Most flowers are susceptible to damage from caterpillars of one or more species. Caterpillars are the immature or larval stage of moths and butterflies. Only the larval stage chews plants. Although adults consume only liquids, such as nectar and water, they are important because they choose which plants to lay eggs on. Larvae have three pairs of legs on the thorax (the area immediately behind the head) and leglike appendages on some, but not all, segments of the abdomen.
Identification of species
Moths and butterflies have complete metamorphosis and develop through four life stages. Adults have prominent, delicate wings covered with tiny scales that rub off and appear powdery when touched. After mating, the female moth or butterfly lays her eggs singly or in a mass on or near the host plant or nearby soil. Eggs usually hatch in several days. The emerging larvae move singly or in groups to feeding sites on the plant.
Most caterpillars eat voraciously and grow rapidly. Some feed almost continuously. Others, such as cutworm larvae, hide in the soil during the day, emerging to feed at night. Caterpillars shed their old skins about five times before entering a nonactive pupal stage. Some species pupate in silken cocoons, and most species pupate in a characteristic location, such as on the host plant or in litter beneath the plant.
The adult moth or butterfly emerges from the pupal case after several days to several months, depending on the species and season. Some common caterpillars have only one generation per year outdoors; other species have several generations each year and can cause damage throughout the growing season.
Caterpillars chew irregular holes in foliage or blossoms or entirely consume seedlings, young shoots, buds, leaves, or flowers. Some caterpillars fold or roll leaves together with silk to form shelters. Caterpillar feeding can kill or retard the growth of young plants.
Handpick. Eliminate nearby weeds, which may host caterpillars. Provide proper cultural care to allow older plants to outgrow and replace any damaged tissue after infestations are controlled. Applications of Bacillus thuringiensis or spinosad can be effective against larvae, especially when caterpillars are small. Natural control by viral diseases, general predators, and parasites (Hyposoter, Copidosoma, Trichogramma) is often effective.
For more information on leafrollers, see the Leafrollers on Ornamental and Fruit Trees Pest Note. See also Leaf-feeding Caterpillars Quick Tip.