This will be the final issue of the Sweet Corn IPM Newsletter for the 2008 season. I would like to thank all of the growers who participated in the program this year, and our team of IPM scouts including Cameron Saucier, Garrett Boyd, Katie Wonch, Vanessa Fereshetian, Kim McNelly, Greg Wonder, Emmett Harrity, Griffin Dill and Sean McAuley. Special thanks, again, go to Ticia Goucher who coordinated the team. We’ll be sending out an evaluation form for this newsletter and our sweet corn IPM program later this fall. Please take the time to fill it out and return it to us. Your input is needed to be sure that this program provides you with the most pertinent, practical and reliable information possible.

SITUATION
The remnants of tropical storm Hannah have come and gone, leaving some corn fields flooded by more than six inches of rain, and bringing more corn earworms into the state. Moth counts were generally higher this week, although not as high as might be expected after a tropical storm. Most fields remaining are nearing harvest and only one or two sprays may be needed to protect them before the season comes to an end. However, growers who still have silking corn in the field should be vigilant, and keep the ears protected.

European Corn Borer: Most of the traps for European corn borer were pulled from the fields last week, but the few we had out caught no moths this week. At this point in the season any threat posed by European corn borer should be managed by sprays applied for corn earworm.

Corn Earworm: Corn earworm moth catches in pheromone traps were mostly higher this week. However, the counts are still fairly low for this time of year, suggesting that this storm did not drag very many moths with it. Southern and coastal farms were generally hit hardest. Unless we see more weather fronts coming up from the south, or have a lot of warm, clear evenings in the near future, I don’t expect the corn earworm pressure to change much for the remainder of the season. No sprays were recommended this week in Monmouth. A 6-day spray schedule was recommended for Garland, Jefferson and Levant. A 5-day spray interval was recommended for Nobleboro, Palmyra, Sabattus and one Wells location. A 4-day spray interval was recommended in Biddeford, Cape Elizabeth, Dayton, Lewiston, New Gloucester, North Berwick, Poland Spring, Warren, Wayne and Wells. There was no 3-day spray interval recommended this week.

Fall Armyworm: Moth activity showed only a slight increase from the storm. Eight locations had enough moths to trigger a spray recommendation (three or more caught in a week), but most are under a spray schedule for corn earworm, which should control both pests. Sprays on silking corn to control fall armyworm were recommended in Dresden and East Corinth.

There’s still time for cover crops!
Plowing down corn stalks and stubble is an important means of managing European corn borer by destroying their over wintering sites. However, late plowing can leave soil exposed and prone to erosion during the winter and spring. Planting winter rye is a good alternative for many fields. Winter rye can often be planted well into September and still produce enough of a cover to prevent erosion. This grass will survive the winter and put on more growth in the early spring. It should be killed by plowing, mowing or herbicide before it goes to seed. Bear in mind that having rye on the field may delay planting in the spring, as you must wait for conditions to be warm and dry enough to plow it in.
 

Sincerely,
David T. Handley
Vegetable & Small Fruit Specialist

Highmoor Farm 
P.O. Box 179 
Monmouth, ME 04259 
(207) 933-2100      

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Do-It-Yourself IPM: To get the most accurate information about the pest situation on your farm you should monitor the fields yourself on a regular basis. Pheromone traps and lures are available that can give you an accurate, early warning of the arrival of all of the major insect pests. Pheromone traps and lures can be purchased from pest management supply companies such as Gempler's in Mt. Horeb, Wisconsin (1-800-382-8473) or Great Lakes IPM in Vestaburg, Michigan (517-268-5693).

To learn more about IPM scouting techniques, insect identification and control thresholds, order the fact sheet Managing Insect Pests of Sweet Corn available from the University of Maine Cooperative Extension. Color pictures are provided to help with insect identification, and a chart with spray thresholds is supplied to post near your sprayer for easy reference. For copies of this free publication contact the Pest Management Office at 1- 800-287-0279.

IPM Web Pages:
http://pmo.umext.maine.edu/default.htm
http://pronewengland.org/
http://www.pestwatch.psu.edu/sweet_corn.htm
http://www.umass.edu/umext/ipm/
http://www.nysipm.cornell.edu/vegetables.html

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Sweet Corn IPM Weekly Scouting Summary
 

CEW: Corn Earworm (only fresh silking corn should be sprayed for this insect)
ECB: European Corn Borer
FAW: Fall Armyworm

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.
 

Corn Earworm Spray Thresholds for Pheromone traps

Thresholds apply only to corn with exposed fresh silk.
Lengthen spray intervals by one day if maximum daily temperature is less than 80°F.