Fall armyworms are causing damage in fields throughout the Midwest

“This is the first year of a big infestation."

Posted: Sep 14, 2021 10:01 AM

TIPPECANOE COUNTY (WLFI) — Fall Armyworms have made their way to the Midwest and have been causing damage.

Professor of Entomology at Purdue University, Christian Krupke, says we’re dealing with an infestation of fall armyworms.

“This is the first year of a big infestation,” said Krupke. “"I've never seen this in the 16 years while I've been at Purdue.”

Krupke says fall armyworms are native to Central and South America.

"It's a very uncommon occurrence,” said Krupke. “The damage they do is they have wiped out some of the fields in Indiana, and in Kentucky, and so on."

He says it’s not uncommon to find a few armyworms every year, especially in late planted corn. However he’s never seen an infestation like this one.

"This year they're making a big stir because they're feeding on a lot of crops throughout the state, particularly hay and alfalfa crops,” said Krupke. “It's worldwide and it's probably one of the biggest insect pest in the word."

There are two types of armyworms; the regular armyworms and fall armyworms.

"Both armyworms get their name because once they wipe out a field they march in a large group just like soldiers in an army,” said Krupke. “You see them crossing roads and looking for the next field."

The regular armyworms usually can be found in May and June. Krupke says they only feed on grasses, including wheat and corn, but the fall armyworms are a different story.

"Fall armyworms occur in the fall, or close to fall as we're seeing, and it feeds on a much wider range of plants like broadleaf plants and young soybeans,” said Krupke. “In addition to the alfalfa hay, it can feed on corn as well. So it has a much wider strain and it’s worldwide a much more serious pest than the true armyworm.”

Krupke says the large amount of fall armyworms we’re seeing in the Midwest is due to weather patterns.

"They fly high up in the atmosphere, in the jet stream actually, believe it or not,” said Krupke. “They get carried along those winds way up there. So the weather was favorable to bring them up from the south, carry them north, and dump them in parts of the north and in parts of the Midwest like where we are."

Krupke says they have mostly found fall armyworms in alfalfa fields, but that doesn’t mean the insects don’t cause damage to corn and soybeans.

“It can impact corn and soybeans,” said Krupke. “But at the time of year they come in Indiana most of our soybeans that are planted at a conventional time, and our corn, are past the stage where they are vulnerable.”

As the fall season gets underway, Krupke says we’re towards the end of the infestation.

However, farmers are still encouraged to check their fields.

“They need to check their fields, especially alfalfa and if they still have larvae especially small ones, they’ll need to treat them,” said Krupke. “They’ll need to apply a registered recommended insecticide.”

Krupke says there are a few things farmers need to keep in mind if they're trying to get rid of fall armyworms. 

“They’re most easy to find in the hours approaching darkness,” said Krupke. “If you really want to find them and spray them, dusk is a good time because the spray will directly encounter them.”

Krupke says it’s hard to find the fall armyworms in the day.

“You want to go out there in the fields when the insects are feeding in the evening,” said Krupke. “They hide during the day, mostly because birds will find them and eat them.”

Fall armyworms cannot tolerate the cold, which is why Krupke says the upcoming winter will determine a lot.

"You don't need to think this is an annual event," said Krupke. "But it's also more likely to happen if we have warmer weather through the winter, because the winter is our big reset button."

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