Friday, March 4, 2011

Indiana's Corn Crop Susceptible to Western Bean Cutworm

Indiana and other corn farmers who thought that a new insect threat would be slowed by this winter's freezing temperatures may be disappointed, says Christian Krupke, a Purdue University Extension entomologist.

The western bean cutworm (WBC) is likely to emerge from winter in numbers capable of exacting a toll on Indiana's corn crop this summer, says Krupke.

"A question I've gotten a lot from farmers is, with the colder-than-average winter will we have a lot of mortality of the overwintering larvae?" Krupke says. "The answer is probably not. That's not because of the temperature of the air; it's more because we've had so much snow and relatively few days without snow, especially in those northwestern counties where overwintering western bean cutworm caterpillars are located."

Snow cover insulates fields and "keeps the temperature in the soil higher than it would be if the soil were bare, which actually helps the larvae survive," he says.

Fortunately, timely scouting of fields, insecticide treatments and some biotech (Bt) corn varieties have proved successful in controlling the bug.

WBC caterpillars feed on pollen and, if not controlled, the corn ear itself. That process begins after the female moths lay eggs on corn leaves about a week before corn reaches the pollination stage.

The insect was first detected in Indiana in 2006 after migrating from western Corn Belt states. Crop damage reached a peak this past year, with the most severe cases occurring in northwestern Indiana counties. WBC is most common in continuous corn and corn grown in sandy soils and no-till cropping systems.

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