Southwestern Corn Borer

Common: Southwestern Corn Borer

Scientific: Diatrea grandiosella

Crop Hosts: Principally corn. Also found on sorghum.

Identification and Life Cycle: The winter is passed as full grown larvae stage located mostly in thetap roots of old cornstalks. When feeding, the 1-inch long larvae areconspicuously spotted with 8 dark spots. The insect is found in thelower part of the stalk. In early spring the overwintering larvaepupate inside the stalk and the nocturnal adult emerges a few dayslater. The female lays 300 to 400 eggs on the underside of leaves. Theworms hatching from these eggs feed on the leaves for a short timebefore boring into the stem. The first-generation worms become fullgrown by midsummer. The second generation reach maturity in the earlyfall and may remain as larvae during the winter. There are 1 to 3generations per year.

Geographical Distribution: Limited to the southern states.

Damage and Treatment: This is a very destructive insect. The worms enter the stalk and moveup and down the pith. The result is a twisted, stunted plant showingmany holes along the leaves which have been eaten out while stillcurled in the heart of the plant.