Interesting Facts About Thrips: Pests Of Commercial Crops

Thrips are minute, agile insects of the order Thysanoptera. They have piercing-and-sucking mouthparts and cup-shaped feet from which bladderlike adhesive organs may be extended. Some species are wingless, but many have four narrow, featherlike wings fringed with hairs. Metamorphosis is gradual, and some thrips frequently reproduce by parthenogenesis.
A few species prey on mites and small insects; others, e.g., the onion, pear, greenhouse, and grass thrips, feed on the foliage and flowers of plants to which they may transmit virus diseases. Thrips are classified in the phylum Arthropoda, class Insecta, order Thysanoptera.
Thrips are minute, slender insects with fringed wings and unique asymmetrical mouthparts. Different thrips species feed mostly on plants by puncturing and sucking up the contents, although a few are predators.
Almost 6,000 species have been described. They fly only weakly and their feathery wings are unsuitable for conventional flight; instead, thrips exploit an unusual mechanism, clap and fling, to create lift using an unsteady circulation pattern with transient vortices near the wings.
Many thrips species are pests of commercially important crops. A few species serve as vectors for over 20 viruses that cause plant disease, especially the Tospoviruses. Some species of thrips are beneficial as pollinators or as predators of other insects or mites.
In the right conditions, such as in greenhouses, many species can exponentially increase in population size and form large swarms because of a lack of natural predators coupled with their ability to reproduce asexually, making them an irritation to humans. Their identification to species by standard morphological characters is often challenging.
Here are some interesting facts about thrips:
1. Some flower-feeding thrips pollinate the flowers they are feeding on, and some authors suspect that they may have been among the first insects to evolve a pollinating relationship with their host plants.
Scirtothrips dorsalis carries pollen of commercially important chili peppers. Darwin found that thrips couldn’t be kept out by any netting when he conducted experiments by keeping away larger pollinators.
2. Thrips develop resistance to insecticides easily and there is constant research on how to control them. This makes thrips ideal as models for testing the effectiveness of new pesticides and methods.
Due to their small sizes and high rates of reproduction, thrips are difficult to control using classical biological control. Suitable predators must be small and slender enough to penetrate the crevices where thrips hide while feeding, and they must prey extensively on eggs and larvae to be effective.
3. Many thrips are pests of commercial crops due to the damage caused by feeding on developing flowers or vegetables, causing discoloration, deformities, and reduced marketability of the crop. Some thrips serve as vectors for plant diseases, such as tospoviruses. Over 20 plant-infecting viruses are known to be transmitted by thrips, but perversely, less than a dozen of the described species are known to vector tospoviruses.
4. Apart from active flight, thrips, even wingless ones, can also be picked up by winds and transferred long distances. During warm and humid weather, adults may climb to the tips of plants to leap and catch air current. Wind-aided dispersal of species has been recorded over 1600 km of sea between Australia and South Island of New Zealand.
A hazard of flight for very small insects such as thrips is the possibility of being trapped by water. Thrips have non-wetting bodies and have the ability to ascend a meniscus by arching their bodies and working their way head-first and upwards along the water surface in order to escape.
5. Flower-feeding thrips are often attracted to bright floral colors (including white, blue, and especially yellow), and will land and attempt to feed. It is not uncommon for some species to “bite” humans under such circumstances. Although no species feed on blood and no known animal disease is transmitted by thrips, some skin irritation has been described.

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