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. Eggs hatch and young larvae develop into adults in about two weeks. Adults live for three weeks, during which females may lay over 100 eggs. A warm, sunny, dry summer encourages reproduction and survival.
Thrips build up on alfalfa, small grains, and weeds.
As alfalfa is cut for hay, and small grains are maturing and cut for threshing, movements of thrips to and from large acreages are intensified. When cabbage is nearby, thrips can infest it. Thrips feed on leaves by puncturing and rasping the outer leaf tissue and sucking the sap as it exudes from the cells. Where many thrips have fed, the discolored areas coalesce to form large brownish, blister-like areas. Nonpersistent contact insecticides are usually unsatisfactory for controlling thrips unless used on a regular schedule during head formation.