Nodule weevil - bean pest

Nodule weevils - the generalized name of the beetle family, in which there are about 100 species. Meet insects can only bean crops. Young larvae infect nodules and plant roots, while adult beetles gnaw at leaves and growth points. If you do not take measures to control pests, the yield of green mass and seeds is reduced several times.

Biological features of beetles

Insects are common throughout Europe with a warm climate. Most species of nodule weevils winter in the adult insect phase and only a few species spend the winter months in the larval stage. The sizes of adult beetles vary from 3 to 8 mm. The nodule weevil has a number of distinguishing features:

• a small square tube nearly square;
• elytra covered with bristles and scales of light gray shades;
• bulging eyes with cilia of white or black;
• red claws with claws;
• The oval back is decorated with dark stripes or spots.

There are no obvious differences, except for the structure of the genital organs, in females and males.

Interesting!

Nodule weevil is a very shy creature. Sensing danger, he imitates a dead insect.

With the onset of spring at a temperature of + 5 ° C, the awakening of insects begins. However, their activity is manifested in warmer weather conditions, when the thermometer reaches + 15 ° С. Nodule weevils begin to migrate in search of pea plantations, fields planted with alfalfa, vetch, kidney beans, lentils. The settlement period lasts from 5 to 20 days and depends on weather conditions. In cloudy or rainy weather years weevils not observed, however, on hot days, the settlement of crops occurs rapidly. Infested bugs can cause significant damage to seedlings. According to the observations of biologists after resettlement, insects lead a sedentary lifestyle.

After winter, adult beetles need food and eat young upper leaves of legumes. They do this somewhat sophisticatedly, figuratively gnawing ovals on the edges of foliage. There are cases when numerous colonies of weevils completely destroyed the leaves on pea shoots and other leguminous plants.

Interesting!

The female is almost three times more gluttonous than the male. On average, she gnaws on a sheet of 10 mm², and the male only 3.3 mm². A particularly hungry individual can eat up to 16 mm ² per day.

Reproduction and development of weevils

Nodule weevils are famous not only for gluttony, but also for fertility. Oviposition begins in late spring. One female lays up to 30 eggs per day, in her short life she is able to produce up to 30 eggs. The female does not choose special places and scatters eggs randomly. Initially, the embryos are light in color and covered with a sticky membrane that holds the eggs on leaves and stems. Gradually, they roll to the ground, become almost black in color and mix with the soil during rains.

Important!

Temperature above 32 ° C and the absence of rain lead to mass death of eggs. Temperature and humidity also affect the development of embryos.

Egg development lasts from 6 to 30 days, then a mobile legless larva with a small head and without eyes appears from it. A young insect climbs under the soil, where it finds nodules of plants. You can determine the entry point of the larva by a dark speck. Having penetrated the nodule, it begins to absorb all the contents. After one shell remains from the tuber, the larva moves to the next. In the larval phase, one insect destroys 5-6 nodules.

After eating a few nodules, the larva grows in size and does not fit in the tubers, so it begins to eat the outer tissues of the roots. On one pea plant, there can simultaneously be up to 20 young individuals. The development of the larva lasts from 25 to 40 days, depending on the climate of the habitat and weather conditions. The ripened larva is buried in the soil to a depth of 10-15 cm and equips itself with a cradle for pupation. After 9-14 days, a young beetle leaves the pupa. The newborn nodule weevil begins to eat intensely and eats the juicy leaves of peas, alfalfa wiki. After harvesting annual crops, insects fly on perennial leguminous grasses, where they remain for wintering.

Common types of nodule weevils

The most numerous and widespread species is the striped nodule weevil. Distributed in Europe and Asia. The length of the beetle does not exceed 6 mm, and it can be distinguished from other weevils by the absence of cilia. There are nodule weevils on peas, lentils, less often on alfalfa and clover.

Nodule bristly weevil rarely grows larger than 4.5 mm. White cilia are placed above the bulging eyes. Elytra densely covered with short black setae and long white hairs. Prefers to develop on peas, clovers and annual legumes.

The yellow-footed weevil is covered with numerous recesses and has flat eyes. Distributed in the European part of the country and in the North Caucasus. Clover and alfalfa are preferred.

Clover nodule weevil is the smallest representative of a large family of pests. Its dimensions barely reach 3 mm. The prothorax is outlined by 3 bright lines, the body without hairs and bristles. It feeds on clover, for which it got its name.

Nodule pea weevil is a generalized popular name for pests of pea plantations. These include striped and bristled beetles.

Maliciousness and Pest Control

Damage to agricultural crops is brought by both adult bugs and young larvae. They harm young crops, spoil the root system, which ultimately leads to the death of plants or a decrease in seed yield, green leaf mass. Measures to combat nodule weevil include agronomic measures and chemical methods:

• thorough cleaning of plant debris and plowing the soil;
• soil and seed treatment with insecticides;
• sowing annual legumes in the early stages;
• regular destruction of weeds and loosening of the soil;
• the destruction of beetles on plants with a solution of barium chloride;
• liming of acidic soils.

In the plots of land after harvesting annual legumes, poisoned baits are left.