Much of Illinois is being inundated with large numbers of adult moths. We have received numerous reports of a hundred or more moths flying out of individual bushes when disturbed. The most common moths appear to be the adults of armyworm, black cutworm, and bilobed looper.
Armyworm moths are about 1 inch long, with tan to grayish brown wings. Each front wing has a single white dot near the center. There are usually two generations per year in Illinois.
Black cutworm larvae feed on a wide range of plants, including tomato transplants, young corn, and turfgrass. The adult moths are about 1 inch long, with a 2-inch wingspan. Their front wings are mottled with shades of medium to dark brown. The hind wings are light-colored. They have several generations per year.
Bilobed loopers feed as caterpillars on alfalfa, clover, cabbage, and many other plants. The moths have mottled medium brown to dark brown front wings, with a silver-colored, lopsided, figure-8 shape in the middle of the front wings. The moths have a 1- to 1-1/2–-inch wingspan. The hind wings are lighter- colored. There are several generations per year.
Many of these moths migrate from southern states. Perhaps the unseasonable warm weather that we experienced earlier in the spring aided their flight into our area. These adult moths feed on flower nectar at night. They are not a threat to any landscape plantings.
Large numbers of moths do not necessarily translate to many caterpillars later. Fungal diseases, parasitic flies and wasps, and other factors can greatly reduce caterpillar numbers. Be watchful for larval armyworm and black cutworm infestations in turf, and treat if needed. Do not make preventive applications of insecticides.