April showers have brought forth a lot of things in 2019, some of them more welcome than others. Among the less desirable, perhaps, was a sharp spike in armyworm activity in pastures in the northern half of the state.
As early as May 1, Cooperative Extension Service agents in several counties began receiving calls from producers as the pest made its annual appearance, chewing its way through one bermudagrass field in Crawford County. Over the following two weeks, the pest — alternately referred to as the “true armyworm,” and not to be confused with the “fall armyworm” — also stirred the ire of growers in Searcy, Boone, and Randolph counties, among others — all in fescue fields.
Kelly Loftin, extension entomologist for the University of Arkansas System Division of Agriculture, said the pest’s appearance isn’t unusual for this time of the year.
“It’s pretty typical, to have a spike like that in early May,” Loftin said. “They’re normally found in pastures, north of the River Valley.”
The armyworm, which takes several forms throughout the course of its brief life, primarily inflicts its damage while a caterpillar, spending about two weeks feeding on grasses before getting back to transforming to a moth.
“It’s basically an issue of forage loss,” Loftin said. “They infest the field and reduce yield. It can be quite devastating. In fescue, if the timing’s just right, the invasion can affect seed production.”
Loftin said that damage from only one generation of true armyworms is inflicted per season, unlike the fall armyworm, which can rally multiple generations to attack a crop simultaneously.
He said the unusually wet conditions this May have likely not had any effect on the true armyworm populations in the state one way or another. While Arkansas doesn’t usually see true armyworms in the sheer numbers that fall armyworms present, the treatment threshold is two to three caterpillars per square foot to justify the use of pesticides.
Luckily, the populations are likely on their way out, Loftin said.
“It’s mostly passed now, or will be, shortly,” he said.