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Cooperative Extension at Highmoor Farm


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Sweet Corn IPM Newsletter No. 11 – August 22, 2012

For full page print version, please see link at the bottom.  Click on photos to enlarge.

CORN EARWORM PRESSURE CONSISTENTLY HIGH ACROSS STATE

Fall Armyworm and ECB Pressure Present, but Remains Low

SITUATION
With continued southerly weather and thunderstorms passing through the state, insect pressure has remained high, mostly due to corn earworm.  At this point, every location is on at least a 4-day spray interval, with some locations on 3-day intervals.  For many growers, the youngest corn has reached the silking stage as the corn season begins to come to a close.  Warm weather will continue to help corn mature rapidly and insect pressure will likely remain relatively high.

European corn borer:  Insect counts have decreased, with only two locations over the 5-moth threshold:  Biddeford and Charleston.  Feeding damage from ECB in whorl to tassel stage corn has been present in all fields scouted, but exceeded the 15% threshold in only two locations (Biddeford and Sabattus) when fall armyworm damage was added to the total.

Corn earworm:  Moth counts remain high in all locations, putting very high pressure on all silking corn.  A 3-day spray interval for fresh silking corn was recommended for Biddeford, one Cape Elizabeth location, Dayton, one Lewiston location, and Sabattus.  A 4-day spray interval was recommended in one Cape Elizabeth location, Charleston, East Corinth, Farmington, Jefferson, Levant, Livermore Falls, Monmouth, New Gloucester, Nobleboro, Oxford, Palmyra, Poland Spring, Wales, Warren, and Wells.  No locations had a moth count low enough for a 5- or 6-day spray interval.

Fall armyworm:  We continue to find feeding damage in southern fields, but only Biddeford and Sabattus were over the threshold when combined with ECB feeding damage.  Moth captures remain low for this time of year, with only one Cape Elizabeth location exceeding the spray threshold of 3 moths in silking corn; but the field is already under a spray schedule for corn earworm so no additional sprays should be needed.  Two fall armyworm moths were caught at Monmouth and Sabattus, and a single moth was caught in Biddeford, Cape Elizabeth, and one Dayton location this week, below threshold for silking corn.  Fall armyworm feeding damage was also found in Cape Elizabeth, New Gloucester, and North Berwick, but was below the 15% threshold.

Other Pests of Note
Aphids:  Some fields are starting to show infestations of aphids on the tassels, silks and husks.  While their feeding is not usually a significant problem, the presence of aphids and the sooty mold that develops on the husks as a result of their waste (called honeydew) is often objectionable to customers.  Sprays, other than the Bt’s or spinosad products, that are used to control the major corn pests also offer control of aphids as well, including Asana®, Capture®, Warrior® and Lannate®.

Sincerely,

David T. Handley
Vegetable & Small Fruit Specialist

Highmoor Farm                      Pest Management Office
P.O. Box 179                          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
% Feeding
Damage
Recommendations / Comments
Biddeford 95 10 1 15% 3-day spray interval for all silking corn
Cape Elizabeth I 162 3 1 All Silk 3-day spray interval for all silking corn
Cape Elizabeth II 85 4 11 6% 4-day spray interval for all silking corn
Charleston 11 5 0 4% 4-day spray interval for all silking corn
Dayton I 118 1 0 All Silk 3-day spray interval for all silking corn
Dayton II 113 0 1 All Silk 3-day spray interval for all silking corn
East Corinth 21 0 0 2% 4-day spray interval for all silking corn
Farmington 14 0 0 All Silk 4-day spray interval for all silking corn
Jefferson 44 0 0 All Silk 4-day spray interval for all silking corn
Levant 54 3 0 6% 4-day spray interval for all silking corn
Lewiston 152 0 0 All Silk 3-day spray interval for all silking corn
Livermore Falls 29 0 0 3% 4-day spray interval for all silking corn
Monmouth 71 0 2 All Silk 4-day spray interval for all silking corn
New Gloucester 30 0 0 9% 4-day spray interval for all silking corn
Nobleboro 20 2 0 1% 4-day spray interval for all silking corn
Oxford 50 0 0 All Silk 4-day spray interval for all silking corn
Palmyra 8 0 0 4% 4-day spray interval for all silking corn
Poland Spring 29 1 0 All Silk 4-day spray interval for all silking corn
Sabattus 145 2 2 16% 3-day spray interval for all silking corn
Wales 16 0 0 3% 4-day spray interval for all silking corn
Warren 83 2 0 All Silk 4-day spray interval for all silking corn
Wells I 50 0 0 All Silk 4-day spray interval for all silking corn
Wells II 89 3 0 All Silk 4-day spray interval for 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:
http://extension.umaine.edu/ipm/
http://www.pestwatch.psu.edu/sweet_corn.htm
http://www.umass.edu/umext/ipm/

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: European Corn Borer Larvae on Ear

Image Description: Corn Earworm Feeding on Corn

Image Description: Fall Armyworm Injury on Corn Leaves

Image Description: Aphids on Corn


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University of Maine Cooperative Extension


Contact Information

Cooperative Extension at Highmoor Farm
52 U.S. Route 202
Monmouth, Maine 04259-0179
Phone: 207.933.2100
The University of Maine
Orono, Maine 04469
207.581.1110
A Member of the University of Maine System