Hessian Fly

Hessian Fly

Pest Type: Cereal Pest

Row: Diptera-Diptera

Family: Gall midges-Cecidomyiidae

Distributed everywhere except in mountainous areas, often causes damage in the steppe. Outwardly resembles a small mosquito, with dark gray or brown color. In females, the abdomen is often with a reddish tinge. Body length is 2.5-3.5 mm. The eggs are oval, shiny, 0.5 mm long. Only laid eggs are transparent, with orange spots, and subsequently, become dark.

The larva of the first age is worm-shaped, red-yellow, up to 1 mm long, the other is spindle-shaped, milky white or greenish, 4-5 mm.

Larvae overwinter on the stairs of winter crops, carrion droppings, wheatgrass. Larvae that did not manage to complete their development and form puparia are very sensitive to low temperature, and usually, die in cold winters.

Pupation occurs in spring. The departure of flies is stretched and uneven, begins after a steady establishment of the average daily air temperature of 10-12 ° C. The calendar terms for summer flies usually occur in the second half of April-May, phenological ones at the end of tillering are the first half of the winter phase. Unlike the Swedish flies, the Hessian after mating, mates and is able to lay eggs without additional food if the maximum air temperature reaches 14-16 ° C.

The female lives 2-7 days and during this time lays 46-500 eggs, an average of 180, placing them in a chain of several pieces mainly from the upper side of the leaf blade of winter and spring crops.

Embryonic development lasts 4-8 days. Eggs and young larvae are very sensitive to high temperatures and low relative humidity. After rebirth, the larvae move along the puff plate to its base, where they penetrate beyond the sheath of the leaf and feed on the stalk juices. In spring crops, they are usually at the foot of the shoot, inhibiting the growth and development of plants. This leads to their death, which is more often observed in spring dry conditions. On winter crops, characteristic knees form in the period of entry into the tube — in damaged plants, since the stalk becomes thinner at the feeding place of the larvae. Therefore, heavily damaged crops take the form of a battered hail or ceiling. A similar pattern is observed in spring crops damaged by second-generation larvae of the Hessian fly. On one stalk develops 1-4.

Having completed the development, they, without leaving the vagina of the leaf, pupate. The second generation flies at the time of earing, the formation of grain and populates mainly spring ear crops. At this time, in hot, dry weather, a significant part of the larvae falls into diapause, which lasts until the end of summer. In the conditions of a moderately warm rainy summer in the southern regions of Russia, according to many researchers, 4-5 generations of the Hessian fly, in particular, 2-3 summer ones, develop. This pest damages winter wheat, as well as barley and rye.

Protective measures. Compliance with crop rotation, isolation of spring crops from winter crops, optimal planting dates for the zone, cultivation of varieties that are relatively resistant to stem pests, including the Hessian fly. Stubble peeling, early deep autumn plowing, destruction of wheatgrass foci. Chemical treatments are recommended only in the centers of mass reproduction or, if necessary, the protection of, especially valuable crops. If the economic threshold of harmfulness is exceeded during the germination period, tillering in the presence of 30-50 flies per 100 sweeps of a net or 5-10% of damaged stems at the beginning of a mass summer of flies.