Bright Rapeseed Sawfly

2024 Author: Gavin MacAdam | [email protected]. Last modified: 2023-12-16 13:38

The rape sawfly lives literally everywhere. Especially often you can encounter him in the steppe zone. It attacks rapeseed, radish with turnips, cabbage, turnip, as well as radish with turnip and other cabbage crops. The caterpillars of this bright pest are mainly harmful, eating leaves and small veins located on them. As a result of their harmful activity, only stems and large leaf veins remain on the plants. Rape sawflies are especially dangerous in case of early mass infection of growing crops

Meet the pest

The size of the brilliant reddish-orange-colored adults of rapeseed sawflies is 6 to 8 mm. The antennae and heads are black, and on the backs of the pests you can see a couple of black diamond-shaped spots. Each individual is endowed with two pairs of transparent wings with a yellowish base. The short abdomens of the gluttonous parasites have a yellowish-ore color. The tops of the abdomens in females are slightly pointed, while in males they are rounded.

Oval and slightly translucent eggs of harmful parasites reach 0.8-1 mm in size and are colored in light yellow tones. Caterpillars, growing up to 20 - 25 mm in length, have 22 legs each, and their transverse-baggy body, characterized by the absence of bristles and thorns, is painted in dirty green shades. On the sides and backs of the parasites there are transverse stripes of bluish-brown color. And the yellowish-white pupae grow up to 7 - 8 mm and are placed in brownish cocoons with a cylindrical shape.

Wintering of harmful larvae that have finished feeding takes place in the soil in cocoons. The depth of their occurrence in this case is from seven to fifteen centimeters. Rapeseed enemies pupate, as a rule, in April. After 8 - 15 days, adults begin to fly out, the additional food of which is the flowers of umbrella and cabbage crops. Mating females, using serrated ovipositors, quickly file the epidermis along the veins on the lower sides of the leaves and place one egg inside the resulting incisions. It is not at all difficult to notice places with laid eggs - they are given out by small swellings on the leaf blades. The total fertility of females reaches two hundred fifty-three hundred eggs. Rape sawflies stop their years and lay eggs in rainy and fairly cool weather. And in the case of prolonged bad weather, the parasites quickly die, without having time to lay eggs. When warm weather is established, after 6-11 days, harmful larvae hatch from the laid eggs, immediately starting active feeding.

The duration of caterpillar development is directly influenced by weather conditions. Typically, this process takes twenty-five to forty days. During this time, each caterpillar manages to pass six centuries. Gluttonous larvae eat leaves, leaving only thick veins from them. And on mustard, in addition to leaves, caterpillars also damage flowers with ovaries, as well as unripe fruits. Some time later, the pests pupate, and after nine or fourteen days it is already possible to observe the emergence of the imago of the next, second generation. And in Crimea, in some years, sometimes the third generation of pests can also develop. By the way, a small part of the voracious larvae can enter a state of diapause until the next spring.

How to fight

Weed control and deep autumn plowing of the soil are good preventive measures against rapeseed sawflies. But it will be advisable to treat growing crops with insecticides only if there are from three to five caterpillars per plant. During the period of mass hatching of caterpillars, it is recommended to treat the vegetation with the preparations "Actellik" or "Karate Zeon". Such biological preparations as "Entobacterin", "Lepidocid" and "Dendrobacillin" also give a good effect.

Endoparasites with ectoparasites play an important role in the destruction of the rape sawfly population. Also, the larvae of these bright villains are often parasitized by predatory tahini flies.