Beetroot weevil: types of pests and methods of control

In early spring, small inconspicuous bugs appear in the fields. Weevils wintered in the soil crawl in search of food. The basis of their diet is beet leaves. Beetles eat young shoots of vegetables. Beetroot weevil is widely distributed in the European part of Russia, in the Central, West Siberian and North Caucasus region. Two weevils are most harmful: common and gray. Agrotechnical measures and chemicals are used to control insects.

Common beet weevil: species description

A common pest of sugar, table and fodder beets is the common beet weevil. The insect belongs to the order of beetles, the family of weevils. The length of the imago is 10-15 mm. The black body of the beetle is covered with numerous light scales and hairs, giving it an earthy-gray color. In the middle of the elytra there is a dark intermittent strip. Closer to the end of the body, two white prominent spots formed by scales are noticeable.

Beetroot weevil belongs to the group of short-trunked. Its rostrum is short and furrowed. The eyes are large, located on the sides of the head. Antennae cranked, ending with a mace. Pronotum wider than head, laterally covered with short, overlapping scales. Elytra parallel, rounded at apex. Under them are well-developed wings. Abdomen is light with many black spots.

Sexual dimorphism

The female beet weevil is larger than the male. In males, the first two segments of the abdomen have a longitudinal fossa. The third segment of the paw of insects is bifurcated; in males it is larger. The final section of walking legs in females is less pubescent with hairs.

Larva

The meaty body of the larva differs in an arcuate shape. She has no legs. The head is yellow or brownish yellow. The body length is 28-30 mm. White colour. The body consists of 12 segments, 9 spiracles on the sides. Towards the last fifth age, hairs appear on some parts of the body.

Information. Larvae of the first age are 1.5 mm long; their body is covered with spines.

Features of development and nutrition

Beetles hibernate in the adult phase, burrowing into the soil by 25-45 cm. In spring, when the temperature rises to + 6-7 °, they crawl to the surface. At first, weevils move sluggishly, but with an increase in temperature to 22-25 ° the mass years of insects begin. At first, the beetles feed on weeds of the family of malaria (quinoa, knotweed, shiritsa). With the advent of seedlings of beets, they move to the leaves. Weevils eat the sprouts, slowing down or stopping the growth of the crop.

Beetles are active in the daytime. In favorable conditions (warm, moderate wind, low humidity) they make long flights at an altitude of 4-5 m. During the day, insects travels up to 10 km with rest. The optimal hours for flying from 11 to 16. After additional nutrition, beet weevils become sexually mature.

The mating period is the end of April - the beginning of May.Fertilized females masonry for several months. Light yellow eggs 1.2 mm long are laid in the soil next to the feed plant. During the breeding season, the female leaves 200-300 eggs. For them, a hole up to 1 cm deep is dug up with a cephalotube. The masonry intensity increases in warm sunny weather. The adults who gave birth to offspring die off.

Information. The duration of the pupal phase is 10-20 days. The bulk of weevils does not leave the cradle, but remains to winter in the soil. Under adverse conditions, the output is delayed for 1-2 years.

Insect harmfulness

The larva appears 7-12 days after masonry. She changes five ages after four links. The offspring goes deeper into the soil by 15 cm, where it feeds on the roots of beets. On one plant there are several dozen pests that gnaw at the roots. The consequences of exposure are:

• root deformation;
• reduction in sugar content;
• death of a part of crops;
• the mass of the vegetable is reduced.

Through the damaged cover, the beets become infected with fungal and bacterial infections that cause decay. The development of the larva takes 45-90 days. Then she turns into a chrysalis. After 2 weeks, a young beetle is born. In warm weather, it gets to the surface, but in most cases remains in the ground until next spring. One generation is replaced in a year.

Gray beet weevil: pest description

A polyphagous pest, gray beet weevil, feeds not only on the main fodder plant, but also on legumes, sunflowers, onions, grapes, garlic and other crops. Tanymecyspalliattus is a small beetle 9-12 mm long. It is characterized by a uniform body color. Numerous spots are absent on its body; the weevil is covered with brownish hairs and gray setae. On convex elytra humeral tubercles stand out.

The sides and bottom are light. Wings are underdeveloped, beetles are deprived of the ability to fly.

The rostrum is short and thickened. Antennae long, club-shaped, cranked. The mouth apparatus is gnawing. Long walking legs are covered with hairs and bristles. Larva small (up to 12 mm), light, slightly curved. Head and chest are yellow in color. On the upper torso segment a strong brown plate. Pupa elongated; at this stage, the rudiments of all organs of the weevil are clearly distinguishable.

Lifestyle

Adults and larvae leave for wintering; two generations develop in a year. Pests fall into diapause at a depth of 20-25 cm, less often drop to 65 cm. A signal to activity is a temperature increase of up to + 10 °. Gray weevils wake up later than other species. Having risen to the surface, the beetles begin to search for food. Feeds on any weeds. After satisfying the first hunger, they go in search of their favorite fodder plants.

Overwintered beetles cause the greatest harm to vegetables. They eat leaves and damage the growth point, from which seedlings die. Insects move on the ground, therefore they cannot overcome long distances and obstacles. Adults are active in warm sunny weather. They do not tolerate cold well, try to bury themselves in the ground or hide under lumps of soil.

Breeding

During the breeding season, weevils become more active. After mating, prolific females lay 200-700 eggs in the soil. The masonry is located next to the fodder plants. Adults die at the end of summer. Larvae appear after 18-20 days. Mobile offspring quickly penetrates the soil, getting close to the roots.

Interesting fact. The number of eggs depends on the female feed plant. The greatest fecundity is observed when eating on a bindweed.

Larvae develop 13-25 months, pass 10 ages. They are typically buried in the soil by 100-200 cm. At this depth, they are not afraid of frost and fungal infections. After wintering, the larvae rise in the upper layers of the soil and continue feeding. In the second year of life pupate. The pupal phase takes 3 weeks.Young beetles are reflected at the end of summer, but leave the soil next spring.

Methods of struggle

Gray and common weevils harm beet crops throughout the European territory of Russia to Lake Baikal. In household plots, the pest can be collected manually. For fields, this method is not suitable; special agricultural techniques are needed.

Attention. The number of weevils is controlled by natural enemies: birds (starlings, crows, rooks), ground beetles, predatory mites, tahini.

Agrotechnical measures

The main agricultural activities include:

• weed removal in the fields;
• deep plowing after harvesting;
• the introduction of mineral fertilizing;
• use of high-quality seed material;
• Compliance with the technology of growing crops;
• isolation of infected sites.

Use of insecticides

A significant spread of pests threatens the quality of the crop. In such a situation, the use of insecticides cannot be dispensed with. Among the recommended drugs:

1. Kinfos is a concentrated emulsion of contact-intestinal action.
2. Clonrin is a systemic pesticide.
3. Alphafans is an intestinal insecticide.
4. Actellik is an organophosphate pesticide.