Caterpillars start out a pale orange, and become a paler yellow with blackening inside the body. The orange head black blotches on the sides of the 'collar'. Two black spots on each side of the first segment begin a line of translucent spots along the body. They feed on evening primrose, redbud, and grape leaves. Groups of larvae use their silk to tie bunches of leaves together. Each will choose a leaf and roll, or fold, it up, creating a tube to both hide in and feed from by day, leaving leaf skeletons behind. At night, caterpillars move on to fresh leaves. Once summer is over and leaves begin drying, caterpillars fold down the edges of the leaf they are inside and fall to the ground with it. They pupate in this protective, inconspicuous cover and emerge as winged adults in the spring.
Because the dark green top and light green bottom of a grape leaf is different, spotting the presence of caterpillars is as easy as noticing the change in color on a section of the plant. Small patches of infestation may be tolerated. Parasitic wasps, predatory flies and other insect-eating bugs naturally reduce the population of Grape Leaffolder caterpillars. Spraying appropriate insecticides on the vines that are affected is also effective. Populations without control can chew up enough foliage to weaken fruit production the next year. If too much leaf coverage is eaten, ripening fruit may experience damage from overexposure to sunlight.