These spots look burned or browned out. This appearance is the result of grass plants rapidly dehydrating after fall armyworm larvae have chewed off the tender foliage. For this reason, fall armyworm damage often resembles drought damage. Fall armyworm damage on closely mowed grass. Note brown patches resembling drought damage.
Brown patches appear in the field and can rapidly increase in size.
Fall armyworm damage in a hayfield. Caterpillars have eaten the tender, green portions of the grass, leaving jabbed leaf edges and tough leaf bases. Established, healthy, bermudagrass is rarely killed by fall armyworms, but the complete defoliation caused by a severe infestation weakens plants and deprives livestock of pasture or a hay producer of a hay cutting. Fall armyworm damage on newly established grasses including winter annuals, tall fescue, or orchardgrass can be an even more serious situation. Seedlings of these fall-seeded plants are small when populations of fall armyworm are at seasonal highs.