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Sweet Corn IPM Newsletter No. 12 – August 29, 2012

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

CORN EARWORM PRESSURE LOWER UNDER COOL NIGHTS

Fall Armyworm and European Corn Borer Numbers Remain Low

SITUATION
Recent relatively cool nights indicate a shift in the weather pattern and have resulted in a dramatic drop in corn earworm captures this week.  However, populations are still high enough to keep all silking fields on a regular spray schedule.  As we approach Labor Day and the season starts to wind down, we have very little pressure from either fall armyworm or European corn borer.  Hot weather predicted for the remainder of the week will push remaining corn maturity along rapidly.  Remnants of hurricane Isaac may visit Maine next week and could bring with it a new flush of earworm and armyworm.

European corn borer:  Moth counts are very low this week with no sites exceeding the 5-moth threshold for silking corn.  Feeding damage was also low, with only the North Berwick site exceeding the 15% threshold when it was combined with fall armyworm damage.

Corn earworm:  Moth counts were significantly lower in all locations this week, but pressure still remains moderate to high for many locations.  A 3-day spray interval for fresh silking corn was recommended only for North Berwick.  A 4-day spray interval was recommended for Biddeford, one Cape Elizabeth location, Dayton, Dresden, East Corinth, Levant, Lewiston, Monmouth, Wales, Wayne and one Wells location.  A 5-day spray interval was recommended for one Cape Elizabeth location, New Gloucester, Nobleboro, Oxford, and one Wells location.  A 6-day spray interval was recommended for Charleston, Jefferson, Palmyra, Poland Spring, and Warren.

Fall armyworm:  We continue to find light feeding damage in some fields, but only North Berwick was over the threshold when combined with ECB feeding damage.  Moth captures continue to be very low for this time of year, with no sites exceeding the spray threshold of 3 moths in silking corn.  Two fall armyworm moths were caught at Cape Elizabeth, and one Lewiston location, and single moths were caught in Biddeford, Cape Elizabeth, Dresden, East Corinth, New Gloucester, and Warren.  Fall armyworm feeding damage was found in Biddeford, Cape Elizabeth and New Gloucester, but was below the 15% threshold.  Most remaining fields are silking and under a spray schedule for corn earworm, so field scouting is not necessary.

Spotted Wing Drosophila Update:
Over the last week spotted wing drosophila numbers have risen significantly. Flies are now at their highest levels of the season.  We have also found drosophila maggots infesting blueberry, raspberry, blackberry, elderberry, grape and peach fruit this week.  For those with late fruit crops still to harvest, protection is necessary to prevent infestation by spotted wing drosophila.  Up to this point weekly applications of an allowed insecticide have been adequate, but reports from the field suggest that more frequent applications may be necessary to keep fruit free from maggots.  Growers in southern states have found that a 3 to 5-day spray schedule was needed to prevent infestation.

 

Sincerely,

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
%Feeding Damage Recommendations / Comments
Biddeford 8 1 1 6% 4-day spray interval for all silking corn
Cape Elizabeth I 9 0 2 All silking 4-day spray interval for all silking corn
Cape Elizabeth II 7 0 1 5% 5-day spray interval for all silking corn
Charleston 2 1 0 1% 6-day spray interval for all silking corn
Dayton I 33 0 0 All silking 4-day spray interval for all silking corn
Dayton II 15 0 0 All silking 4-day spray interval for all silking corn
Dresden 32 0 1 All silking 4-day spray interval for all silking corn
East Corinth 16 0 1 0% 4-day spray interval for all silking corn
Jefferson 3 0 0 All silking 6-day spray interval for all silking corn
Levant 11 0 0 2% 4-day spray interval for all silking corn
Lewiston I 47 0 2 All silking 4-day spray interval for all silking corn
Lewiston II 11 1 0 0% 4-day spray interval for all silking corn
Monmouth 40 0 0 All silking 4-day spray interval for all silking corn
New Gloucester 5 0 1 2% 5-day spray interval for all silking corn
Nobleboro 5 0 0 All silking 5-day spray interval for all silking corn
No. Berwick 129 0 0 18% 3-day spray interval for all silking corn
Oxford 5 0 0 All silking 5-day spray interval for all silking corn
Palmyra 2 0 0 All silking 6-day spray interval for all silking corn
Poland Spring 2 0 0 All silking 6-day spray interval for all silking corn
Wales 20 0 0 All silking 4-day spray interval for all silking corn
Warren 2 0 1 All silking 6-day spray interval for all silking corn
Wayne 18 0 0 All silking 4-day spray interval for all silking corn
Wells I 9 0 0 All silking 4-day spray interval for all silking corn
Wells II 6 1 0 All silking 5-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: Corn Earworm Larvae

Image Description: Fall Armyworm on Corn Silk

Image Description: Spotted Wing Drosophila Larva in Blueberry

Image Description: Spotted Wing Drosophila Larvae in Raspberry


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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