I've been getting a lot of emails in the past two weeks about "worms and/or caterpillars" in yards. Not so coincidentally, I've also had a few turf samples that I've been looking at that obviously weren't chinch bug damaged, and not take-all patch or brownpatch.
So, if you know it's not chinch bugs or grub worms and you further know that the turf damage isn't related to fungal diseases (yet), then the problem in late September and early October is more than likely cutworm, sod webworm or armyworm damage.
The larvae of several kinds of moths, such as sod webworms, cutworms and armyworms, feed on grass leaves and damage turf extensively. The insects can be distinguished by their feeding habits and injury symptoms. Sod webworms and cutworms are night feeding caterpillars. Both insects feed around a small burrow or tunnel in the turf and carry the leaf blades into the tunnel. Silken threads can be seed in the early morning covering the tunnel of the sod webworm. The cutworm is often found on golf greens after greens are aerated. The aeration holes provide an ideal habitat for the cutworm larvae during the day while feeding around the hole at night. Armyworms are appropriately named because they can be seed moving across turf in large numbers. In contrast to sod webworms and cutworms, armyworms feed during the day and night and leave the turf with a white skeletonized appearance.
Sod webworms adults are small, white to gray moths, with a snout-like projection on the front of the head. While resting, the wings of the moth are closely folded about the body. The moths are frequently seen fluttering over the turf in the early evening. The females scatter their eggs at random as they fly over the turf. Apparently the moths are attracted to dark green, healthy turf. Eggs hatch in 7 to 10 days and larvae begin feeding on grass leaves. As they mature, the larvae build silk-lined tunnels through the thatch layer and into the soil. The slender larvae reach 3/4-inch in length and are characterized by a light brown color with several rows of dark spots along the entire length of the body. The first signs of sod webworm damage are areas of unevenly clipped grass and patches of brown or closely clipped grass. The larvae remain active for several weeks, and then pupate. Adults appear about 1 week later. A life cycle is completed in 5 to 6 weeks with several generations per year.
Sod webworms are readily controlled by most liquid insecticides approved for turfgrass such as bifenthrin, malathion or any of the synthetic pyrethroids or carbamates out there. However, these are short residual materials and repeat applications are required to control next generation larvae.
The fall armyworm is the most common armyworm found on turf. The adults are grayish-colored moths with gray or white mottled wings that measure about 1° inches across. The females lay eggs in masses of a hundred or more on grass leaves and other foliage. The eggs hatch in 2 to 4 days and the tiny larvae begin feeding on tender grass blades. Newly hatched larvae are white with black heads. Their bodies darken as they feed until they are full grown. Full-grown fall armyworms are about 1° inches long and light green to almost black in color with several light stripes along the body.
Fall armyworms feed for 2 to 3 weeks, and then burrow into the soil to pupate. In 10 days to 2 weeks, the moths emerge. Several generations may occur annually
Damage may first appear as whitish patches in the lawn where the grass has been skeletonized. Later, as the larvae grow, they devour all foliage except grass stems. Fall armyworms may be seen migrating across the grass in the daytime, but they feed mostly at night. Fall armyworms can be controlled by the same materials recommended for sod webworms and cutworms.
Cutworm moths exhibit a grayish-brown to black color and a wingspread of 1 to 2 inches. The moths are active only at night. Females lay their eggs singly or in groups of 2 to 3 on the leaves and stems of grasses. Eggs hatch in 7 to 10 days and the larvae begin feeding. Cutworm larvae are grayish-black, smooth "worms" that curl into a ball or "C-shape" when disturbed. The cutworms grow into a length of 1° to 2 inches, are usually plump (in contrast to the slender sod webworm) and may be spotted or striped. There are several generations of cutworms produced annually. And while they most often appear in early spring, if the weather is just right, like right now, they will appear in fall. And tell me where you've heard this one before: The same insecticides that are good for armyworms and sod webworms will also take care of cutworms.