Will Seed-Attacking Insects Be A Problem?

For your planning purposes this spring, here are answers to questions an ISU Extension crop specialist has been hearing from farmers who are concerned about seed-attacking insects. Rod Swoboda

Published on: Apr 13, 2004

Seedcorn maggots are occasional pests of both corn and soybean seeds at germination. They are more of a problem in soybean than in corn, says Brian Lang, an Iowa State University extension crop specialist at Decorah, Iowa.

Yield reduction occurs because of stand loss, and damage is more likely in cool, wet springs when the seeds are slow to germinate but the insects are still actively feeding, he says.

The greatest potential for seedcorn maggot damage exists when spring growing grass, alfalfa, and/or weeds are tilled into the soil, or fresh animal manure is applied to the field in spring. Decaying/fermenting organic matter attracts the adult flies for the females to lay eggs. When the eggs hatch, the larva may also feed on the corn and soybean seed.

If manure has been spread on the field in spring or standing forage was disked or plowed this spring, you can use a standard seed treatment like Agrox Premiere, Kernel Guard, Germate Plus, and others. Or you can also use the newer products like Poncho 250, Gaucho and Cruiser which should provide protection.

"A seed treatment is not necessary if a soil insecticide is being used for control of corn rootworms," says Lang.

Wireworm and white grub trials

"Once we get "in-season", ISU Extension will be looking for replant fields (or hot spots) for wireworms and true white grubs," says Lang. "If you find a problem with these insects and need to replant, we would like to establish a small-plot study to evaluate insecticide products. The study would be organized to fit the grower's planter, field, etc."

If you have had problems with wireworms in recent years, consider using an insecticide seed treatment in that/those fields this year, advises Lang. Wireworms can live in the larval/feeding stage for up to 8 years.

Although problems are more likely to occur in corn following sod or CRP, wireworm problems are becoming more common in a corn-soybean rotation. Several planter-box seed treatments (containing lindane), including Agrox DL Plus, Germate Plus, and Kernel Guard Supreme give early season protection to corn from wireworms.

Evaluations of insecticides for wireworm control can be found in the 3/20/00 and 4/10/00 issues of ISU's ICM Newsletter:

http://www.ipm.iastate.edu/ipm/icm/2000/3-20-2000/wwp1.html

http://www.ipm.iastate.edu/ipm/icm/2000/4-10-2000/wireworms2.html

For protection from this pest, it is also possible to buy seed treated with Poncho and Cruiser for corn, and Gaucho as a Section 18 label for soybeans.