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The name for armyworms is appropriate, since they seem to march across the turfgrass area, leaving behind a wake of destruction. (Photo by Rick Brandenbury, Ph.D., North Carolina State University)
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Fall
is when we see the highest populations of the common late summer and early fall insect pest, the fall armyworm (go figure). Fall armyworms are caterpillars, the larvae of a small, light brown moth. The fall armyworm caterpillar reaches a maximum size of about 11/2" in length. Adult caterpillars are usually a tan color, while younger, smaller ones are often darker, almost black. The distinguishing marking on a fall armyworm is an inverted “Y” on the top of its head, leading to a line down the middle of the caterpillar’s back. Although fall armyworms can feed on a wide variety of grasses, they are especially fond of bermudagrass, and it is in bermudagrass
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that they are the worst pest. When there is a severe infestation of fall armyworms, it is easy to see how they got their name, as the advancing front of caterpillars can literally eat every blade of grass in its path, leaving behind only defoliated stems. Fall armyworms have multiple, overlapping generations, so especially at this time of the year, you will see eggs, small caterpillars, large caterpillars, pupae and adult moths all in the same patch of turfgrass. If you see a lot of moths flying over your turf, especially around dawn or dusk, look for armyworm egg masses. Armyworms usually lay their eggs in clusters of 50 to 100 on smooth, light-colored surfaces near turfgrasses. Metal gutters and fences, the undersides of plant leaves, and
metal light poles are favorite places for fall armyworm moths to lay eggs. The presence of birds digging up the grass while hunting for the caterpillars can also be an indicator of an armyworm infestation. If you see damaged bermudagrass in summer or fall, always check for fall armyworms. The caterpillars most actively feed around dawn and dusk, so check for them at those times. You can use the soap-flush method to detect fall armyworms. Put one squirt of lemon-scented dishwashing liquid in a gallon of water, and soak a small area of the turf with the soapy mixture. This will bring the armyworms to the surface in about 10–15 minutes, making it easy to see them. Of course, if the infestation is bad enough, you won’t