Caterpillars (Lepidoptera)

Many species of Lepidoptera attack flower and foliage crops. None of them are exclusively pests of greenhouse crops, but feed on a wide variety of agricultural and horticultural crops, inside and outside of greenhouses. Some major pests include beet armyworms (Spodoptera exigua), cabbage loopers (Trichoplusia ni), cutworms, such as the variegated cutworm (Peridroma saucia) (Family Noctuidae), European corn borer (Ostrinia nubilalis), (Family Pyralidae) and the omnivorous leafroller (Platynota stultana) (Family Tortricidae). Occasionally, other pests, including woolybear caterpillars (Family Arctiidae) find their way into greenhouses and cause localized plant damage

A generalized life cycle of Lepidoptera is shown in Figure 1. Adults of the species listed above (except Arctiidae) are rather dull-colored moths that generally are most active at night or on dark days. Adults may be attracted into greenhouses by lights used in plant production. Sometimes moths enter greenhouses when outdoor crops are harvested, or decline because of adverse weather. Eggs are laid singly or in masses, generally on undersides of leaves. Larvae hatching from the eggs feed on plants - on leaves or flowers. Some may bore into stems, while others roll or tie leaves together. Some species (e.g. the beet armyworm) may do all of these things at certain times during their development.

Beet armyworms (Figure 2), (Figure 3), (Figure 4), (Figure 5) are major pests of chrysanthemums and other plants in southern and western parts of the United States. Occasionally, plants in northern states are also attacked. Eggs are laid in masses of about 100 on undersides of leaves, and hatch in two to nine days. Young larvae often are found feeding near shoot tips, and often web young leaves together. Sometimes feeding by small larvae will "pinch" plants and cause branching. Older larvae feed on leaves and flowers, and may bore into stems and buds. Larvae are indistinctly striped, green to almost black caterpillars, about 1.25 inches (3 cm) long when fully developed. There usually is a prominent dark spot just behind the head area on an older larva. Larvae develop in seven to 16 days, then pupate Adults emerge four to 11 days later.

Cabbage loopers (Figure 6) feed on foliage and flowers of numerous plants. Eggs are laid singly on leaves. After seven to 10 days, the eggs hatch, and the tiny larvae begin to feed. Larvae are pale green, with white stripes on each side and along the back. They are called loopers because of the way in which the larvae move. Larvae develop for two to three weeks, consuming progressively more plant tissue as they grow. When fully developed, larvae are about 1.25 inches (3 cm) long. Pupation usually occurs on leaf undersides, and the adults emerge in 10 to 14 days.

Cutworms are caterpillars that normally spend daylight hours beneath pots or potting media, feeding on plants at night. Feeding by some cutworms may cut plants off at the base of the stem. Leaves, buds, and flowers may be damaged by other species called climbing cutworms. The variegated cutworm (Figure 7) is a climbing species. Adults lay several hundred eggs, which hatch in four to five days. Cutworm larvae are variable in color, but generally are gray to black, sometimes with yellow or white stripes and spots. Larval development takes 20 to 35 days. When fully developed larvae may be 2 inches (5 cm) long. Cutworm infestations are usually localized.

Omnivorous leafrollers ( Figure 8 and Figure 9) can be problems on numerous flower and foliage crops, including rose, poinsettia and geranium. Adults lay eggs in greenish clusters on host plant leaves. Eggs hatch in seven to nine days, and the young larvae begin to feed on leaves. At first, leaves are skeletonized or simply "gouged." Later, larvae tie or roll leaves together with webbing. Larval development takes 30 to 50 days, and pupation occurs on the plants. Adults emerge in about 10 days.

European corn borers ( Figure 10 and Figure 11) have occasionally caused problems on crops such as garden chrysanthemums produced near cornfields. Eggs are laid in masses of 15 to 35 on undersides of leaves. Eggs hatch in about seven days, and young larvae feed on foliage for a short time before boring into stems. Sometimes the only sign of a corn borer infestation is a small entrance hole in the stem surrounded by powdery sawdust-like material called frass. Larval development takes about 30 days.

Woolybear caterpillars (Figure 12)are other occasional visitors to greenhouse crops, particularly late in the outdoor growing season. Adults (called tiger moths) probably wander into greenhouse by accident. Eggs are laid in masses on plant leaves, and the larvae feed on foliage. Woolybear larvae can be distinguished from all of the other species listed above because they are very hairy.