ECONOMIC INJURY LEVELS FOR WESTERN FLOWER THRIPS (THYSANOPTERA, THRIPIDAE) ON GREENHOUSE SWEET-PEPPER

Low, medium and high densities of western flower thrips, Frankliniella occidentalis (Pergande), were established in 3 greenhouses at the Gre enhouse and Processing Crops Research Centre, Ontario, Canada, in 1994 and 1995 to develop economic injury levels for thrips on greenhouse s weet pepper. Pest densities were monitored weekly using yellow sticky traps. Fruit was harvested weekly, graded for size, weighed, and rated for thrips damage using 3 damage categories. Fruit damage was signifi cantly related to thrips density. Economic injury levels ranged from 1 0 to 26 adult thrips per sticky trap per day, depending on the seasona l stage of sweet pepper production and market prices. These levels can be used as a guideline to assist growers in improving the timing of i nsecticide applications and for determining the upper thrips densities for effective biological control.