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Sweet Corn IPM Newsletter No. 4 – July 13, 2011

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Sweet Corn

For full page print version, please see link at the bottom.

Early Corn Close to Harvest in Southern Maine

Pest Pressure Moderate on Most Farms

Corn has responded nicely to the recent period of warm weather.  Much of the early planted corn in southern Maine is now in tassel or beginning to silk.  The first few ears of corn from plants started under row covers were harvested this week.  Late-planted fields are still in the whorl to pre-tassel stage, but the continued warm weather outlook should encourage rapid growth.  Pest pressure is moderate in most locations and only a few fields have both silking corn and insect pressure high enough to require regular sprays.

European corn borer:  Moth numbers continue to be relatively low in most locations this week.  European corn borer larvae can move into the ears of silking corn without leaving any visible feeding injury on the plant.  Therefore, if more than five moths are caught in a week in a field with silking corn, a spray is recommended.  This threshold was exceeded in Cape Elizabeth,Oxford, Nobleboro, Sabattus, and Warren, and sprays were recommended.  ECB larval feeding damage was over threshold in pre-tassel stage corn (15%) in Oxford and Sabattus, requiring sprays in the younger corn as well.

European Corn Borer Moth


Corn earworm:  Corn earworm trap counts were relatively low in most locations this week, as more fields come into silk stage.  A six-day spray schedule was recommended for silking corn fields in Readfield.  A five-day spray schedule for silking corn was recommended in Auburn and Dayton.  A four-day spray interval was recommended for one location in Cape Elizabeth.  Single moth captures occurred in East Corinth, Farmington, Lewiston, and Wells; but this population level is not high enough to warrant a spray.

Harstack Trap

Harstack Trap, photo by David Handley

Fall armyworm:  Only one fall armyworm moth was caught in Wales this week, and we have not yet seen any feeding injury from armyworm larvae on young corn.  For silking corn, three or more moths must be caught for a spray to be recommended.  Feeding injury on pre-silking plants is combined with any European corn borer injury to determine if protection is needed.

Wild Turkey Survey:  Wild turkey populations are expanding in Maine and there have been concerns from farmers about turkeys in their fields.  Researchers at the University of Maine at Augusta are investigating the effects of wild turkeys on various agricultural landscapes in Maine and invite all farmers and gardeners to participate in this research by completing a brief on-line survey at:  The objectives of this survey are to understand the attitudes and concerns of Maine farmers and gardeners regarding wild turkeys.  This voluntary survey should take only 5 minutes and participants may skip any question they do not wish to answer.  Surveys of agricultural producers can help to guide research and management decisions regarding wildlife.  We believe this project will produce valuable and practical information for the agricultural community in our state.  If you have any questions or concerns, contact: Christopher Lage, Ph.D., Assistant Professor of Biology, University of Maine at Augusta,

Wild Turkeys in Orchard

Wild Turkeys, photo by Greg Koller

Highmoor Farm Field Day on Thursday, July 21, 2011
Visit the Highmoor webpage or call 207.933.2100 for details.


David T. Handley
Vegetable & Small Fruit Specialist

Highmoor Farm                      Pest Management Office
P.O. Box179                          491 College Ave
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 %ECB Damage Recommendations / Comments
Auburn 7 0 0 7% 5 day spray interval recommended for all silking corn
Biddeford 0 1 0 14% No spray recommended
CapeElizabethI 0 6 0 0% No spray recommended (no silking corn)
CapeElizabeth II 15 0 0 8% 4 day spray interval recommended for all silking corn
CorinthI 0 2 0 1% No spray recommended
DaytonI 1 0 0 0% No spray recommended
DaytonII 6 0 0 8% 5 day spray interval recommended for all silking corn
Dresden 0 4 0 7% No spray recommended
East Corinth 1 3 0 0% No spray recommended
Farmington 1 1 0 0% No spray recommended
Jefferson 0 0 0 0% No spray recommended
Levant 0 3 0 2% No spray recommended
Lewiston 1 2 0 0% No spray recommended
Livermore 0 1 0 4% No spray recommended
NewGloucester 0 0 0 0% No spray recommended
Nobleboro 0 8 0 2% One spray recommended on all silking corn for ECB
North Berwick 0 3 0 12% No spray recommended
Oxford 0 15 0 16% One spray recommended for ECB (pre-tassel – silk)
Palmyra 0 4 0 1% No spray recommended
Poland Spring 1 No spray recommended
Readfield 3 2 0 2% 6 day spray interval recommended for all silking corn
Sabattus 0 6 0 34% One spray recommended for ECB (pre-tassel – silk)
Wales 0 0 1 2% No spray recommended
Warren 0 5 0 8% One spray recommended on all silking corn for ECB
Wells I 1 1 0 0% No spray recommended
Wells II 1 3 0 8% No spray recommended

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.

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.

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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