Western bean cutworm, a destructive insect that can cause severe yield loss in cornfields, spread this past growing season into the northern half of Illinois and many counties in Wisconsin. Before 2005, the insect was confirmed in Iowa, southern Minnesota, northern Missouri, Colorado, South Dakota, Nebraska, western Kansas and the panhandles of Texas and Oklahoma. This leaves many growers wondering about WBC control measures for 2006.
Traps set by Extension agents from the University of Illinois and the University of Wisconsin, as well as Pioneer Hi-Bred International, Inc., agronomists in Illinois, confirm the spread of this insect into these states
Young WBC larvae feed on tassels and silks, but eventually tunnel through the silk channel to reach the developing kernels. Direct yield loss occurs as the larvae consume all or parts of developing kernels. Partially consumed kernels may be further attacked by ear molds or secondary insect feeders that enter the ear through the WBC feeding channel.
"When fields average several WBC larvae per plant, yield losses may be as high as 30% to 40%," says Paula Davis, senior marketing manager for insect and disease control traits at Pioneer.
Although it is unclear why the WBC has expanded its area so quickly, several factors may be involved including mild winters, reduced use of foliar insecticides and increased use of no-till systems