Fall Armyworm Populations Much Reduced Compared to 2021

Last year about this time, entomologists, growers, homeowners, and media outlets from around our region (Kentucky to Ontario and beyond) were reporting surprising infestations of fall armyworm in grass hay and alfalfa fields, fields planted with cover crops, and even residential lawns, among other sites. The outbreak of fall armyworm was unprecedented and caused a lot of people angst and/or crop losses.

This year, fortunately, the situation seems to be very different. Penn State's PestWatch trapping network has been finding very few moths, indicating that fall armyworm populations in Pennsylvania are low and unlikely to produce populations of caterpillars that will cause widespread damage. Nevertheless, fall armyworm is a perennial visitor to Pennsylvania and can cause damage every year if it is locally abundant. Just recently, in fact, a crop consultant in Union County found non-Bt corn infested with fall armyworm (Figure 1). So, obviously, the risk is not zero. The solution to the risk posed by fall armyworm, and pests generally, is to scout field regularly looking for damage and applying a rescue treatment if necessary. For "normal" populations of fall armyworm, I would prioritize scouting for damage in non-Bt corn, sorghum-sudangrass, and grass hay fields. I would also keep an eye on extension reports, like this one, to learn if the risk might be higher than usual. For more detail on fall armyworm biology and life cycle, see our factsheet on fall armyworm in corn.