Thrips are very small, slender insects with mouthparts specialised for sucking and rasping. Adults are 1-2 mm long, and most have a pair of narrow wings fringed with long hairs. Juveniles are wingless and often paler or lighter coloured than the adults.
Some species feed on insects and mites, and can therefore be important biological control agents, but thrips are better known as pests due to the damage that plant-feeding species cause in crops. Thrips attack a wide range of crops including vegetables, fruit trees and ornamental plants.
Thrips cause direct feeding damage when they pierce plant cells and feed on the contents. When they feed on leaves, this produces characteristic leaf ‘silvering’ and their dark droppings can usually be seen around the sites where they have fed. When they feed on fruit (such as strawberries), they drain the pigment from the cells, stripping the fruit of its colour. Thrips also feed on growing tips, buds and emerging flowers, leading to distortion of fruit and leaves, and unsightly scaring and discolouration of flower petals. Some species of thrips also transmit plant diseases.
Significant pest species include:
- Western flower thrips (Frankliniella occidentalis)
- Plague thrips (Thrips imaginis)
- Tomato thrips (Frankliniella schultzei)
- Onion thrips (Thrips tabaci)
- Greenhouse thrips (Heliothrips haemorrhoidalis)
A variety of natural enemies, including predatory mites, predatory bugs, predatory thrips, lacewings, ladybirds and parasitoid wasps, can all contribute to the control of thrips, and it is possible to achieve good results without necessarily resorting to chemical treatments.