6-day spray interval recommended on all silking corn|
|New Gloucester||49||One spray recommended for FAW on pre-tassel corn|
|North Berwick||38||6||2||2%||4-day spray interval recommended on all silking corn|
|Oxford||1||0||4||0%||One spray recommended for FAW|
|Palmyra||0||0||1||0%||No spray recommended|
|Poland Spring||18||8||2||12%||4-day spray interval recommended on all silking corn|
|Wales||8||0||6||0%||4-day spray interval recommended on all silking corn|
|Wells I||8||0||6||31%||4-day spray interval recommended on all silking corn|
|Wells II||71||0||8||0%||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
|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.
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