2024 Author: Gavin MacAdam | [email protected]. Last modified: 2023-12-16 13:38
Pea caryopses love to feast on peas and live almost everywhere. As a rule, they enter pea crops together with the sown seeds. A considerable number of them fly to crops and from wintering places. Especially many pea caryopses can be seen at the end of May, when antennae begin to form on the plants, as well as during the period of bud formation and at the very beginning of flowering. Crops begin to colonize with these parasites, usually from the edges, slowly covering the remaining area. Damage to the peas contributes to a decrease in the quality of the crop and its weight. Such peas should not be eaten or fed to livestock, since the excrement of the larvae contained in them contains the dangerous alkaloid cantharidin
Meet the pest
Pea caryopses are bugs reaching 4 - 5 mm in size. They are usually painted black, and on top of their bodies are covered with small hairs. The shortened elytra do not cover the last pair of abdominal segments, on the tips of which one can observe white cruciform patterns. The tarsi of the middle legs, as well as the antennae and tibia segments of pea caryopses, are reddish.
Elliptical eggs of pests reach a length of 0.6 - 1 mm and have a yellowish color. The size of the larvae, endowed with heads retracted into the thoracic regions, ranges from 5 to 6 mm. And light yellow pupae of pea parasites reach a length of 4 - 5 mm.
Most often, the wintering of gluttonous beetles takes place in storage facilities, in grain. In the southern regions of Russia, a substantial part of the parasites overwinter in the soil, under tree bark, in the middle of vegetation remnants and in stacks of straw.
When the air warms up to 26 - 28 degrees, you can observe a massive release of harmful bugs from peas. Their output will be more extended in time at a temperature of about 20 degrees, and at 15 - 16 degrees and less it will be rather weak. The release of bugs from the grains is accelerated by high humidity. All overwintered bugs appear in May, initially concentrating on the flowering bird cherry in the gardens, as well as on numerous weeds. They feed mainly on flower petals and pollen. They are highly active on cloudy days, as well as when hot weather is established with a temperature of more than 21 degrees. The rest of the time they hide between compressed young leaves or in pea flowers.
The process of oviposition in pea weevils in the steppe zone starts in the first decade of June, and in the forest-steppe zone from mid-June. The eggs are laid by the females on top of the beans. Laying eggs begins at a temperature of 18 degrees, and when the thermometer rises to 26 - 27 degrees, you can observe a massive laying of eggs, clearly visible against the green background of ripening beans. The total fertility of females ranges from 70 to 220 eggs.
The embryonic development of parasites takes from six to ten days. The reborn larvae immediately gnaw first at the walls of the beans, and then the tissues of the green grains, which are often underdeveloped. In the resulting holes, not only their further full development takes place, but also the development of pupae with bugs of a new generation. Several voracious larvae can penetrate into the grain at one time, but only one will survive. Each larva develops in the steppe zone from 29 to 36 days, and the pupa from 13 to 18 days. In the conditions of the forest-steppe, their development takes from 36 to 37 and about 25 days, respectively. For the full development of both larvae and pupae, the most favorable temperature is from 26 to 28 degrees. And when it drops to 10 - 12 degrees, their development completely stops.
Subject to the optimal timing of harvesting peas (approximately in July), only larvae can be found in the grains, and pupae with bugs can also be found in the harvest harvested in August. The pea weevil develops in only one generation per year.
How to fight
When growing peas, it is very important to follow the rules of crop rotation. Early plowing of plots and timely collection of peas with their subsequent threshing will also do a good job. And, of course, it is best to choose resistant varieties for planting.
Sowing peas together with mustard as a support crop is also a good measure. Its pungent smell is excellent at scaring away bugs.
To a certain extent, hungry egg-eaters can help reduce the number of pea weevils.
If the infection with a pea weevil reaches ten grains per kilogram, and the moisture content of the grains does not exceed 15.5%, it is allowed to fumigate the peas with special preparations.
At the stages of budding and the start of flowering, forage and seed pea crops are sprayed with insecticides. However, this measure will be advisable if there are ten bugs for every hundred plants.
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