🪖 Armyworm
Spodoptera frugiperda
They march, they munch, they leave your lawn looking like a bad haircut.
How to identify
Striped caterpillars about 1 to 1.5 inches long, dark with lengthwise stripes and an inverted pale 'Y' on the head capsule — check with a hand lens, it's the ID clincher. Fall armyworms range from green to nearly black depending on what they've been eating.
Damage signs
They chew ragged holes in leaves and can defoliate seedlings overnight; on corn they burrow into whorls and ears, leaving frass that looks like wet sawdust. In turf they march in literal armies, stripping grass to stubble in expanding brown patches.
Plants it attacks
Corn, sorghum, turfgrass, bermudagrass, rice, millet, vegetable seedlings
Non-chemical controls
- Scout at dawn or dusk when they feed — handpick caterpillars and drop them in soapy water.
- Spray the biological bacterium Bacillus thuringiensis (Bt) on foliage; it only activates inside caterpillar guts, so bees, ladybugs, and you are unaffected.
- Attract parasitic wasps and tachinid flies with nectar plants like sweet alyssum and buckwheat — their larvae do the killing for you.
- Till or disturb the soil in fall to expose overwintering pupae to birds and cold.
- Use pheromone traps to monitor moth flights so you can act before eggs hatch — one trap per garden corner works.
- Protect corn whorls by sprinkling a pinch of sand or diatomaceous earth into each whorl — it abrades the young larvae.
Nerdy fact: The 'army' name is literal: when they strip one area bare, thousands march shoulder-to-shoulder to the next food source like a tiny invading force with no supply lines and no mercy.