2024 Author: Gavin MacAdam | [email protected]. Last modified: 2023-12-16 13:38
The bean weevil is distributed by local foci in the zones of growing beans. In addition to the fact that it damages absolutely all types of beans, it also does not refuse to feast on peas in granaries. And in the case of artificial settlement, this pest damages soybeans and very valuable forage beans. Most often, the enemies of the beans attack the earliest crops
Meet the pest
A bean weevil is a beetle whose size ranges from 2.8 to 3.5 mm. From above it is covered with grayish hairs forming countless vague specks. The pronotum of this bean lover is bell-shaped, with no teeth on the sides, and below, on the inner edges of the thighs of the hind legs, it has one sharp tooth, followed by 2 - 3 such teeth.
The size of small oval eggs of the parasite is 0.5 - 0.7 mm. They are dull, white, sometimes slightly bent. The tiny cylindrical larvae, measuring approximately 4 mm in length, are rather strongly curved and equipped with rather long bristles. And the larvae of younger ages are characterized by three pairs of legs that disappear when they reach the next century. The size of the yellow-white pupae is approximately 3-4 mm.
Enemies of beans hibernate not only in storages inside the grains, but also in the field - under the numerous remains of all kinds of plants, in the ground, and also in carrion. Individuals that have settled in warehouses reproduce at a high rate in summer and slower in other seasons (for example, in winter). And in rather warm rooms, these parasites are able to multiply continuously throughout the year, developing in five to six generations. Well, in the field, the development of the enemies of beans takes place in one generation, and only in the south of Russia they can sometimes form a second, so-called optional generation.
In spring, the beetles begin to scatter from their wintering grounds at a distance of up to three kilometers and begin feeding on flowers, petals, as well as pollen and generative organs of various legumes. At the beginning of the formation of beans, they populate the beans, and mass colonization occurs already at the stage of ripening of these beans. Numerous eggs are laid on their valves, as well as in holes gnawed by females in the dorsal seams of the beans, small cracks or wrinkles by harmful bugs. The laying period takes on average 12 - 18 days, and the total fertility of females of the enemy bean reaches about 50 - 60 eggs. Embryos develop in the field, depending on temperature, from six to eleven days. The harmful larvae that leave the eggs immediately bite first into the beans, and a little later into the grains. Their full development in summer is completed in 21 days, and 8 - 10 days are enough for the development of pupae.
Bean kernels are classified as thermophilic type with a constant need for high air humidity (from 75 to 90 percent). The upper temperature threshold of their development is considered to be 36.3 degrees, the lower one is 14, and the most optimal for parasites will be the range from 18.7 to 30.3 degrees. Bean kernels are unusually sensitive to low positive and especially negative temperatures. Beetles outside the grains die in 15 days at temperatures from 0 to 2 degrees, in 10 days - at 4 degrees, and in a day or two - at temperatures from 12 to 18 degrees.
In one grain, up to 18 - 30 harmful larvae can often coexist, destroying the grain almost entirely. The entire development cycle of bean weevils takes place in the grain, from which the beetles then get out through the rounded holes formed by them. Early bean crops suffer from this parasite to a greater extent, while later ones are less damaged due to the fact that they have asynchrony in the ripening of beans and in the timing of the emergence of beetles.
How to fight
In order to prevent attacks of bean weevil, it is recommended to sow seeds free from it. Beans should be harvested in a timely manner as soon as they begin to crack.
Cooling the grain is also a good measure - the pest does not tolerate low temperatures. If you send the crop to the freezer for three days, there will be no trace of the parasite.
Heating the beans in the oven for three minutes will be no less effective - although the skin of the grains shrinks a little, this will not affect the taste of the beans in any way. And pests that did not withstand the heat will die. After this procedure, the cooled beans are placed in jars under plastic lids and placed in a cold place.
When storing beans in bags, cut garlic cloves are placed on their bottom or dill seeds are poured - the bean weevil, intolerant of such aromas, also quickly retreats.
When a bean weevil appears on the site at the beginning of the formation of beans, the crops can be sprayed with insecticides.
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