2024 Author: Gavin MacAdam | [email protected]. Last modified: 2023-12-16 13:38
The gray bristly weevil most often lives in the forest-steppe zone, and a little less often it can be found in the steppe. This pest damages mainly perennial and year-old legumes: lentils with beans and clover, as well as sainfoin and sweet clover with peas. He will not refuse to feast on alfalfa with lupine, as well as some other wild legumes. Attacks of gray bristly weevils often lead to the complete destruction of leaves on the stairs of a huge number of legumes, including peas, which in turn adversely affects the volume of the crop
Meet the pest
The gray bristly weevil is a bug that can vary in size from 2.8 to 4.5 mm. In the posterior half of the elytra of these pests, long pale setae can be seen, and their pronotum are equipped with three oblong pale stripes.
The size of the eggs of these gluttonous parasites is 0.2-0.3 mm. Freshly laid eggs are initially painted in yellowish-white tones, and after a certain time they turn black. Slightly curved larvae grow up to 4 - 5 mm in length. They are painted in whitish shades and are endowed with light brownish heads. The entire body of the larvae is covered with reddish and rather long hairs. And pale yellow pupae reach 4, 5 - 6 mm in size.
Wintering of harmful beetles takes place in the soil, mainly on leguminous crops, where they fed all summer and part of autumn. And bugs wake up as soon as the air temperature begins to warm up to three to four degrees. As soon as the thermometer rises to twelve to fourteen degrees, they are activated, and when the air warms up to thirteen to seventeen degrees, they also begin to fly. Migrating bugs colonize the stairs of annuals and perennials with incredible speed. Spring reproduction of gray bristly weevils, depending on weather conditions, usually takes from five to seven days. However, in dry weather with frequent cold snaps or with sudden changes in weather conditions, the breeding of voracious scoundrels can last up to twenty days.
Approximately from the second half of April, a massive flight of bugs begins. Already in the very first warm spring days, they begin to damage the leaves of perennial legumes. At first, the bugs feed inactively, making grooves nibbled from the edges on the growing young leaves. And with the establishment of sunny warm weather, the damage caused by them becomes massive. At the same time, the bugs quite actively climb the stairs of leguminous annuals and perennials and begin to eat there.
In the forest-steppe zone, harmful parasites always begin to lay eggs only after completing additional feeding. And they are located mainly on the stalks or on the soil. Sometimes they can be seen on the leaves, however, when they dry out, the eggs still almost always roll onto the ground. The average duration of embryonic development of harmful parasites is seven to eight days. And already from May to June, a massive revival of larvae is noted, which subsequently develop for forty days.
The hatched larvae feed mainly on lentils, broad beans, as well as peas, lupines and a number of other crops. After some time, they pupate. In the forest-steppe zone, it occurs approximately in the first ten days of June, and in years characterized by cold spring - in the second half of it. Most pupae concentrate at a depth of ten to twelve centimeters in the soil, and the average duration of pests at this stage is nine to thirteen days. In the second and at the beginning of the third decade of June, bugs of a new generation fly out. As for the steppe zone, there they emerge at the end of May or in the first half of June. Thus, the full development cycle of these voracious parasites takes from forty-five to sixty days. Young bugs immediately start feeding on crops with juicy green organs. From peas, they gradually move to lentils with fodder beans and other legumes. And a little later they migrate to perennial legumes (to sweet clover with clover, etc.), where they feed until they are sent for wintering.
How to fight
For preventive purposes, it is recommended to sow all crops in a short time, while sowing leguminous crops should preferably be placed away from areas with perennial legumes. Acidic soils must be limed. And after harvesting all legumes, it is necessary to thoroughly plow the areas.
In order to destroy bugs, they are sprayed with barium chloride (about 400 g of it will be needed for ten liters of water) or Parisian greenery (for ten liters of water, 40 g of lime and 20 g of Parisian greenery are taken).
The complete absence of precipitation in the period from May to June, when their mass revival starts, also leads to a significant decrease in the number of harmful larvae.
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