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Common Turfgrass Insects: CATERPILLARS

Fall armyworm,
caterpillar stage

Caterpillars are the immature stages of moths and butterflies. They have chewing mouthparts and feed mainly on foliage.

Damage

Blades of grass damaged by caterpillars often appear ragged or may be skeletonized with only the leaf veins and one surface of the leaf remaining. Close examination of the thatch around damaged grass often reveals silk webbing and "frass" (excrement) left by the caterpillars. Damage often is spotty or localized. Several species of caterpillars can be found in Texas turfgrass.

Common Species

Armyworms are grayish brown caterpillars that may grow to 1 1/4-inch in length. They often have a cream colored upside-down "Y" on the fronts of their head capsules. True armyworms appear in the spring, while fall armyworms (see image) appear in August and September following a wet summer. Tips of grass turn white from feeding by the young larvae.

Cutworms also are dull-colored caterpillars. Cutworms curl up tightlywhen disturbed. They appear in early spring, feed at night and are found in the soil during the day. Leaves and stems are cut off by caterpillars but may not be eaten.

Sod webworm caterpillars also feed during the night. During the day, they burrow into the thatch or soil. Young larvae skeletonize blades of grass. Older larvae cut off grass completely and form tunnels of silk in the grass.

The tropical sod webworm has been particularly damaging in recent years to turfgrass in the upper coastal region of Texas. Caterpillars of this species are translucent cream or greenish with dark spots.

Management

Action levels for some turf caterpillars have been proposed. For armyworms and cutworms, a suggested action threshold is four to five caterpillars per square foot. For sod webworms, treatment should be initiated when three to four caterpillars per 6 square inches of turf are detected using the soapy water drench method. Begin to inspect for damage 2 weeks after peak adult flight is detected with a black light trap.

Other Common Insects of Turfgrass