Due to their excellent natural adaptation thrips have developed to be one of the most feared and widespread pests. They cause serious damage to vegetable crops as well as ornamentals and soft fruit.
Thrips damage the crop by withdrawing plant cell fluids. Empty cells are filled with air, causing a silvery appearance, on which dark spots (the excrements) are visible. Moreover, many more damage symptoms may occur depending on the crop. For instance, thrips on very young cucumber fruits give deformed fruits. In sweet pepper, they cause cosmetic damage on the fruits close to the calyx. In several ornamentals, flower damage through discoloration or deformation occurs. Only a few individual thrips are enough to cause severe damage. Moreover, thrips are important vectors of several viruses (e.g. tomato spotted wilt virus, TSWV).
Adult thrips are small, elongated insects with typical fringed wings. They measure about 1 mm, and have a grayish or yellow to brown colour. Female thrips deposits eggs in the leaf cuticle tissue. The eggs hatch within a few days into very mobile larvae which immediately start to feed. After the second instar larva they let themselves fall to the ground to pupate. The total development time from egg to adult takes from 20 days at 20°C (68°F) to 12 days at 30°C (86°F). At sufficiently high temperatures one female thrips can produce up to 200 descendants.
The two most common harmful species are the onion thrips (Thrips tabaci) and the western flower thrips (Frankliniella occidentalis).