Integrated Crop Management

Western bean cutworm added to Herculex registration

On August 22, 2003, the Environmental Protection Agency amended the registration of Herculex™ I Insect Protection to include western bean cutworm. Herculex is a genetically modified protein (Cry1F) that has been inserted into corn to provide in-plant protection. It was developed in collaboration between Dow AgroSciences, Mycogen Seeds, and Pioneer Hi-Bred International, Inc. In addition to western bean cutworm, Herculex I provides protection against first- and second-generation European corn borer, black cutworm, and intermediate suppression of corn earworm.

The western bean cutworm is a midseason corn pest that can cause extensive damage to the corn ear. It is not uncommon to find several larvae in an ear destroying the developing kernels because the larvae are not cannibalistic, like corn earworms. Additionally, damaged ears often are invaded by molds that further reduce grain quality.

Western bean cutworm feeding on corn ear.

The western bean cutworm has become a more significant pest of corn in Iowa during the last four years. Damage can be substantial in commercial corn fields, particularly in northwestern Iowa, although damage has been found near Ames and Waterloo. Information on where moths were trapped in 2003 can be found at [2]. This information, however, should not be interpreted to imply that these locations will have economic damage next year or that locations without traps did not suffer yield loss from western bean cutworms in 2003.

Several insecticides are labeled for this insect, but like any pest that feeds inside the ear, proper field scouting and timing of an insecticide are critical to the successful control of this insect. Herculex will offer producers an alternative to controlling western bean cutworms in 2004. Corn ears that I observed in several test plots in northwestern Iowa in 2002 showed that Herculex provided very good protection against western bean cutworms. I would not categorize it as total protection, but the level of control was impressive and superior to YieldGard hybrids, which do not offer any control of western bean cutworms.

This article originally appeared on page 151 of the IC-490(21) -- September 15, 2003 issue.

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