Fall armyworms are mainly pests of bermudagrass lawns, and as their name implies, they are most common in late summer and fall. It is the larva, or caterpillar, stage that causes damage by eating the grass blades with their chewing mouthparts. Fall armyworm larvae have three pairs of true legs just behind the head, as well as five pairs of “prolegs” along their abdomen. These pests can appear as early as late June in the southern portion of the state. During high outbreak years, fall armyworms may feed on centipedegrass or St. Augustinegrass, but this is rare.
Fall armyworm adults (moths) are active at night. Female moths deposit egg masses containing about 150 eggs on grass stems or leaves. Females can lay up to 1,000 eggs. After hatching, the young larvae first feed as a group on the grass blades. The damage at this stage is slight and often goes unnoticed. But as the larvae grow, they require more food and can strip a lawn quickly. To prevent this, make regular lawn inspections, beginning in early summer.
Select locations at random throughout the lawn, and examine the grass by rubbing it briskly back and forth with your hand; then part the grass and examine the ground. If you see coiled light tan or green to nearly black caterpillars, you probably have fall armyworms. Control is much easier if you find worms early, when they are small. This also helps keep lawn damage to a minimum. Do not water turf after treating for fall armyworms, as this would wash the insecticide out of where the insects are feeding. Liquid sprays are generally more effective than granular treatments.
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