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Entomologist predicts some farmers could lose three percent or more in yield per ear

Agriculture.com Staff 09/18/2006 @ 8:28am

New field data suggests corn farmers can see more crop damage this year from a pest that they have little experience fighting.

Insect pheromone traps placed by universities and other collaborators, such as Pioneer Hi-Bred International,Inc., in corn fields throughout the Midwest to help track western bean cutworms are showing the pest has moved further east than ever. Once known mainly as a western U.S. dry bean pest, in recent years it has moved to corn fields and steadily expanded its range eastward into the heart of the Corn Belt.

The traps show that western bean cutworm moths have reached the northern half of Illinois, northwestern Indiana, southern Wisconsin and western Ohio. Heaviest flights were reported across Nebraska, Iowa and northwestern Illinois.

"For corn growers in Iowa, the western bean cutworm has replaced the European corn borer as the number one pest to cause corn ear damage," says Marlin Rice, professor of entomology at Iowa State University. "In fields with non-Bt corn hybrids, I've seen as much as 70% to 90% ear infestation. I would estimate an average of two- to three-percent yield loss per ear in those fields. In some fields, it may be higher than that."

Kevin Steffey, extension specialist and professor of agricultural entomology at the University of Illinois, said that after a somewhat "lonely" discovery in Warren County, Illinois in 2004, traps have documented the rapid spread eastward and southward of the western bean cutworm through Illinois.

"As of Aug. 4, moths had been captured as far south as St. Clair and Washington counties in Illinois and as far east as western Ohio," says Steffey. "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."

Iowa State University, with the cooperation of other land grant universities, has tracked the emergence patterns of western bean cutworm since 2002. Click here for data gathered this year and other information on the pest.

Both entomologists recommend farmers watch closely for signs of damage from the western bean cutworm as they harvest the crop. Though there isn't much that can be done for the 2006 crop, growers who have the pest in their area have options for controlling the pest next year.

"Some producers will want to consider planting a corn hybrid with Herculex I or Herculex XTRA that will control western bean cutworm, whereas others may decide to address management next year by regular scouting and application of an insecticide if needed," Steffey says.

Regardless of the management plan, it is very important to not overreact, said Steffey. Growers should sharpen their insect identification skills and make sure they have accurately identified western bean cutworm before selecting the best management solution.

Controlling western bean cutworm with insecticides has proven difficult. Insecticide timing is critical to achieve acceptable control. Once larvae enter the ear for feeding, it is almost impossible to reach them with insecticide sprays.

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