URBANA, Ill. — Research conducted by universities and industry researchers shows the western bean cutworm is continuing its eastward advance.

Known primarily as a western U.S. dry bean pest, the voracious cutworms have made their presence known in the heart of the Corn Belt for the past few years. Studies conducted by entomologists from the University of Illinois (UOI) and other collaborators have helped trace the cutworm’s eastern migration.

“As of Aug. 4, moths had been captured as far south as far as St. Clair and Washington counties in Illinois and as far east as western Ohio,” said Kevin Steffey, a UOI entomologist. “The number of moths captured in traps has been particularly large in Illinois in northwestern counties: Jo Daviess, Stephenson, Winnebago, Carroll, Ogle, Whiteside and Bureau.”

Entomologists began setting traps for the cutworms in 2004, after one was identified in Warren County.

Marlin Rice, professor of entomology at Iowa State University (ISU), said the western bean cutworm has replaced the European corn borer as the No. 1 pest regarding corn ear damage.

“In fields with non-Bt corn hybrids, I’ve seen as much as 70-90 percent ear infestation,” Rice said. “I would estimate an average of 2-3 percent yield loss per ear in those fields. In some fields, it may be higher than that.”

Adult western bean cutworm moths lay their eggs in late July in masses of 5-200. Eggs will hatch as larvae within 5-7 days. The larvae feed on tassels and silks, and tunnel through the silk channel to feed on developing kernels.

Steffey said that since corn is already being harvested across the Midwest, producers will want to begin thinking about how to address western bean cutworm management next season.

“Growers should sharpen their insect identification skills and make sure they have accurately identified western bean cutworm before selecting the best management solution,” he said.

Steffey identified insecticides registered in Illinois for control of western bean cutworms in corn. They include Asana XL, Baythroid 2, Capture 2EC, Intrepid, Lorsban 4E, Mustang Max, Penncap-M, Pounce 3.2EC, Proaxis, Sevin XLR Plus, Tracer 4SC, and Warrior. The list contains seven pyrethroids (Asana, Baythroid, Capture, Mustang, Pounce, Proaxis, Warrior), two organophosphates (Lorsban, Penncap-M), one carbonate (Sevin), one molting hormone agonist (Intrepid) and one naturalyte (Tracer).

“The two products least toxic to mammals are Intrepid and Tracer,” Steffey said. “Generally, pyrethroids are considered less toxic than organophosphates and carbonates, and pyrethroids are very effective against most caterpillars, including the western bean cutworm.”

ISU’s Rice said Herculex could be the best tool available for the management of western bean cutworm.

“I’ve recently looked at ears from fields planted with hybrids with the Herculex I trait having no significant damage from western bean cutworm,” Rice stated.

Paula Davis, senior marketing manager for insect and disease control traits at Pioneer Hi-Bred, attributed several factors to the migration of the pest.

“A combination of mild winters, reduced use of foliar insecticides and increased use of no-till systems could factor into the spread of this insect,” said Davis, whose company is participating in the research project.

This farm news was published in the Sept. 27, 2006 issue of Farm World, serving Indiana, Ohio, Illinois, Kentucky, Michigan and Tennessee.