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Published June 14, 2009, 12:00 AM

Black grass bug doing damage

Black grass bugs have been causing problems on Conservation Reserve Program land and pastures in Adams and Bowman counties

By: Beth Wischmeyer, The Dickinson Press

Black grass bugs have been causing problems on Conservation Reserve Program land and pastures in Adams and Bowman counties in the southwestern part of the state, North Dakota State University Extension staff say.

The problem was first presented by area producers who noticed issues with their crops last week.

“I had a producer that stopped me, showed me some pictures and wanted to know what’s going on,” said Julie Kramlich, NDSU Hettinger Research Extension Center agent. “He had little black bugs in his winter wheat field and it was turning yellow.”

Agents determined they were black grass bugs, an insect not seen often in the area.

“Typically the problem is more further west in Utah and some of the other states,” said Jan Knodel, NDSU Extension Service entomologist.

The heavy infestations in some cases have caused the black grass bugs to move into adjacent wheat and barley fields.

“Black grass bugs feed on a variety of grasses, such as crested wheat grass, brome grass, bluegrass and orchard grass, and field crops, such as wheat, barley, rye and oats,” Knodel said. “Crested wheat grass is the most preferred grass. Adult and nymphs feed by piercing and extracting the green tissue from the plants.”

The feeding causes white spots and blotches on plant foliage. Heavily infested plants can appear frosted. Small black spots of excrement covering the plants can also be seen.

The bugs feed for four to five weeks until they finish maturing. They will then lay eggs which will hatch next spring, Kramlich said.

“Wheat can sustain quite a bit of black grass bug feeding injury without significant yield losses unless the flag leaf is severely damaged or the wheat is stressed by moisture, fertility or other pests,” Knodel said.

Insecticide control typically is not recommended for CRP land, rangeland or pastures unless the grass is grown for seed production. No economic threshold has been developed for black grass bugs. However, populations that exceed 1,000 bugs per square foot can kill a plant, Knodel said.

Insecticides will kill the adults and nymphs but not the eggs in the stems.

Knodel added that producers need to remember that black grass bug control with insecticides typically is not practical or economical.

Mowing, haying and grazing in late fall or early spring is recommended to reduce the number of egg-laying sites.

“One well-timed insecticide application targeting the nymphs and adult females prior to laying egg easily can control black grass bug populations,” Knodel says.

For more information on insecticides that can be affective, contact Knodel at 701-231-7581.

“We don’t know how the pastures will come back,” Kramlich said. “We’ll have to see how things turn out.”

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