Malicious Hessian Fly

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Video: Malicious Hessian Fly

Video: Malicious Hessian Fly
Video: Identifying Hessian Fly in Wheat Crops 2024, March
Malicious Hessian Fly
Malicious Hessian Fly
Anonim
Malicious Hessian Fly
Malicious Hessian Fly

The Hessian fly is a pest of cereal crops. Rye and barley and winter wheat are especially loved by this wretch. It lives almost everywhere - this pest cannot be found only in mountainous areas. The Hessian fly inflicts the greatest damage in the steppe. Crops heavily damaged by these pests have the appearance of pounded or beaten by hail, which will certainly affect the volume of the crop

Meet the pest

Outwardly, Hessian flies are somewhat similar to tiny mosquitoes with a brownish or dark gray color. The abdomen of females often has a reddish tint. The body size of Hessian flies is from 2.5 to 3.5 mm, and the length of their oval slightly shiny eggs is approximately 0.5 mm. The initially laid eggs of these parasites are transparent with orangeish specks, and after some time they darken.

The worm-like larvae of the first instar reach a length of about 1 mm and are colored reddish-yellow, and the length of the larvae of the next instar is about 4 - 5 mm and their color will already be greenish or milky-white. Overwintering of gluttonous larvae takes place on the ladders of winter crops, wheatgrass, and also volunteers. The larvae that did not have time to complete their development and form puparia often die in cold winters, since they are extremely sensitive to low temperatures.

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Hessian flies pupate with the onset of spring. And the flight of flies is rather uneven and somewhat stretched - it starts after the average daily temperature reaches 10 - 12 degrees. As for the calendar dates of summer flies, they fall mainly in April (the second half of it) and May. Simply put, they coincide with the end of tillering, as well as with the first half of the stage of the emergence of grown winter crops into tubules. Hessian flies differ from Swedish flies in that they mate immediately after departure and can lay eggs without any additional food at all. As a rule, this happens when the thermometer rises to 14 - 16 degrees.

The life span of females is from two to seven days. During this period, the pests manage to lay from 46 to 500 eggs (on average, about 180). The eggs of parasites are placed in chains consisting of several pieces, mainly on the topsides of leaf blades of spring and winter grain crops.

The embryonic development of Hessian flies takes approximately four to eight days. Eggs, like young larvae, are extremely sensitive to rather low humidity and high temperatures. The reborn larvae move along the flaky plates to their bases, where subsequently, having penetrated deep into the leaves, they feed on the juices of the stalks. As for spring crops, pests are placed on them closer to the foot of the shoots, thereby suppressing the development of crops and their growth. If the spring is dry enough, then such an active pest activity can even lead to the death of vegetation. And at the stage of entering the tubes of winter crops, the stalks in the feeding places of the larvae noticeably become thinner, and characteristic small knees appear on the damaged vegetation. The same picture is observed on spring crops damaged by second generation larvae. On average, from one to four, and sometimes thirty to fifty larvae develop on each stalk.

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The harmful larvae that have completed their development pupate immediately. The years of the second generation, which attack mainly spring crops, coincides with the stage of earing the crops and the appearance of grains. In dry hot weather during this period, a huge number of larvae fall into diapause, which continues until the end of summer. The researchers managed to establish that in the southern regions of Russia, in conditions of rainy and moderately warm summer, 4 - 5 generations of these cereal enemies often develop.

How to fight

When sowing winter crops, it is important to isolate them from spring crops. You should also observe the crop rotation and the most optimal sowing time for a particular zone. The best solution is to grow stem pest resistant varieties. No less important measures are the destruction of wheatgrass foci, rather deep autumn plowing and stubble plowing.

As for chemical treatments, they are advised to be carried out only if there is a need to protect the most valuable crops or in the centers of mass breeding of Hessian flies. It will be advisable to use chemicals and in the case of the presence of 5 - 10% of damaged stems during the start of the mass summer of pests. During this period, spraying with "Phosphamide", "Metaphos" or "Chlorophos" is used.

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