Indiana Ag Connection - Western Bean Cutworm Season Beginning in Indiana

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Western Bean Cutworm Season Beginning in Indiana
Indiana Ag Connection - 07/07/2009

Crop producers should start scouting for signs of western bean cutworms in about a week, according to a Purdue University Extension specialist, after the first signs of the corn pest recently were 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 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.

Indiana was introduced to the western bean cutworm 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 them to be significantly lower here, though it will be worst where the insects were observed last year.

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 to 8 percent of plants infested should receive an aerial insecticide, he said. He said Cry1F Bt corn seed has also 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.