Flowers or leaves may develop silvery streaks. Heavily infested leaves appear brownish or silvery and growing points may become contorted. Some species of thrips leave sooty spots of black fecal matter on the leaves. Thrips also vector plant diseases. Light blue cards coated with a thin film of oil suspended within two feet above indoor plants can be used as indicator traps.
Winged adults caught on the card indicate the presence of thrips.
Life Cycle Female thrips lay their eggs in tiny slits cut into the surface of leaves, flowers and stems. The eggs can be laid any time of year and hatch within a few days in warm, indoor conditions. The young, called nymphs, are cream to pale green and only visible with magnification. They feed for 7-14 days. Full grown nymphs, in most species, drop off the plant to the soil where they burrow down and pupate.