Pests: find out more THRIPS

Thrips

The Pest

There are many species of thrips found in Britain, several of which may occasionally attack crops. The most common species found on protected crops are Thrips tabaci (onion thrips) and more recently Frankliniella occidentalis (western flower thrips or W.F.T.).

Thrips feed on many types of crops causing damage to leaves and scarring to both flowers and fruit. Damage to leaves can be recognised by the appearance of white flecks with black spots (droppings) in them. If the damage is severe, leaves become totally "silvered" and many young and adult thrips can be seen underneath the leaf and in the flowers. Thrips can also transmit viruses such as tomato spotted wilt virus, which is damaging to a range of crops.

Thrips damage on
tomatoes

Thrips are small, slender insects, about 1-1.5mm long when adult.  The larvae are wingless and once the wing buds develop the larvae is then termed a pre-pupa.  Adult thrips have narrow fringed wings.  The colour of thrips depends on the species, varying from greyish-yellow to black.

Adult thrips lay their eggs beneath the leaf cuticle. The females cut a hole into the plant before depositing an egg. The eggs hatch, and the young wingless larvae start to feed on the leaf surface, and in the flowers. After a couple of larval stages the pre-pupal larvae usually fall to the floor and find a sheltered place in which to pupate. The resulting adults emerge from the pupae and fly onto the plants, start to feed, and lay eggs.

Thrips can come into the glasshouse from outside, be brought in on plant material and overwinter.  They can be easily distributed on air currents, equipment, plants and clothing.  At any time in an established population a large proportion will be pupating and it is in this way that the pest is carried over from year to year.

 
Thrips larva

Thrips in Cucumber
flower