Wheat thrips: developmental features, natural enemies and ways to combat pest

Farmers are well aware of the damage that small wheat thrips can cause to a grain crop. The result of his life is a decrease in the quality of grain, its sowing value is deteriorating. Spring wheat suffers the most. A whole range of measures has been developed to combat pest. It includes chemical processing of fields and agricultural activities.

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Wheat thrips (Haplothripstritici) belongs to the family Phalaeothripidae, including large insects. The length of the imago is 1.5-2.3 mm. The body is long, thin, painted dark brown or black. The head is equal in length to the pronotum. The oral apparatus is a piercing-sucking type. The eyes are large, black. The edge of the forehead is beveled and serves as the base of the mouth cone. Antennae consist of 8 segments. The second segment is yellowish-brown, the third is yellow. There are several setae on the prothorax, narrowing is observed in the middle part.

The abdomen consists of 10 segments. Wings are elongated, with thin venation. Along the edges are framed by long cilia. For this structural feature, thrips are called fringed-winged. The front and rear pair of wings are the same length. On the legs of the running legs are vesiculate suckers. Fore tibia and tarsi yellow. Sexual dimorphism is noticeable in the sizes of individuals: the female is 1.8-2.3 mm, the male is 1.2-1.5 mm.

Distribution area

The habitat of wheat thrips covers Europe, North Africa, Asia Minor, Kazakhstan. In Russia, the pest is found everywhere in Siberia.

Insect development

Young thrips appear in May-June; the time coincides with the beginning of winter wheat heading. The attack on the fields is carried out by air. Insects fly at a height of 1.5-2 m. They prefer to eat behind the vagina of the penultimate leaf of an ear. At this site, they can suck out the juices from the tender part of the plant's wrapper. During the period of spring wheat heading, pests massively migrate to it. With the beginning of cracking of the spike wrapper, females secrete pheromones and attract males for mating.

Information. Females in the pest population are 2-3 times more than males. In some regions, males are found in a single amount. This does not prevent reproduction; females lay unfertilized eggs.

Ovipositor occurs on the inside of the ears of corn. In clutch 4-8 eggs are yellow or orange, oval. The length is 0.4-0.6 mm. The breeding period takes about a month, the fertility of the female is 25-28 pieces. The embryo develops 7-8 days. At birth, the larvae are light green, but soon acquire a bright red color. Larvae cause major damage to plants. They suck the juice from the spikelet scales, and then from the grain.

The development of larvae takes more than six months. Having spawned, they feed on the juice of young grain. This period continues until the waxy maturity of the grains. By this time, the larvae have time to shed. They stop feeding and sink into the basal part of the stubble. In this phase they remain to winter. Some insects burrow into the soil to a depth of 10-20 cm, others hide under plant debris. With the arrival of heat, when the earth warms up to + 8 °, the larvae turn into pronimph, then into nymphs.In this state, stay 1-2 weeks. The next stage is the imago. The yield of adult insects is extended for a month. Life expectancy of adults is 30-40 days.

Information. One generation of wheat thrips is replaced in a year.

Harm

The main feed crops of wheat thrips are winter and spring wheat, rye. It harms barley, buckwheat, oats, corn, feeds on wild cereals and herbaceous plants. The adults are damaged by leaves; after their exposure, light spots appear. The ears from which the juice was sucked out are deformed, there is friability, whiteness. In places where the larvae are punctured, the grain becomes stained.

With a massive defeat of crops, the weight of the grain decreases, the quality of the flour and seed material decreases. On infected plants, up to 100 individuals can live at the same time, including adults and larvae. When the number of larvae is 30 pieces, the weight loss is 12-15%. The habitat of 40-50 larvae on an ear is considered a threshold of harmfulness.

Warm, dry weather contributes to the active development of pests. Prolonged drought and rain negatively affect the number of insects. During metamorphosis, nymphs die from lack of moisture. Long rains cause damage to the larvae with fungal infections. Among the natural enemies that exterminate wheat thrips: ktyr, ground beetles, ladybugs, carnivorous thrips, lacewing larvae, bedbugs.

Methods of struggle

After studying the features of the development of wheat thrips, effective control measures were developed. The main methods of pest control are agrotechnical measures and insecticidal treatment.

Agrotechnical measures

Agrotechnical methods include:

Autumn plowing of the soil allows to destroy up to 80-90% of larvae.
Compliance with crop rotation.
Timely stubble peeling.
Sowing spring crops in the early stages, the use of early ripening wheat varieties. It is a fact that late varieties are infected 2-4 times more.

Chemical way

Chemical treatment of the fields is recommended at the beginning of wheat earing. The procedure leads to the death of most egg-laying females. Insecticides lead to the destruction of other pests: grain scoops, aphids, turtles. To spray the fields, systemic and contact-intestinal chemicals are used - Ditox, Fufanon, Fastak, Clonrin.

At the beginning of summer, farmers have time to process crops before the pest penetrates the grain. The fight against wheat thrips is complicated by the fact that on the ears there are insects of different ages, which are hidden behind the leaves and scales of grain. Only comprehensive measures can completely get rid of the pest.