Thrips and measures to combat them

thrips and measures to combat them Blog

Thrips are small insects that damage various plant crops. Wheat, rye and oat thrips cause the greatest damage to cereals.

Wheat thrips.
An adult insect is brown or black, with two pairs of wings darkened at the base. The body length of wheat thrips is from one and a half to two mm. The mouthparts of thrips are sucking. Their eggs are white and very small. Thrips larvae are dark red, with two setae on the last segment.

Thrips damage spring and winter wheat, less often rye. They suck juices from wheat grains (rarely from grains of other plants) and spikelet scales, which leads to underdevelopment of the spike, as a result of which the scales become discolored and the grain becomes frail and light.

Thrips are widespread in the forest-steppe and steppe zones. These pests produce one generation per year. Thrips overwinter in the larval phase in the upper layers of the soil and partly in the root zone. In spring, thrips larvae come to the surface and turn into pronymphs. This phase lasts from one week to three and a half. Adult wheat thrips appear during the period when grain cereals are eared.

After mating, the female thrips lay their eggs on the spike stem behind the spikelet scales, in groups of several pieces each. Egg laying in thrips is stretched and can last more than a month. Egg development lasts about a week or less. The thrips larvae emerging from the eggs pass to the grain. At the end of summer – during the harvesting period, thrips larvae leave for wintering.

An effective measure to combat wheat thrips is deep plowing of a piece of land after harvesting and in the spring before sowing. This method of thrips control destroys up to 90% of thrips wintering in the ground. There are also various chemicals, but most of them are toxic.

Rye thrips.
Rye thrips are black-brown insects, about 1.5 mm long. The males of these insects are wingless. Thrips females lay white, very small eggs. The larvae are pale yellow, about 2 mm long. Thrips damage the rye by sucking out the juices, causing the tops of the ears to die off. From sucking larvae, the upper part of the leaf becomes discolored (whitens) or reddens.

Measures to combat rye thrips : deep plowing of the land at the edges of the site, as well as ditches on roadsides, complete destruction of weeds on which these thrips overwinter.

Oat thrips.
Adult oat thrips up to 0.9 mm long, yellowish-gray or gray-brown. Their front wings have two, and the hind wings have one longitudinal vein. Thrips eggs are white and small. Thrips larvae are yellowish-gray in color. The last abdominal segment on the upper side with subulate outgrowths. Both adult oat thrips and larvae are harmful.

Adult thrips feed on spikelet scales and flower films of oats and wild oats, while larvae also damage grain. From the sucking of thrips larvae, the spikelet scales turn brown, the grain becomes lethargic and resembles ripened grain.

It is found throughout central Russia and the CIS countries, almost everywhere where oats are grown. In oat thrips, only one generation develops during the year. In the spring, thrips appear in the field 14-20 days before the oats begin to ear.

Females lay 3-4 eggs per day in the tissue of glumes, inside the folded leaf until the panicle is ejected. The female’s fertility is about a hundred eggs. The duration of development of the larvae of oat thrips is from 7 to 10 days.

Mature larvae go into the soil to a depth of 50 cm, where they turn into a pronymph, and then into an adult insect. Adult thrips with wings do not emerge on the soil surface in autumn; on the contrary, they descend even deeper into the soil, where they remain until the end of the next spring.

Most adult thrips hibernate in the ground at a depth of up to 750 mm.

Measures to combat oat thrips are the same as with the first two species. And the most effective way to deal with oat thrips is early sowing. Sowing must be done before the thrips return from wintering.

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