16 Dec 2016

Thrips


Thrips are the most serious of home and garden pest of vegetables, flowers, strawberries and other soft fruits.

Thrips damage plants directly by feeding and laying eggs on the plant, and indirectly by acting as vectors for viruses such as tomato spotted wilt virus and impatiens necrotic spot virus. Thrips are very tiny flies. In the summer they fly around in the garden, and feed by burrowing into plant tissue or developing leaves and buds. In open garden they tend to cause most damage from June to September, but in glasshouses they can often start in April.

OVERVIEW

Thrips found in the British Isles are tiny insects, just 1-2mm long, but in other parts of the world they can be up to 14mm.They have two pairs of narrow fringed wings, although some are known to be wingless.

The adults lay there eggs in a pocket in the leaf, and the larvae emerge to feed on the plant; growing buds and flower buds are particular targets. Young thrips (larvae) are similar to the adult, but without wings. The very young are white, and the older ones are yellow/brown. The larvae live on the plant, but when they pupate they often drop to the soil. The pupae can hide on the soil for several days and sometimes several months before the adult emerges.

Thrips suck the juices out of the plants leaves and emerging flowers. Depending on the host species, feeding injuries occur on fruit, flowers, flower buds, leaves, and leaf buds Leaf scars and specks of black feces are a good way of diagnosing the presence of thrips on plants. In some host species, thrips feeding causes flower or leaf buds to abort or emerging leaves to become distorted. Feeding does not always result in immediately visible damage because many flowering species do not show injury until flower buds open. When thrips feed on flowers, symptoms include streaks and discoloration of the petals—with dark flowers showing light streaks and light flowers showing dark streaks.