The soybean looper, Chrysodeixis includens (Walker), is a light to dark green caterpillar that takes its name from its preferred host plant and the looping movement it makes while in motion.
This pest is an abundant caterpillar across much of North and South America and all of Central America. It overwinters only in South Florida and South Texas in the U.S. Although it ranges across much of the U.S., infestations of economic importance rarely occur north of southern states ranging from Texas, Arkansas, Mississippi, Alabama, Florida, Georgia, and South Carolina.
In its larval stage, the soybean looper is predominantly light to dark green and typically has white stripes running down the dorsal and lateral portions of its body. C. includens can be differentiated from similar-looking species by inspecting the number of abdominal prolegs. Green caterpillars with three or more abdominal prolegs can be easily distinguished from C. includens, which has only two abdominal prolegs. The soybean looper may have black or green thoracic legs, while the cabbage looper has green thoracic legs. The adult moth is small, with a wingspan ranging 1 to 1.5 inches, and it’s mottled brown to black in color.
Although soybean is the preferred host, it also feeds on other agronomic crops such as peanut, cotton, corn, vegetables, and floricultural crops. Vegetables attacked include crucifers, sweet potatoes, tomatoes, bell peppers, beans, cucumber, and watermelon. Larvae (caterpillars) consume large amounts of foliage and will also feed on pods and fruits, while moths feed solely on nectar.
Moths deposit eggs at night in the lower half of the canopy on the underside of leaves. After hatching, the insect typically transitions through six instars. Once hatched, the soybean looper feeds in the lower half of the canopy where the egg was laid.
The soybean looper has an unusual defoliation pattern, feeding from the lower, inside canopy and then moving up and outward. Because of this feeding pattern and cryptic coloration, it can be easily overlooked while scouting.
Caterpillars generally feed for two to three weeks before pupating. Pupation occurs on the underside of leaves and is completed in seven to nine days, with moths emerging during the day. Pupae are ½ inch long and range in color from white to green.
Predators and parasitoids prey on soybean loopers and may help suppress populations. Bt formulations may be used to suppress this foliage feeder and spare beneficial insects in the field.
Due to its wide host range, C. includens has developed resistance to many insecticides. Resistance has been confirmed for pyrethroid, carbamate, and organophosphate insecticides.