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Sweet Corn IPM Newsletter No. 8 – August 11, 2017

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Sweet CornSweet Corn IPM Newsletter No 8 – August 11, 2017

Click on photos to enlarge.

CORN EARWORM THREAT INCREASES  

Fall Armyworm, European Corn Borer Also Increases

SITUATION
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.

Corn Earworm Larvae

Corn Earworm Larvae, photo by David Handley

Fall Armyworm on Corn Leaf

Fall Armyworm on Corn Leaf, photo by David Handley

 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.

Sincerely,

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
207.933.2100                           1.800.287.0279

Sweet Corn IPM Weekly Scouting Summary

Location CEW
Moths
ECB
Moths
FAW
Moths
%Feeding
Damage
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

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.

IPM Web Pages :

UMaine Cooperative Extension IPM
Penn State Sweet Corn IPM
UMass Extension IPM Programs

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.

The University of Maine is an equal opportunity/affirmative action institution.

 

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