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True Armyworm on Wheat

Pseudaletia unipunctata (Haworth)

Description: Larvae are up to about 1 1/4" long, with a brownish green body and three dark stripes running the length of the body. The moth is pale brown and has a wingspan of about 1 1/2". There is a light spot in the center of the forewings. The egg is greenish white.

Biology: Armyworms overwinter as larvae in South Carolina. I have often found these worms in quail crops during January. After pupating in the soil, the first spring generation of moths emerge to lay eggs on small grains and other grasses. Each female may produce up to 2,000 eggs laid in small clusters. The larvae feed for about three weeks, depending on temperature and there are multiple generations per year. Armyworms feed on newly emerged leaves and immature kernels, occasionally causing significant defoliation or clipping off some heads. Usually the damage is noticed first, because the larvae hide under organic debris on the soil surface during the day.

Management: Armyworms very rarely cause significant defoliation on wheat in South Carolina. Populations are so sporadic that it is not practical to scout fields for armyworm. In nine years of annual surveys across South Carolina, we never found a field with economic populations. However, this insect is occasionally noticed feeding on wheat, and it has the potential to cause economic injury in an outbreak year. The treatment threshold is 2 larva per row ft. If armyworms are discovered, part the rows with a wooden dowel or yard stick and count the larvae between rows for a 3-ft. length. Check 6-10 representative areas in a field. Armyworms are likely to be more abundant in areas of lush growth. See the most recent issue of the Ag. Chemical Handbook for control recommendations.

Reference: Hunt, T. N. and J. R. Baker. 1982. Insect and related pests of field crops. AG-271. North Carolina Agricultural Extension Service. 214 pp.

Prepared by Jay W. Chapin, Extension Entomologist/Professor,  Department of Entomology, Soils, and Plant Sciences, Clemson University, Edisto Research & Education Center

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