Production Blog

Seasonal Cadence: Armyworms Are Marching Again

Pamela Smith
By  Pamela Smith , Crops Technology Editor
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A sweep net filled with fall armyworms is never a good thing. This year is a particularly difficult year for the pest in the Southern states, and the watch is on farther north. (Photo by Gus Lorenz, University of Arkansas)

Armyworms remain one of the enduring memories of my youth. Like the big fish that got away, one summer an armyworm outbreak decimated the best soft red winter wheat crop we "ever" had on our central Illinois farm.

These armyworms didn't infest, they invaded. I watched with my father as they marched down the dirt lane that bordered our wheat field. The road was solid with the army-green caterpillars, and I kid you not, you could hear, as well as see, them moving to their next meal.

"Left, left, left ... I left my wife and 49 kids with nothing but wheat stems ... left."

Right ... This past week, my email inbox started to overrun with warnings about fall armyworms marching through Southern crops in Texas, Alabama, Arkansas and Mississippi. Words like "epic" and "not since the 1970s" are being used to describe the 2021 outbreak.

The armyworm nightmare of my youth was likely the true armyworm, rather than the fall armyworms now causing issues. Whatever the name, they'd not been invited to dine at our expense.

Our invasion brought the first crop-dusting plane I remember to the farm as Dad declared his own war. He was Army. I had been born in an Army hospital, but even ground pounders understand the power of strategic aerial assault. Integrated pest management (IPM) wasn't on our radar yet, and we were going to guard our homeland or go out trying.

I recall watching the spray plane dip, dive and strafe the field while the children of our tribe jumped and flailed our arms like shipwrecked fools from a safe distance. Truth be told, we did that with every plane that passed over -- perpetually in awe that our remote spot on this earth had been discovered. A plane flying back and forth ... well, that was like being allowed to simultaneously eat candy AND ice cream, before eating dinner.

These days I am no less amazed when I hear, and see, big insect events catch us off guard. Fall armyworms do not overwinter in many U.S. agricultural states but migrate northward from the Gulf Coast area with the first wave of migrants typically arriving in late June in the Midwest.

Extension educators and IPM specialists do an excellent job of monitoring and reporting moth captures and issuing orders to scout for these invaders. Fall armyworms do have natural predators, and that's important to consider in treatment decisions. Still, despite all our early warnings, these insects remain stealthy adversaries.

In a University of Arkansas news release posted in late July, Jarrod Hardke, University of Arkansas rice agronomist, explained why fall armyworms can pull a fast one.

"They have a tendency to surprise us because adults lay very large egg masses, but the earliest instar larvae eat very little. It's not until they get older and start to spread out that they consume most of the food in their life cycle.

"This is why we go from zero to TREAT seemingly overnight," Hardke said.

If that happens (and I sincerely hope it doesn't), think about marching your kids out to the field for an entomology lesson. They'll be LEFT with a lasting memory and an appreciation of what it takes to put harvested grain in the hopper.

Find several excellent news releases from the University of Arkansas communications staff on fall armyworms here: https://www.uaex.uada.edu/… and https://www.uaex.uada.edu/…. For a post regarding rice treatment considerations: https://arkansascrops.uada.edu/….

Read DTN's summary of what some states are seeing and outlook for fall armyworms here: https://www.dtnpf.com/….

Pamela Smith can be reached at pamela.smith@dtn.com

Follow her on Twitter @PamSmithDTN

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