The corn earworm and fall armyworm feed in the early stages of sorghum on leaves and later on the heads. The sorghum webworm is a pest during the heading stage and feeds only in the head. Scouting Grain Sorghum for Caterpillars Scout sorghum at least once a week to detect caterpillar infestation. Scouting is very important when heads begin to emerge from the boot. Examine 100 heads per each 20 to 40 acre field and more in larger fields.
Caterpillars feeding in the heads are often difficult to detect.
Shaking the heads onto a cloth or into a white plastic bucket may help detect larvae. Count the number and kind of worms present and determine the average number of each per head. Whorl Feeders Fall Armyworm, Corn Earworms Fall armyworms and corn earworm moths often deposit eggs on the leaves of sorghum plants. Larvae of these moths vary from pale green to almost black with longitudinal stripes along the back. This damage is not as harmful as it appears and seldom results in loss of yield.