Type of pest: Pests of afforestation
Row: Lepidoptera – Lepidoptera
Family: Leaflet Tortricidae
It is found everywhere. Damaged oak is branched, especially its early form, as well as fluffy oak.
Butterfly with a wingspan of 18-23 mm; fore wings and chest green, hind wings, and abdomen gray. The egg is 0.7-0.8 mm in size, round, flattened, first light yellow, later gray-brown. Caterpillar 17-20 mm long, gray-green; the chairman is dark brown, prothoracic and anal scutes are brown or yellow-green, legs are black in December. Pupa – 9-11 mm, dark brown, cremaster with eight small hooked setae.
Fertilized eggs hibernate under shields on the bark of young branches. Embryonic development occurs in February thaws and in spring with a lower development threshold of 3.5 ° C. Caterpillars revive in late April – early May, during the swelling period of the early oak buds. Without food, caterpillars can withstand no more than 3-5 days. First, they bite into the swollen buds and feed on them until the leaves separate. With the leaves blooming, they damage it, loosely braiding the rosette with a cobweb. Later they pipe or live under the twisted edge of the sheet. First, they skeletonize, at an older age they eat leaves completely. The development of caterpillars lasts 19-25 days, passing 5 centuries. Before pupation, the caterpillar bends the edge of the leaf blade to the lower side, fixing its edges with a cobweb, and pupate in this shelter. The development of the pupa lasts 10-15 days. Before the butterfly leaves, the chrysalis extends outward. Years of butterflies, the population is stretched and lasts about two months (June – July). The female lays 2-3 eggs on the thickenings between the annual shoots, on the scars at the base of the leaf petioles, in the forks of the branches, near the buds and in other places where there are uneven barks, and covers them with a gray-brown shield from the secretions of the accessory genital glands.
Butterflies lay their eggs both on the early and late forms of oak, without giving preference to one of them. The stability of late oak forms is explained by the late development of buds and leaves. Caterpillars, reborn on late forms of oak, are not able to overcome the hard tissues of the kidneys and die of hunger. Fertility – 50-100 eggs. One generation develops per year.
The death of the pest is observed in winter when the temperature drops to -27 … -30 ° C, in spring, if the timing of the revival of the caterpillars does not coincide with the opening phase of the kidneys, and in the summer (July, August), in dry and hot weather, which causes the drying of laid eggs.
Eggs infect various egg-eaters. On caterpillars and pupae, more than 90 species of entomophagous parasitize. Caterpillars are infected by ichneumonids, acids, and ichneumonids, chalcids, etc. develop in the chrysalis. Forest ants, ground beetles, carnivores, carnivores – birds, especially starlings, feed on caterpillars of the green oak leaflet. In wet years, the death of the pest from bacterial, fungal and viral diseases is observed. Buds, oak leaves and other hardwoods damage many other types of leafworms.
Protective measures. When laying field-protective forest stands, late oak should be preferred. The attraction of insectivorous birds to the plantations. With a population of more than 0.5 egg laying on 1m branches, it is necessary to use a biological product or an insecticide at the beginning of the mass revival of caterpillars.