Armyworms turn up in central cornfields in Stearns County

Published 9:05 am Friday, July 26, 2013

AVON — Armyworms are being blamed for damaging a number of central Minnesota cornfields in recent days, though experts aren’t sure about the extent and severity of the infestation.

The corn in Glen Ritter’s 20-acre field near Avon in Stearns County should be shoulder-high by now. Instead, he said, the field that helps supply his 70-head dairy operation is probably a total loss.

For hundreds of yards in every direction one could see one green shoot jutting out of the soil where there should have been a cornstalk. Most of the leaves were gone. The few that remained often held the object of his disgust: telltale armyworms about an inch-and-a-half long.

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“This pretty much says it all when you drive right through your corn and you don’t even care,” Ritter said.

Pests that Randy Smude said he thinks were armyworms ruined about 17 of the 150 acres he’s planted near Pine Center in Crow Wing County. He told the Brainerd Dispatch the pests had eaten stalks right down to the ground in some places.

“It looks like cactuses out there. I don’t know what to do. I’ve never had it before” he said.

Bruce Potter, an integrated pest management specialist with the University of Minnesota Southwest Research and Outreach Center in Lamberton, has heard limited information from observers that there’s a large arc of infestation from southeast Minnesota, through east-central and central Minnesota into North Dakota. But he said the geographic scope could be larger and he doesn’t know how severe the infestation might be.

Geir Friisoe, director of the plant protection division at the Minnesota Department of Agriculture, said he was a little surprised by the reports because it’s unusual to see armyworms this far north, but they sometimes blow up from southern states.

“It can be quite devastating when they show up in large numbers, but it is a relatively unusual thing to happen in Minnesota,” he said.

True armyworms are different from tent caterpillars, which feed on broadleaf trees and shrubs and are sometimes called armyworms.

Friisoe said effective insecticides are available to treat infestations, but growers need to be vigilant because the pests can do a lot of damage quickly.

“They’ll strip all the leaves off. It’ll look like as big hailstorm came through,” he said.

Ritter engaged Centra Sota Cooperative in Albany to spray the rest of the 200 acres he had planted. He said the cost would amount to a couple thousand dollars.

“But what are you going to do?” Ritter said. “If you don’t spray, you could wind up with nothing.”

Jesse Breddeck, who drove the sprayer, said this is the first time in his four years with Centra Sota that he’s sprayed for army worms.

“It’s been a long time since we had any fun with armyworms — probably since the 1990s when there were some pretty serious infestations up in Rice,” said Rick Gilbertson, a crop consultant based in Sauk Rapids. “Fortunately, the only people who have to really worry about them are the ones who have grassy weeds in or near their cornfields. That’s the key. Without that, the moths that lay the eggs that become the armyworms won’t go there.”

Gilbertson said this batch of armyworms likely came from a large moth flight from southeastern Minnesota three weeks ago. He’s had reports from south of St. Cloud and near Pierz, Sauk Centre, even Fargo, N.D. But he said he expected the war would be over in a week.

“It’s a small percentage of our overall farmers who will have this problem,” Gilbertson said. “And the insecticide is very effective. But they’re called army worms for a reason. They can devour 10 to 20 acres in a day. So catching them early is essential.”