This photo shows one healthy armyworm caterpillar and three killed by a pathogen, likely a virus. Infected caterpillars are typically found head down. Viruses spread from their dying bodies to infect others in the populations.
A second generation of true armyworms could cause problems in corn and grass hayfields across Pennsylvania, New York and Ohio, says John Tooker, Penn State University entomologist.
Growers should walk fields and be on the lookout for the new generation in early July, he adds.
“This has been a widespread, destructive and generally impressive situation. Caterpillars are “marching across corn, wheat and grass hayfields. When large populations of insects develop, their diseases and other natural enemies are typically not far behind.”
Potato leafhoppers exceeded economic thresholds in alfalfa in Pennsylvania’s Centre Region and have been treated, Tooker says. He warns growers to keep sweep nets handy and watch fields. “Remember that once you see evidence of feeding damage (hopper burn on leaves), yield loss has already begun.”
Watch cornfields, too. Western corn rootworm adults are just starting to emerge, Tooker says. Conditions look quite good for the pests this spring, so growers with continuous corn acreage need to keep track of any higher-than-expected damage to roots.