By Blake Jackson
In late August, many Pennsylvanians were alarmed to find their once-healthy lawns and fields suddenly destroyed. Farmers, homeowners, and landscapers alike were left wondering: “What happened overnight?” The culprit fall armyworms had made an unexpected appearance.
Fall armyworms are caterpillars that aggressively feed on over 70 plant species, including grasses, corn, soybeans, and alfalfa. Native to the Americas, these pests are the larvae of the tropical moth Spodoptera frugiperda, which cannot survive Pennsylvania’s winters. In the U.S., they only overwinter in regions like South Florida and South Texas.
So how did they get here? Each generation of moths migrates northward during the growing season. In 2021, strong storm systems likely carried the moths hundreds of miles north into Pennsylvania. Once here, they laid eggs on plants and structures.
These eggs hatch within a few days into caterpillars that feed, grow rapidly, and travel in large groups, leaving damaged lawns and crops in their wake.
Fall armyworms go through seven instars, increasing in size and appetite with each stage. Mature caterpillars, about 1½ inches long, then burrow into the soil to pupate. After one to four weeks, new moths emerge and continue the cycle though Pennsylvania’s cooler weather usually slows or stops additional generations.
If your lawn has been affected, don’t panic. Healthy turf typically recovers. Raise mowing heights, irrigate properly, and apply a fall fertilizer with slow-release nitrogen to aid regrowth.
If you suspect an infestation, scout before treating. Because armyworms hide during the day, use a sudsy drench test mix 3-4 tablespoons of lemon-scented dish soap with two gallons of water and pour it over one square yard of turf.
If nine or more caterpillars appear, treatment may be necessary. Smaller caterpillars respond well to Bacillus thuringiensis kurstaki (Bt), while larger ones may need synthetic pyrethroids.
Always follow pesticide labels and refer to expert sources like Michigan State University Extension for treatment guidelines. Remember, infestations are typically sporadic, and vigilance is your best defense.
Photo Credit: pexels-nikolett-emmert
Categories: Pennsylvania, Crops, Corn, Soybeans