Southwestern Corn Borer
Diatraea grandiosella (Dyar)

PLANTS ATTACKED: Corn, grain sorghum, Johnsongrass, broomcorn and Sudangrass.

DESCRIPTION: Adult. The front wings of the moth are yellowish brown to almost black, and bordered by gray. Wing expanse is approximately 1/4 inch. The moth is active only at night.

Larva. The full-grown larva is about 1 inch long. It is yellow and spotted conspicuously with eight rounded brown or black spots across the anterior portion of each segment. Two smaller black spots are located near the posterior margin of each segment.

LIFE HISTORY: This insect passes the winter as a full-grown larva in the taproots of the old corn or sorghum stalks. It changes to a pupa inside the stalk during early spring and emerges as an adult a few weeks later. The moth deposits flattened, whitish, oval eggs in small groups on the underside of leaves and in. an overlapping shingle fashion. The egg hatches within a few days, and the young worm feeds first upon the leaves but soon bores into the pith of the stalk. A larva may feed on several stalks. There are one to three generations annually.

DAMAGE: The damage caused by these insects often is unnoticed or the injury is attributed to other causes. Infested plants have ragged, broken and dangling leaves with many holes which were fed upon by the larvae when the leaves were curled in the heart of the plant. The worms also bore up and down the pith of the stalk and may cause the plants to lodge. Plants attacked by borers are twisted and stunted. These insects may reduce yields of corn and sorghum 15 to 50 percent.