Armyworms attack corn, grains, grasses, and other garden crops. These pests do not overwinter in cold-winter areas, but the moths migrate great distances in the spring in search of places to lay their eggs. The tan to gray adult moths lay eggs on the blades of grasses and grains. The caterpillars that hatch from these eggs feed on corn leaves, ears, and ear stalks. They get their name from their feeding habits. After they have eaten everything in one area, they crawl in droves to another area in search of more food. After several weeks of feeding they pupate in the soil, then emerge as adult moths to repeat the cycle. There are several generations each year, beginning in mid-May. These pests are most numerous after cold, wet spring weather that slows the development of the natural parasites and diseases that help keep the population in check.
When the worms are first seen, spray with an insecticide containing carbaryl or diazinon. It may be 4 or 5 days before results are seen. Repeat at weekly intervals if the plants become reinfested. To control worms that bore into the ears, spray when 10 percent of the ears show silk, and repeat 3 or 4 more times at intervals of 3 days.
Plant Care for Corn