What are caterpillars?
Caterpillars are the larvae of butterflies and moths. Butterflies and moths form the order Lepidoptera, a very large group with more than 150,000 species, that are easily distinguishable from other insects. Many of the butterfly species that are active during the day can be strikingly colourful while moth flying at night are usually inconspicuously brownish are greyish. Adult butterflies do not damage crops. Most of them feed on nectar. In contrast, the caterpillars have biting and chewing mouthparts and can devour large amounts of plant tissue. Many species cause damage to crops.
The most harmful caterpillars that occur in greenhouses belong to the Noctuidae (the noctuid or owl moths), which is the largest of all lepidopteran families. Most adults of this family are nocturnal. The caterpillars mostly pupate in the ground. Another family containing several species that damage greenhouse crops is the leafroller family, the Tortricidae. The name ‘leafroller’ refers to the fact that the caterpillars often live in rolled-up leaves. Although some species are restricted to a single crop, most are polyphagous.
Caterpillars can cause serious economic damage. Most species feed on leaves and young shoots, and their enormous feeding capacity can rapidly decimate a plant. Very small caterpillars are not able to chew and therefore graze the underside of leaves. This causes a window effect where the epidermis of the upper leaf surface remains undamaged. Young caterpillars are often found in groups, spreading out over the plant as they grow larger. As their size increases, so too does the damage they inflict: leaves are often skeletonized, with only the mid-rib left intact. Flowers, fruits and growing tips can also be eaten by larger caterpillars. Some species mine in leaves or bore holes into fruit or stems, making them difficult to detect and control. In addition to consumption of the plant, caterpillars also spoil the plant with the large quantities of frass they leave behind.