Pest Update: Fall Armyworms in Turfgrass
The Extension Office received multiple calls on Thursday August 26, 2021 about fall armyworm infestations in turfgrass. Fall armyworms are not true worms, but rather the larval stage of a tropical moth.
If you notice brown patches rapidly spreading in your lawn, you may have fall armyworms. Check for armyworms by mixing 2 Tbsp dish soap per gallon of water and watering the mixture into an affected area with a watering can. This will flood armyworms out of the turf. The Virginia Tech Insect Lab is recommending a treatment threshold of 3 armyworms per square foot. Armyworm infestations are sporadic. Most lawns will recover, although some overseeding may be in order.
There are a number of pesticides that can be used to treat armyworm. Look for one of the following active ingredients: azadirachtin, Bacillus thuringiensis var. kurstaki (Bt), bifenthrin, carbaryl, chlorantraniliprole, clothianidin, cyfluthrin, deltamethrin, dinotefuron, halofenozide, lambda-cyhalothrin, permethrin, spinosad, or trichlorfon. Use a product that is for lawns or turfgrass and that lists armyworms as a controlled pest. Apply products in the early evening and do not water in unless the product label instructs you to do so. Always read and follow the pesticide label.
There are some similar species out there, so we encourage you to get a positive identification by submitting good quality images to the Extension Office (firstname.lastname@example.org). You can also bring a sample by our office at 2748 Dogtown Road between the hours of 8:30-5, Monday-Friday.