Oak leaflet - the enemy of green oak forests

Oak is known for its power and longevity, its average height is 35 m, diameter - about a meter. But a tree with a huge crown and a strong trunk can be damaged by a small greenish moth. This is an oak leaflet, its voracious larvae eating leaves buds. With mass reproduction, pests completely expose the crown of the tree. Leafworm lives in the European part of Russia, Crimea, and the Caucasus. Comprehensive measures have been developed to control insects, including surveillance, the use of entomophages and chemicals.

View description

The green oak leaflet is a forest pest, a monophage that destroys oak foliage. They appear wherever there is a feed base. In the south of the habitat, protracted breeding outbreaks occur, causing significant damage to forestry. The family of leaflets includes about 10 thousand species. A characteristic feature is the folding of the eaten leaves into a tube. Caterpillars pull together their cobwebs and hide inside.

The Tortrixviridana species is represented by butterflies with a wingspan of 18-23 mm. Fore wings are green or yellow-green. Along the outer edge is a gray fringe. Hind wings plain, gray, fringe several tones lighter. Males and females look the same, females are larger.

Distribution area

Oak leaflet is found in Europe, Iran, Israel, Asia Minor, and northern Africa. In the Russian Federation it is noted in the oak forests of the Crimea, the Caucasus and the European region.

Reproduction and development

Adults appear in May-June. They are heat-loving, fly at a day temperature above + 17 ° C. On cool days they are not active, hiding among the leaves. Night hours are spent on tree branches, bushes and grass. Mating takes place in June. The fertilized female lays 2-3 eggs on the thickening between the branches, in the bumps and bumps. Egg size is less than 1 mm. The number of masonry is 50-60 pieces. The pest goes through a two-year development. One generation is replaced per year. After laying, the female dies.

Information. From above, the eggs are covered with female secretions that harden and darken in the air. The brown color of the shield makes it difficult to detect masonry.

The eggs are left to hibernate. In severe frosts, when the temperature drops below -25 ° C, the development of embryos stops, diapause begins. In spring, rounded greenish eggs darken. In April, caterpillars appear from them. The appearance of young growth coincides with the swelling of oak buds. Caterpillars climb into the kidneys and eat the contents. Inside the shelter they are protected from predators, so a large number of leafworm larvae survive.

Weather exposure

In cold spring, the exit of caterpillars from eggs is delayed. By their appearance, the buds are already blooming, turning into leaves. For larvae of the first age, this is rough food. They eat poorly, the number of surviving offspring is reduced. An early thaw is no less destructive. Caterpillars emerge from the shell, and the kidneys are still covered with hard scales. Weak jaws of insects are not able to gnaw a stroke and they die from hunger. Caterpillars easily tolerate spring frosts, but the cold destroys young leaves. The amount of food decreases, its chemical composition changes. These factors act negatively on the larvae.They begin to hurt, become vulnerable to all viruses and infections.

Leafworm Caterpillar

The body covers of the young caterpillar are gray-green. Head and chest legs are black. Under favorable conditions, it develops in 18-25 days. Before pupation, 5 ages and 4 molt pass. Adult caterpillars grow to 17-18 mm. Typical coloration is light green with a brown head and a visor.
On the body are many black warts and long blond hairs. There are claws on the chest and abdominal legs. The development of the caterpillar is on schedule:

• The first age is 4 days, spends inside the oak kidney.
• The second age is 2-3 days, moves to the leaf, eats the top and edges.
• The third age is 3 days, the larva is wrapped in a leaf, it bends the edge of the leaf plate and secures it with a web.
• The fourth age - 5 days, continues to eat leaf.
• Fifth, last age - takes about a week. Food stops, pupation begins.

Information. The disturbed caterpillar falls from the leaf, but it does not fly to the ground, but descends to the cobwebs to the lower branch.

Brown pupa, length 8-10 mm. The cocoon has a wide protrusion and 8 bristles. The doll lies in a web bag, one edge of which is open. The flight of adults stretched from June to July.

Malware

Caterpillars of the green leafworm eat up a large number of green leaves, starting from the top of the tree. Damage leads to a reduction in acorns. Leafless areas are often attacked by powdery mildew. With massive outbreaks of reproduction, the pest completely destroys the foliage. Trees growing on dry soils cannot regenerate and die. Outbreaks are periodic, but protracted, lasting up to 8 years. In the forest-steppe foci occur in well-heated areas of mixed forests and parks. In the steppe –– on old seasoned oak forests, massifs with sparse filling.

Methods of struggle

Only caterpillars of the oak leaflet have a negative impact on forest and park plantations; adults do not feed. To combat pest, special measures and preventive supervision have been developed.

Agrotechnical events

• Bookmark plantings with a priority choice of late oak forms.
• Planting mixed, tightly closed parks and forests.
• The formation of a dense layer of shrubs.
• In the home garden, the leaflets are collected manually, sticky hunting belts are installed on the trees.

Use of Entomophages

The oak leaflet has many natural enemies, including birds and insects. The construction of starling houses attracts the best caterpillar exterminator. Among the parasites and predators that limit the amount of the pest:

• ants
• ground beetles;
• tahins - flies infecting caterpillars with their eggs;
• pteromalids - parasite riders from the suborder of stalked bellied;
• Braconids - small and medium-sized riders, ectoparasites.

Information. About 100 species of entomophages parasitize on the larvae and pupae of the oak pest.

Chemicals

With severe infection, the destruction of the oak leafworm is possible only with the use of treatment with insecticides or biological pesticides. The procedure is performed at the time of opening of the oak buds. Spraying is performed on the crown in the morning or evening hours. Kinmix, Karbofos and Lepidocide preparations are used.

Prevention

Prevention measures for the green oak leaflet include removing bark from the trees where it was seen in the summer. Plant material is burned. The work is carried out in autumn. In winter, the pest eggs will be left without shelter and freeze. Prevention includes egg and adult surveillance. This procedure is time consuming, especially when searching for masonry. Butterflies are collected for counting using light traps. After a winter with low temperatures, wintering masonries are counted so as not to spend extra money on processing.