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Western Corn Rootworm Spreads Beyond Central Illinois and Indiana

A sticky trap monitoring program conducted in the beginning of August by Monsanto suggests that the western corn rootworm variant may continue to be expanding, posing a potential threat to first-year corn next season.

Monsanto distributed 28,000 Pherocon AM sticky traps in early August to growers in parts of five Central Corn Belt states — Iowa, Illinois, Indiana, Ohio and Missouri — where the rootworm variant has been expanding. Growers participating in the monitoring program, which covered more than 10 million acres, were asked to place the sticky traps in their soybean fields to determine whether the rootworm beetles are present and at what level.

The variant has adapted its reproductive practices by laying its eggs in soybean fields in order to survive field rotations between corn and soybeans. The variant eggs hatch during the spring, after the field has been rotated back to corn, resulting in larval feeding in first-year corn.

"Results from this grower data shows that the western corn rootworm beetle was trapped in almost all counties where the sticky traps were sent and placed in soybean fields by growers," says Dave Rhylander, Director of Traits for Monsanto. "This would suggest that the rootworm variant may be continuing to expand its geography, which could result in greater rootworm pressure when soybean fields are rotated back to corn in 2006. We will continue to work with university academics to validate these observations."

Because of the very dry year, deep cracks in the soil allow rootworm to lay eggs at varying depths in soil. Eggs hatch based on soil temperature, setting up a situation where deeper laid eggs hatch later in the season, explains Todd DeGooyer, YieldGuard Development Technology Manager.

DeGooyer adds that if the dry summer is followed by a cold winter with little snow, it'll prevent eggs from hatching. If there is 7-12" of snow on the ground, it won't have as great of a negative effective of keeping egg counts down.

Rhylander is recommending producers follow these steps:

• Inspect their corn fields this year and look for the presence of corn rootworm beetles. Look for lodged plants or dig corn plants and inspect the roots for feeding.
• Continue to monitor the movement of the rootworm variant in their area. Talk to other growers, local extension entomologists, retailers and seed dealers, to see if other farmers have reported lodged corn or rootworm feeding.
• Consider using technology that will control rootworm in first year corn. Monsanto launched YieldGard Plus in 2005, the first corn technology to deliver whole-season, in-plant protection against European and southwestern corn borers and effective and consistent protection against western and northern corn rootworms.
• Monitor soybeans fields in 2006 by utilizing sticky traps. Growers interested in obtaining sticky traps can call 1-866-ROOTDIG by November 15, 2005 to be put on a list to receive the traps.