Prevention and eradication

Thrips in natural size

Fig. 15 Thrips, natural size.

Thrips fought quite vigorously when seen as pests on plants, but once they are flying and are numerous, there is nothing to do outdoors. The thrips which make it inside, die very quickly – the climate inside is too dry for them. If you are not willing to wait for them to die naturally, they can be eradicated with an insect spray with pyrethrin I and II + piperonyl butoxide. It’s hard to effectively keep thrips out. They fly through fly screens; however, if doors and windows are kept closed on flying days, and spray before-mentioned pyrethrin in the cracks, it is possible to tone down the discomfort.

Life cycle (Thrips)

Thrips season in August

Fig. 14. Thrips are mostly troublesome in August.

Thrips live on plants. They suck the sap out of the leaves, and the affected areas often appear to be shimmering because air enters into the empty cells. Some thrips are considered pests. The thrip eggs are laid within the plant tissue with a saw-like ovipositor. The male thrips are very rare; therefore, the eggs develop without fertilization. Thrips go through four larval stages.

Thrips are good fliers, but they only fly on calm, warm summer days. They are predominantly an outdoor phenomenon; however, they are also seen on greenhouse plants and indoor plants and can sometimes stray into houses in large numbers.

They crawl into narrow crevices and you can often find dead thrips behind wallpaper, behind the glass of images and similar places. Some thrips make little awkward leaps hitting the abdomen into the ground or whatever surface, they are on. This is reminiscent of fleas.

Thrips

Thrips

Fig. 13.
Thrips.

Thrips

Thrips

Thrips (Thysanoptera) are also known as thunder flies, thunder bugs, storm flies, thunder blights, storm bugs, corn flies and corn lice. Their legs usually end in two tarsal segments with a bladder-like structure and their four very wings have ciliated fringes on the edges.

In Denmark, there are more than 100 different thrips species and it is difficult to distinguish between them. Most are small, less than 2 mm long, black or brownish. The head of a thrip is bent downward and backward, and its mouth parts form a short, cone-shaped tube enclosing three stylets used to pierce the cell wall of tissues.

Thrips

( Latin:   Order Thysanoptera)

These are very small, often dark insects, forming a quite distinct order. Each of the legs ends in a protrusible vesicle, and the two pairs of very narrow wings have hairy edges. In Denmark they are sometimes known as cholera flies. This is because they occurred in enormous numbers in Copenhagen during the cholera year 1853, and it was erroneously thought that they had some connexion with the disease.

Most thrips are associated with plants, where they feed on the sap.

They fly very well, but normally only take to the wing on warm, still days. They may then occur in enormous numbers and can be very irritating when they crawl around on the skin producing a tickling sensation, and because they have a tendency to creep beneath clothing and into ears, mouth and eyes. Although, as already mentioned, they are plant suckers their mouthparts can penetrate human skin.

Under certain circumstances thrips enter houses in large numbers. They have a special habit of creeping into narrow spaces and they are therefore found behind wallpaper and even behind the glass of pictures. However, they soon die in the dry climate of modern houses. The species usually seen is Limnothrips cerealium.

Thrips

These are very small, often dark insects, forming a quite distinct order. Each of the legs ends in a protrusible vesicle, and the two pairs of very narrow wings have hairy edges. In Denmark they are sometimes known as cholera flies. This is because they occurred in enormous numbers in Copenhagen during the cholera year 1853, and it was erroneously thought that they had some connexion with the disease.
Most thrips are associated with plants, where they feed on the sap.
They fly very well, but normally only take to the wing on warm, still days. They may then occur in enormous numbers and can be very irritating when they crawl around on the skin producing a tickling sensation, and because they have a tendency to creep beneath clothing and into ears, mouth and eyes. Although, as already mentioned, they are plant suckers their mouthparts can penetrate human skin.
Under certain circumstances thrips enter houses in large numbers. They have a special habit of creeping into narrow spaces and they are therefore found behind wallpaper and even behind the glass of pictures. However, they soon die in the dry climate of modern houses. The species usually seen is Limnothrips cerealium.

Thrips

Thrips

Thrips

(Latin: Thysanoptera)

On warm summer days the tiny insects known as thrips may occur in enormous numbers and even enter houses. They have a tendency to creep in under clothing, or into ears, mouths and eyes, and they tickle as they move around on the skin.

Thrips feed by sucking plant juices, but occasionally they may insert their mouth- parts into human skin, in some cases causing a rash and itching. They can jump by striking the abdomen against the substrate and are therefore sometimes confused with fleas.