2024 Author: Gavin MacAdam | [email protected]. Last modified: 2023-12-16 13:38
The southern gray weevil mainly lives in the southwestern part of Russia. Harmful beetles feed on winter and spring crops, as well as tobacco, corn, sunflowers, beets and all kinds of weeds. And voracious larvae prefer only corn. Most of all, gray southern weevils love young shoots, the full development of which is blocked by these parasites. In addition to the leaves, the bugs also gnaw the growth cones. And, although the crops do not dry out, they may well not give the expected harvest
Meet the pest
The gray southern weevil is a black pest beetle ranging in size from 6, 5 to 8 mm, densely covered with hair-like scales of grayish shades. On the sides, such scales are lighter and thicker; the sides of its pronotum form a keel-like ridge and are slightly spread. The gray southern weevil has an external resemblance to the ordinary gray weevil, however, it differs from the second by the presence of developed wings - it flies perfectly. Its elytra are usually striped and oblong-ovoid. And between the seams and the humeral tubercles in voracious insects, you can see stripes of darker shades. The beetles are active mainly in warm sundials, hiding under the soil lumps during a cold snap.
The yellowish white eggs of these garden parasites are about 1 mm in size. And the length of the curved legless larvae ranges from 8 to 10 mm. The last segments and heads are painted in gray-brown tones. Beetles hibernate deep in the soil - the depth of their wintering places is often from 40 to 80 cm. The main wintering place is corn crops, on which the development of larvae has completed. Another part of the bugs overwinters in areas where sunflower grew, and a very small part of them - where a variety of grain crops are grown. Overwintered individuals get out of the soil for a rather long time - over 20 days. And 10 - 12 days later, gray southern weevils mate.
Throughout May, harmful parasites lay eggs en masse. Sometimes this process continues with them until July. As a rule, eggs are laid by females in groups of five to seven. Eggs are placed in the soil, at a depth of twenty centimeters, closer to the forage vegetation. Fertility of each female averages about three hundred eggs. The development of larvae takes about two to two and a half months. During this time, the larvae have time to develop at four instars. And after this time, they pupate and remain in the pupal stage from seventeen to twenty days. In appearance, the pupa resembles already formed adults - one can notice in them slightly pronounced rudiments of wings, legs and rostrum.
The bugs that appeared in the first ten days of August remain to winter in cradles organized in the soil. Until spring, about ninety percent of the bugs that come out to the surface survive as soon as the thermometer rises to ten degrees. Only one generation of gray southern weevils develops per year.
How to fight
Crops in a crop rotation should be rotated in such a way as to completely exclude the possibility of re-sowing maize over maize. No less important is the systematic elimination of weeds (sow thistles and dodders are especially attractive to pests) and the spatial isolation of corn crops from the areas of mass wintering of southern gray weevils. Sunflower, like corn, is recommended to be sown early.
Corn seeds should be treated with insecticides before sowing. Some gardeners use ammonia water as a fertilizer. And if there are one or two parasites for every square meter, then the crops begin to be treated with permitted insecticides.
In general, measures used to combat common beet weevils are also suitable for the fight against gray southern weevils.
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