Why can some moth and butterfly larvae become serious crop and forest pests?

Moth and butterfly larvae, known as caterpillars, can become serious crop and forest pests primarily due to their voracious appetites and specialized feeding habits.1

These larvae are primary consumers of green plants, and many species have evolved to feed on nearly every part of a plant, including leaves, buds, stems, roots, fruits, and seeds. Because they grow rapidly, they require significant amounts of food, often consuming large quantities of plant matter daily. For example, the cabbage looper can eat three times its body weight in leaf material in a single day.231

Their impact as pests is further compounded by:
* Destructive Feeding: Many species are specialized borers that tunnel into woody stems, stalks, or terminal shoots of trees and crops, which can kill or severely weaken the plant.24
* Contamination: Beyond direct consumption, larvae often foul crops with their excrement (frass) or spin silken webs that bind plant parts together, rendering produce unsaleable.14
* Stored Product Infestation: Certain species, such as the flour moth, have adapted to feed on stored grains and cereals, causing significant economic loss in agricultural storage.24