This damage is not as harmful as it appears and seldom results in loss of yield. However, extremely high populations of three to six larvae per plant in the whorl stage may cause damage to the developing head or growing point and justifies treatment at these levels. Sorghum Webworm Corn earworm and fall armyworm infestations in grain sorghum heads are generally below treatment level except in late crops. Early planting practices that encourage the development of beneficial insect populations aid in the control of armyworms and earworms. The corn earworm is more common than fall armyworm, but both species are readily abundant.
Infestations are more damaging in tight headed sorghum varieties than in open heading varieties.
Inspect sorghum heads soon after flowering and continue through the soft dough stage. The sorghum webworm is one of the most common pests of sorghum in Arkansas. Large numbers of webworms, especially in late planted sorghum, can occur in heads where they gnaw circular holes in maturing seed and feed on the starchy contents. Apply an approved insecticide when you find five or more larvae per head. Insecticides for Control of Fall Armyworm, Corn Earworm and Sorghum Webworm.