Armyworms Attack Midwest, Entomologists and Farmers Say Fields Wiped Out in Hours

Fields wiped out in a matter of hours. Pests marching from grasses into farm fields and pastures. It's an armyworm infestation so intense, the pest problem is unlike anything farmers and entomologists in Ohio have ever seen.

While the late-season pest showed up early in Arkansas fields, it then moved en masse into the Buckeye State. Ohio farmers battled the pest starting in August, with the pest marching fiercely through fields, causing widespread damage.

Curtis Young, an agricultural Extension educator for Van Wert County, Ohio, and entomologist by trade, says the pest had blanketed the entire state by the end of August and beginning of September.

“(Arkansas) just happened to have a huge emergence of adults when a weather front came through that sucked them up into the jet stream and deposited them here in the northern states. So, Indiana, Illinois, Ohio, etc. all got a good dose of them from a weather front,” says Young.

This was the mower header after mowing at night, the head was clean till the sun went down! pic.twitter.com/UPfvn9Iq7w — Nick Elchinger (@NickElchinger) August 31, 2021

He says while the alfalfas seems to be the biggest victim to armyworms in Ohio this year, though they are also taking over cover crops, turf grass, sorghum and all forages.

“The moth actually has upwards of 300 different types of plants that it will feed on and thrive on. And it's partially how lush the growth is,” says Young. “With alfalfa that is cut on a regular basis, it has more lush growth more frequently throughout the entire growing season. So, it makes it much more vulnerable to the choices of the fall armyworm.”

Problem Popped Up Suddenly 

Young has been in Extension for 29 years, and he says the armyworms ravaging Ohio fields is a first.

“We weren't aware that we were supposed to be scouting for them this year, and what really set it off was suddenly the caterpillars got large enough that they were stripping the foliage off of all kinds of plants in 24 to 48 hours. And so it was a shock to the system when we finally realized that they were here in the numbers that they are,” adds Young.  “I was shocked at the number of moths that were captured in the first week that I had the traps out, literally 200-plus moths in a week's time, which is tremendously exceptional."

“We've never seen the fall armyworm really much at all before here in the fall,” says Nick Elchinger, a farmer in Deshler, Ohio. “That's what's throwing everybody kind of for a loop.”

The new enemy in Ohio fields is a battle posing a steep learning curve. Before farmers and agronomists even knew to scout, the armyworms had already latched on to fields across the state, with some farmers reporting widespread damage in just a matter of hours, with fields of alfalfa and turf turning brown overnight.

“There's about a 10- to 15-foot swath in the back field that was starting to get eaten up pretty bad, and then within eight to 10 hours, the armyworms had completely gone over this whole field. So, they move very fast when they're thick,” says Elchinger.

Devastation Within Hours 

A scouting trip Elchinger made across the 20-acre field on Friday showed no signs of feeding. By Sunday, the field was gone.

Young says scouting for the insect can be difficult. While you may not notice feeding in the beginning, armyworms can still be lurking in fields, hanging on to foliage at an angle that can be spotted by scouting from above. That was the situation in Ohio at the onset of the armyworm infestation.

PLEASE go check your hayfields and pastures for fall armyworms, and please tell others you know to go check as well. I've had them reported in all TEN of the counties I cover here in EC Iowa! #ISUCrops https://t.co/ki8sgC2L66 #ISUCrops pic.twitter.com/SULIhyGAIq — Rebecca Vittetoe (@rkvittetoe) September 15, 2021

“Once it was identified and we realized that it was the fall armyworm, then we certainly had to look into what options there were for managing it, in terms of registered insecticides for the different crops," Young says. "And then it was a matter of seeing what the availability of those products were at this time of the year.”

In Ohio, farmers and agronomists say by the time the pest started stripping vegetation and leaves off plants, the armyworms were so large, a heavy dose of insecticide was needed to actually kill the worms.

“Unfortunately, since these caterpillars are treated on a regular basis down South, there's already a fair amount of resistance in the genetics of these populations,” Young says. “Our standard insecticides, a lot of our synthetic pyrethroids, were only 40% to maybe 60% effective against these older caterpillars at best. “

Second Wave

While Ohio farmers learn to combat the pest, entomologists like Young fear another outbreak this fall is possible.

“More than likely, they're not going to stop their development because they're not adapted to the northern climates. So, they will just keep on going through their normal growth and development. And unfortunately, we could potentially see another flush of adult moths here before the end of September, which would start the cycle over again with egg laying and additional larvae.”

pic.twitter.com/FhqGEWVaO0 — Nick Elchinger (@NickElchinger) August 30, 2021

Lingering Problems For 2021?

What’s the best way to stop armyworms in their tracks? Mother Nature and a hard freeze. Young says that will kill development of a pest that doesn’t over-winter in northern climates like Ohio.

“We need to watch our late-season crops such as our cover crops, our winter wheat and our forage crops until we finally get a good hard freeze that will stop the population that is here now,” he says. “

An issue Mother Nature introduced is one only Mother Nature will be able to wipe out.

“This pest is a very, very steep learning curve for everybody here in the North,” says Young. “Unlike down South where they deal with it every year and know what to look for and when to look for it, this one was a shocker to our system. It just came out of the blue, and now we'll be prepared to look for it in the future. However, this may be a once in a lifetime event for us, or at least hopefully, it'll be a once in a lifetime event.”