Grape Bunch Leaf

Grape Bunch Leaf

Pest Type: Grape Pest

Row: Lepidoptera – Lepidoptera

Family: leaflets – Tortricidae

It is found throughout industrial viticulture. Especially harmful in the southern regions of Russia.

Butterfly with a wingspan of 11-13 mm, front wings are brown-olive with a wide yellow-white band with dark strokes; at the inner corner is a large spot; hind wings gray, dark to the brim. Egg 0.5-0.6 mm in size, yellow, flattened. Caterpillar 10-12 mm long, green-olive, chairman light brown, prothoracic scutellum, and chest legs brown. Pupa 5–6 mm in size, yellow-brown with a greenish tint and yellow tip of the abdomen; in the last segment, eight red hook-shaped bristles.

Pupae overwinter in white silky cocoons in cracks of bark, crevices of wooden posts, in dry tassels of grapes, fallen leaves, and other places. Spring departure of butterflies begins with the onset of stable average daily temperatures of 14 ° C. On the southern coast of Crimea, this happens at the end of the second decade of April, in the steppe zone in May. In cool spring, the flight of butterflies stretches to 20-30 days. Years occur in the evening and at dawn, less often – in the afternoon, in cloudy weather.

Butterflies additionally feed on the nectar of flowers and sweet secretions. On the 5-6th day after the departure, the butterflies lay their eggs individually or in small groups on buds, flowers, and inflorescences. Fertility – 60-100 eggs.

The optimal conditions for the pest are a temperature of 15-30 ° C and relative humidity of more than 50%. At temperatures above 32 ° C and relative humidity below 50%, the fertility of butterflies decreases sharply, and the mass death of laid eggs is also observed.

Embryonic development of the first generation lasts 9-10 days, of the second and third – 5-7 days. Having revived, the first generation caterpillars feed on buds, damaging also the pistil and stamens of flowers. After the first molt, having damaged 2-3 buds, the caterpillars weave a spider web and those in it, damaging more and more buds. One caterpillar per hour of its development damages 40-60 buds. Caterpillars develop for 23-28 days, after which they pupate in the folded edges of the leaves fastened with silk.

After 10-12 days, butterflies of the second generation fly out, which lay eggs on green berries. Until the first molt, the caterpillars live openly, gnawing small depressions on the surface of the berries. Then they penetrate inside and gnaw cavities in the pulp. After each molt, the caterpillars pass into the neighboring berry. Pupation on leaves, less often among damaged berries. Butterflies of the third generation, which fly out after 7-8 days, lay their eggs one at a time on ripe berries, into which they penetrate and feed on the caterpillars. One 2-3th generation caterpillar damages 4 to 8 berries. By the time of harvest, the caterpillars move to winter places and pupate there. Damaged berries either dry up or rot.

The leafworm is destroyed by ground beetles, carnivorous bugs, gold flies, coccinellids, sirfida flies, carnivorous thrips, spiders.

More than 60 species of endoparasites parasitize caterpillars and pupae: horsemen from the Ichneumonidae family, many species from the braconid family, larvae of the flies, etc.

Protective measures. The economic threshold for harmfulness is a catch in 5 days of more than 10 butterflies with pheromone traps, for the first generation – dessert varieties – 3-5; wine varieties – 8-10 caterpillars / 100 brushes, for the second – dessert varieties – 4-9, wine varieties – 8-12 caterpillars / 100 brushes, for the third – dessert varieties – 5-9, wine varieties – 6-12 caterpillars / 100 berries. If economic thresholds are exceeded – treatment with biological products or insecticides.

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