Western Bean Cutworm Damage - The western bean cutworm, a new pest in parts of the Corn Belt, can inflict severe damage on the corn plant ear.  Moth trappings show that the pest is traveling eastward in recent years across the Corn Belt.  According to university entomologists, the western bean cutworm has replaced the European corn borer as the number one pest to cause ear damage to corn.

Corn Damage from Western Bean Cutworm - Young western bean cutworm larvae feed on tassels and silks, but eventually tunnel through the silk channel to reach the developing kernels. Direct yield loss occurs as larvae consume all or parts of developing kernels. Partially consumed kernels may be attacked further by ear molds or secondary insect feeders that enter the ear through the western bean cutworm feeding channel.

Western Bean Cutworm Adult Moths - Adult western bean cutworm moths emerge in mid- to late July, mate and begin laying eggs immediately. The moths lay eggs in masses of five to 200. Eggs will turn purple by the fifth day of development and hatch as larvae one or two days later. These moths have been seen moving eastward across the Corn Belt.

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," said 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 percent ear infestation," said Rice. "I would estimate an average of 2 to 3 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, Ill., 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," noted 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."

ISU, with the cooperation of other land grant universities, has tracked the emergence patterns of western bean cutworm since 2002. Data gathered this year and other information on the pest can be found at http://www.ent.iastate.edu/trap/westernbeancutworm .

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," said Steffey.

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.

"Herculex® I is the best tool available today for the management of western bean cutworm," said Rice. "I've recently looked at ears from fields planted with hybrids with the Herculex® I trait having no significant damage from western bean cutworm."

Unlike competitive insect resistant traits for corn, Herculex® I controls the western bean cutworm along with the European corn borer and several other pests. Herculex® XTRA contains both the Herculex® I trait and the Herculex® RW trait for corn rootworm control.

The Herculex® family of corn traits was developed by DuPont subsidiary Pioneer Hi-Bred International, Inc., and Dow AgroSciences. Hybrids with the trait are available from Pioneer.

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 technology by Dow AgroSciences and Pioneer Hi-Bred. Herculex® and the HX logos are registered trademarks of Dow AgroSciences LLC.

For more detailed information on western bean cutworm, see the Crop Insights, "Managing Western Bean Cutworm," from Pioneer Hi-Bred International, Inc.

Western Bean Cutworm Can Severely Damage Corn

Once known mainly as a pest of dry beans in the western United States, western bean cutworm has adapted to corn and expanded its range further east.

Adult western bean cutworm moths emerge in mid- to late-July, mate and begin laying eggs immediately. The moths lay eggs in masses of five to 200. Eggs will turn purple by the fifth day of development and hatch as larvae one or two days later.

Young cutworm larvae feed on tassels and silks, but eventually tunnel through the silk channel to reach the developing kernels. Direct yield loss occurs as larvae consume all or parts of developing kernels. Partially consumed kernels may be attacked further by ear molds or secondary insect feeders that enter the ear through the WBC feeding channel.

Growers may be wondering why this insect continues to spread and increase in population. Paula Davis, senior marketing manager for insect and disease control traits at Pioneer Hi-Bred International, Inc., Des Moines, Iowa, attributed several factors to the proliferation of this insect.

"A combination of mild winters, reduced use of foliar insecticides and increased use of no-till systems could factor in to the spread of this insect," said Davis.