Stenchaetothrips biformis

Scientific Name Stenchaetothrips biformis
Synonyms Thrips oryzae
Common Names English: Rice thrips; Spanish: Trips del arroz; German: Reis-Blasenfuß; French: Thrips du riz
Description Adults of S. biformis are brownish-black, about 1-2 mm (0.04 - 0.08 inch) long, and are either wingless or have narrow, elongated, heavily-fringed wings which are folded along the body at rest.
Young larvae are almost transparent, but become yellowish-white after their first molt.

Biology

Damage

Larvae and adults of rice thrips puncture plant cells with their mouthparts and ingest their contents. The insects prefer to feed on the growing tips of young leaves, which consequently roll inwards at the margins. The patches of empty and therefore translucent epidermis cells appear as silvery streaks. Later, they turn yellow-brown, and as infestation progresses, the leaves start wilting from the tip down and become 'scorched'. Plants will be stunted and in severe cases, they may be killed completely.
This thrips species apparently attacks only seedlings or young plants. Rice is particularly susceptible under water stress, e.g. during the dry season.

Lifecycle

The adult female cuts slits into the leaf epidermis with its ovipositor and inserts one of its 25-150 eggs into each of them, so that the upper halves of the eggs remain exposed.
After 3-6 days, the larvae hatch. The two larval instars, which both ingest food, are followed by the comparatively inactive prepupal and pupal stages, which do not feed. The whole development cycle can be completed in less than 2 weeks. Normally, all stages remain inside the rolled leaves; even the mobile adults hide there most of the time, except for migration. They are easily transported by the wind over long distances and thus spread to newly-planted rice fields or to other graminaceous hosts, on which they may also hibernate during the cool season in temperate regions.
The adults fly during daylight - females much more than males - and are not attracted to light traps. Their peak of activity is mostly during the morning. The lifespan is 2-3 weeks for males and 3-4 weeks for females.
In the tropics, rice thrips is most abundant during the dry season, which often coincides with the seedling stage of rice. At these times, population density can multiply rapidly.

Occurrence

Additional Crop Information

Stenchaetothrips biformis is economically important mainly on rice, although it sometimes occurs on sugarcane and corn. It is, however, polyphageous on many other grass species, including cereal crops.

Agricultural Importance

S. biformis is found in the rice-growing regions of Asia, in Africa, Europe and Oceania.
In 1994, it was detected for the first time in South-America (Guyana) and may start to spread there, too. The economical importance of rice thrips varies between seasons and growing areas. In many countries, it is generally considered a minor pest. However during outbreaks - which occur particularly during long, dry periods - crop losses can reach 100%.

Control

Integrated Crop Management

Damage by rice thrips is much more severe when the plants are under water stress. Late-planted rice is more susceptible to injury.
Several traditional rice varieties are resistant to thrips.
Rice thrips populations can be significantly reduced by flooding the field to submerge the plants for about 2 days.

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