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Western bean cutworm season beginning in Indiana

WEST LAFAYETTE, Ind. — Crop producers should start scouting for signs of western bean cutworms this week, according to a Purdue University Extension specialist, after the first signs of the corn pest were recently found in northwestern Indiana.

“Typically at the end of June we start catching our first moths, and that’s what’s happened this year,” said John Obermeyer, Purdue Extension integrated pest management specialist.

Western bean cutworm eggs look like dozens of tiny pearls on the upper surface of the top leaves of a corn plant. (Photo courtesy of John Obermeyer)

Western bean cutworm eggs look like dozens of tiny pearls on the upper surface of the top leaves of a corn plant. (Photo courtesy of John Obermeyer)

Western bean cutworm is a pest that can cause damage to ears of corn. A cluster of about 50 to 100 small, white, pearl-like eggs are laid on the upper surfaces of the top leaves of a plant. They will turn a deep purple just before hatching, Obermeyer said.

Once hatched, larvae get quickly into the corn whorl and eat until ears are formed. Once in an ear, they will eat before cutting out of the ear and dropping to the ground to winter, becoming moths the following summer. Molds often form where the worms have eaten.

Western bean cutworm first showed up in Indiana about three years ago. But in areas that have been dealing with the pest for decades, Obermeyer said, yield losses could be as high as 20 percent, although that is unusual. He expected the losses to be significantly lower in the state, though it will be worst where the insects were observed last year.

Western bean cutworms can cause extensive damage to an ear of corn once inside. Once gone, the ears are also susceptible to mold. (Photo courtesy of John Obermeyer)

Western bean cutworms can cause extensive damage to an ear of corn once inside. Once gone, the ears are also susceptible to mold. (Photo courtesy of John Obermeyer)

Western bean cutworms like sandier soils with continuous corn rotations. They are attracted to fields that soon will or are actively pollinating.

Obermeyer said producers should check 20 consecutive plants for egg masses. Anything higher than 5 percent to 8 percent of plants infested should receive an aerial insecticide, he said. He said Cry1F Bt corn seed also has been effective in controlling western bean cutworm.

“Once we start seeing moths, which we have in the northwestern counties, we know the eggs aren’t too far behind,” Obermeyer said. “Egg scouting is the only chance we have of catching them before they get into an ear.”

Obermeyer said the western bean cutworm is most likely to be seen in northwestern Indiana counties, and as far south as Benton County. One moth was seen on the eastern border of Indiana in Jay County already this year.

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One Response to “Western bean cutworm season beginning in Indiana”

  1. Galen Frantz says:

    I recently read an article describing how this pest is expanding its range eastward. My company consults with sweet corn growers throughout Florida and in south Georgia. Do you have any information about the potential southern extent of this pest’s range? Are you aware of any reports of WBCW in the Southeast?

    I look forward to hearing from you.

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