Tap the plant with a pencil while holding a sheet of white paper to catch any falling insects. Since the thrips are very small and stay hidden most of the time, they are difficult to detect. Yellow or blue sticky cards placed at crop height are excellent for monitoring thrips. Blue is effective for thrips while yellow is a good all around color for trapping other insects including whiteflies and fungus gnats . One to 3 cards per 1000 sq.
Effectiveness depends on number used per sq.
Place some near vents, doors, and other openings. If you are uncertain of the identity of the insects you have trapped, contact your state inspector, the Department of Agriculture, your County Extension Agent, or the Penn State Department of Entomology for assistance. Change the cards regularly. For ease of handling, cover used cards in one layer of cellophane or similar clear plastic wrap when they are removed. Record the number of thrips trapped each week to determine if the population is increasing or decreasing.