Western bean cutworm (WBC), 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 percent to 40 percent," says Paula Davis, senior marketing manager for insect and disease control traits at Pioneer.

Historically, management of WBC has been limited to careful scouting and timely application of insecticides. Growers now have access to in-plant control of WBC with the Herculex® I and Herculex XTRA insect protection traits. Herculex XTRA contains both the Herculex I trait and the Herculex RW rootworm protection trait.

"Because of the labor intensive nature of scouting, the critical timing needed for insecticide applications and the possibility that multiple treatments may be necessary, insecticides may not be an economical or effective solution to the WBC problem," adds Davis.

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

Research proves efficacy of Herculex technology

Research conducted by Iowa State University in 2005 evaluated hybrids with the Herculex I technology at four locations in two Iowa counties - Hardin and Buchanan. The researchers counted the number of ears infested with WBC in hybrids with Herculex I and YieldGard® Corn Borer traits compared to their base genetics (isolines).

Counts found that 14.5 percent of the Herculex I ears were infested with WBC, whereas 78.4 percent of the YieldGard Corn Borer ears were infected and 56.5 percent of the isoline ears were infested. This research demonstrates that the Herculex I trait in corn hybrids significantly reduces risk of WBC damage.

Additional research conducted by Pioneer in 2002 and 2003 on field-sized side-by-side plots confirms those findings. In 2002, hybrids with the Herculex I trait were evaluated next to hybrids with similar base genetics at 16 locations. Hybrids with Herculex I had 4 percent ear infestation, whereas the base genetics were 25 percent infested.

In 2003, research compared Herculex I with YieldGard Corn Borer. The study found only 5 percent of the Herculex I ears were infested, while hybrids with the YieldGard Corn Borer gene were 37 percent infested.

Research conducted by Pioneer in 2004 evaluated whether hybrids with Herculex I reduced mold levels compared to their non-Bt counterparts in areas with heavy western bean cutworm infestation. Researchers sampled 10 random ears from hybrids with the Herculex I trait and a non-Bt and/or YieldGard Corn Borer hybrid at each of the six locations.

"Hybrids with the Herculex I trait greatly reduced the occurrence of WBC feeding and mold," says Davis. "In contrast, hybrids with the YieldGard Corn Borer trait and conventional hybrids had similar levels of feeding and mold."

As a result of these and other studies, Pioneer researchers confirm that hybrids with the Herculex I or Herculex XTRA trait offer very good protection against WBC feeding.

In addition to guarding against western bean cutworm, the Herculex I gene protects the corn plant against European and southwestern corn borer, black cutworm, fall armyworm, corn earworm, sugarcane borer, southern cornstalk borer and lesser cornstalk borer. Herculex XTRA protects against western, northern and Mexican corn rootworms. Herculex XTRA guards against a broader range of above- and below-ground insects in corn than any other in-seed product on the market.

Pioneer Hi-Bred International, Inc., a subsidiary of DuPont, is the world's leading source of customized solutions for farmers, livestock producers and grain and oilseed processors. With headquarters in Des Moines, Iowa, Pioneer provides access to advanced plant genetics, crop protection solutions and quality crop systems to customers in nearly 70 countries. DuPont is a science company. Founded in 1802, DuPont puts science to work by creating sustainable solutions essential to a better, safer, healthier life for people everywhere. Operating in more than 70 countries, DuPont offers a wide range of innovative products and services for markets including agriculture, nutrition, electronics, communications, safety and protection, home and construction, transportation and apparel.

® Herculex Insect Protection, Herculex XTRA Insect Protection and Herculex RW Rootworm Protection technologies by Dow AgroSciences and Pioneer Hi-Bred. Herculex and the HX logo are registered trademarks of Dow AgroSciences LLC.
® YieldGard and the YieldGard Corn Borer design are registered trademarks used under license from Monsanto Company.