The onion thrips, Thrips tabaci Lindeman, is a cosmopolitan insect and one of the most important and destructive pests of cabbage in Pennsylvania. If not adequately controlled, serious economic damage from immature and adult stages often results. Estimates of crop damage and losses to the cabbage industry have averaged 3 to 5 percent during the past decade.
Adults are pale yellowish to brownish, with four long, narrow wings fringed with long hairs.
Immature thrips are similar in shape to the adults, but smaller in size, wingless, and lighter in color. Onion thrips overwinter as adults in alfalfa, clover, and wheat fields. In late spring, as the daily mean temperature rises above 60o, thrips migrate to one of their many hosts. They lay eggs singly and indiscriminately in incisions made in plant tissue by a saw-like tube. More eggs are laid during the hot summer months than in cooler days.