Moths on the Move

Large Populations of True Armyworm Moths Heading North Early

Emily Unglesbee
By  Emily Unglesbee , DTN Staff Reporter
Connect with Emily:
True armyworm moths are moving north in large numbers after a mild winter encouraged their overwintering survival in the Midsouth and even Midwest. (Photo courtesy Luis Miguel Bugallo Sanchez)

ROCKVILLE, Md. (DTN) -- An army is moving north, and it's headed for your fields.

Large populations of true armyworm moths gathered forces earlier than ever this year in the Midsouth, thanks to a mild winter. Now they're on the move.

Entomologists in Midwestern states like Illinois, Indiana and Ohio are raising alarms as giant moth flights sweep through their insect traps nearly a month ahead of normal. The moths will lay eggs that will hatch in a few weeks with larvae hungry for grain crops like corn, wheat or barley.

In the Midsouth where corn planting is well underway, entomologists are urging growers to scout now for hatched armyworm larvae.

"Usually the moths emerge around April here," University of Kentucky entomologist Raul Villanueva told DTN. "But this year they came out extremely early at the end of February and the beginning of March, so they are already there, in the fields."

Midwestern growers should plan on scouting in two to three weeks (early to mid-May) based on high moth counts now, according to Purdue University entomologists Christian Krupke and John Obermeyer.

(Don't confuse true armyworms with fall armyworms, which emerge as crop pests later in the summer.)


True armyworm moths usually swoop up from the South into the Corn Belt in the spring each year. However, given the unusually warm winter, many likely overwintered as far north as Indiana, Krupke and Obermeyer noted in a university pest update.

The moths prefer to lay eggs in grassy vegetation, so they will target fields with wheat, grass hay or grass cover crops, the entomologists said.

The best way to protect future corn fields is to make sure any vegetation is burned down at least two weeks before planting. Of course, Mother Nature may not permit this.

"With this spring's wet weather, spraying of cover crops has been delayed, and that will likely often be the case," Krupke and Obermeyer wrote. "So we're aware that the two- to three-week window won't often be possible. But it is worth mentioning, because armyworm larvae without a 'green bridge' between food sources will quickly starve."


Certain Bt-traited corn hybrids list true armyworm among the pests they control on their label. (See which Bt proteins are in your corn hybrids with Michigan State's Handy Bt Trait Table here:….)

But don't assume you are totally protected by these Bt proteins, Krupke and Obermeyer warned.

"Don't be dependent on traited-corn, as high armyworm infestations will still cause significant damage before the Bt-proteins suppress their feeding," they wrote.

Nor will insecticide-treated seed protect a young corn seedling. Only foliar sprays can consistently kill armyworm infestations, so careful scouting will be key in the coming weeks.


For help scouting and treating for true armyworm in small grains crops, see Villanueva's website here:…. For help scouting corn, see this article from the University of Wisconsin:….

See Krupke and Obermeyer's article here:….

Emily Unglesbee can be reached at

Follow Emily Unglesbee on Twitter @Emily_Unglesbee


Emily Unglesbee