Older larvae feed extensively on flowers, buds, and foliage. The beet armyworm has several generations per year. Flight activity is greatest in July and August. Eggs are laid in masses of 15 to 150 mostly on the undersides of leaves and mostly within 10 cm of the soil surface. Females may cover the eggs with a mat of scales that protects them from parasites and insecticides.
Females prefer younger plants to older plants.
Two to 9 days later the eggs hatch. First and second instar beet armyworms feed in groups, especially in the growing tips where they web several leaves together. Older larvae do not restrict feeding to young leaves. The third and fourth instars last 1 to 3 days. The fifth instar feed for 2 to 6 days.