Armyworms, also called caterpillar moths, cause a tremendous amount of damage to trees, grass and crops. They can attain a length of about 1½ inches (3.8 centimeters). When armyworms are small their bodies have a greenish color, but they turn brown when they're fully grown. The adult armyworm is a brownish-grey moth with a wingspan of about 1½ inches (3.8 centimeters). Female armyworms can lay 1,000 eggs over a few nights. Within a few days, the eggs hatch and the caterpillars begin feeding on turf. They will devour the grass down to the ground. Moths emerge after a couple of weeks. Large larvae feed voraciously and can completely consume leaf tissue [source: Pugh]. We will now look at ways of killing armyworms.
- Natural controls Some kinds of brachonid wasps and tachinid flies help keep armyworms in check. The red-nailed tachinid fly, in particular, lays eggs on the armyworm's back. The tachinid larvae bore into the armyworms to feed. There are also several types of ground beetles that prey on armyworms. Birds, toads and skunks can also help keep armyworms in check.
- Cultural control Keep grassy weeds under control to avoid attracting egg-laying adults. Avoid planting susceptible crops in low wet areas, as that attracts the adult caterpillars. Don't spray herbicide on the grass, as that will drive the caterpillars to lay their eggs on the vegetables [source: University of Wisconsin].
- Chemical controls There are various chemicals that are approved for use against armyworms that will not harm your crops. These insecticides often have to be applied daily to protect your crops [source: Capinera].