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Published September 12, 2011, 05:23 AM

Nice fall would boost grasshopper numbers next year

A warm, dry fall in Montana, western North Dakota and western South Dakota would help farmers finish their harvest.

By: Jonathan Knutson, Agweek

A warm, dry fall in Montana, western North Dakota and western South Dakota would help farmers finish their harvest.

But dry conditions also could set the stage for major problems with grasshoppers next year, experts say.

“Next year could be bad again,” says Gary Adams, the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service’s state plant health director in Montana.

The good news is that grasshoppers haven’t been as bad in the region this year as once feared.

Going into 2011, grasshoppers were judged as posing a potential hazard on roughly 59 million acres of U.S. rangeland, according to a 2010 federal survey of adult grasshopper populations.

An area with 15 or more grasshoppers per square yard, or roughly 72,000 grasshoppers per acre, is judged as being particularly worrisome, particularly in years when vegetation is relatively scarce.

A grasshopper can eat about half its body weight in vegetation each day. Thirty pounds of grasshoppers can eat roughly as much grass as one 600-pound steer.

Montana a hot spot

Most of the potentially troublesome 59 million acres were identified in Montana, Nebraska and Texas, with Montana accounting for 22 million of the 59 million acres. Most of Montana’s acres at greatest risk were in the eastern half of the state, according to the survey.

Grasshoppers were a major concern in Montana in 2010, and experts feared the insects could be a big problem again this year. But heavy spring rains killed some grasshoppers or delayed their hatch, reducing the threat, Adams says,

Still, “There are a lot of grasshoppers,” he says.

The recently released USDA-APHIS 2011 survey of adult grasshoppers in Montana found that grasshopper populations of 15 or more per square yard are common again this year in the eastern half of the state.

Vegetation is unusually abundant this fall, which complicates efforts to assess how much damage grasshoppers might be doing, Adams says.

Recent hot, dry weather in the state has favored grasshopper development, says Kevin Wanner, Montana State University entomologist.

“The warmer weather will likely increase the number and size of egg-laying female grasshoppers, meaning the grasshopper outbreak will continue next year,” he says.

“A hot dry spring next year in 2012 could make the outbreak more dangerous,” he says.

That creates concern for fall-planted winter wheat that will be emerging and susceptible next spring, he says.

Hoppers in ND, SD

Most of North Dakota was judged to be free of risk from grasshoppers this year, although pockets of the insects were predicted for parts of south-central and southwestern North Dakota.

Those early predictions generally have come to pass, says Janet Knodel, North Dakota State Extension Service entomologist.

She’s heard only a few reports of grasshopper problems in the state, mostly in the Dickinson, N.D., area.

She notes, however, that grasshoppers could become a much bigger concern next year. Vegetation in much of the state is unusually green this fall, giving grasshoppers more to eat, and warm, dry weather ahead would extend the insects’ egg-laying season, she says.

Grasshoppers posed a potential hazard in the western half of South Dakota, through relatively little of the state was judged to face the threat of 15 or more grasshoppers per square yard, according to the 2010 APHIS survey.

Wet conditions this spring helped hold down hoppers, although they were plentiful again, says Maurice Lemke, extension agent in South Dakota’s Ziebach County, which was hit hard by grasshoppers in both 2010 and 2011.

Farmers in his county would benefit from warm, dry weather through the end of September to help harvest, he says.

Ideally, that warm, dry weather would be followed by a killing frost, which would work against grasshoppers, he says.

Last year, South Dakota had the greatest number of grasshoppers in the recent memory, says Bruce Helbig, APHIS state plant health director in South Dakota.

But abundant moisture this spring delayed the hatch, holding down problems this summer, he says.

Even so, conditions this fall will influence grasshopper numbers next year, he says.

A widespread early frost this fall would kill many grasshoppers, reducing the threat in 2012, experts say.

Grasshoppers have a long history of doing damage in the Upper Midwest, so it’s important to maintain strategies for controlling them, Helbig says.

Information: www.sidney.ars.usda.

gov/grasshopper.

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