2024 Author: Gavin MacAdam | [email protected]. Last modified: 2023-12-16 13:38
The bunchy grape leafworm lives almost everywhere where there are vineyards. She especially actively harms them in the southern regions of Russia. The berries damaged by this parasite either dry up or rot, and along with these destructive processes, the last hopes for a plentiful excellent harvest are fading away
Meet the pest
The bunchy grape leafworm is a butterfly, the wingspan of which reaches about 11 - 13 mm. Its front brownish-olive wings are equipped with a rather wide band in yellow-white tones and a large speck at the inner corner, and are also dotted with dark strokes. The hind wings of this pest are grayish, dark to the brim.
The size of the flattened yellowish eggs of the pests is 0.5-0.6 mm, and the length of the green-olive caterpillars ranges from 10 to 12 mm. The chair of the caterpillars is light brown, and the thoracic legs, as well as the prothoracic scutellum, are brown. Pupae, yellow-brown with a slight greenish tint, reach 5 - 6 mm in size. The tips of their abdomens are yellowish, and on the last segment there are eight hook-like reddish setae.
Pupae wintering takes place in white rather silky cocoons in dry grape clusters, cracked bark, fallen leaves, cracks in wooden posts, etc. As soon as the average daily temperature reaches fourteen degrees, the spring flight of harmful butterflies starts. In the steppe zone, this usually occurs in May, and on the southern coast of Crimea, butterflies can be seen already at the end of the second decade of April. Meanwhile, the flight of butterflies can stretch up to twenty to thirty days, if the spring is relatively cool. Mostly butterfly years are celebrated at dawn and in the evenings, a little less often in the daytime in cloudy weather.
Additional food for harmful butterflies is sweet secretions and flower nectar. After departure, on the fifth or sixth day, the pests lay eggs on inflorescences, flowers and buds - both in small groups and individually. Their total fertility is on average from sixty to one hundred eggs.
The best temperature for the development of a bunchy grape leaf roll is 15 - 30 degrees. In this case, the relative humidity should be above fifty percent. If the air humidity is lower and the air temperature exceeds 32 degrees, the laid eggs die en masse and the fertility of the female parasites is sharply reduced. The duration of the embryonic development of the first generation is about nine to ten days, and the second and third - from five to seven days. The reborn small caterpillars of the first generation feed mainly on flower buds, damaging the stamens and pistils of flowers. After the first molt, having managed to damage a couple of buds, harmful caterpillars weave spider tubes and, staying in them, damage more and more buds. At the hour of its development, one individual is capable of damaging up to forty to sixty buds. Caterpillars develop for 23 - 28 days, and then they pupate in folded edges of leaves fastened with tiny silks.
Ten to twelve days later, butterflies of the second generation fly out, laying eggs directly on the green berries. Until the first molt, they live quite openly, gnawing out small numerous depressions on the surfaces of the berries. And then they go inside them, gnawing cavities in the forming pulp. At the end of each molt, the parasites move to neighboring berries. But their pupation occurs mainly on the leaves, much less often among the damaged berries. Butterflies of the third generation that fly out after seven to eight days lay their eggs on ripe berries one at a time - subsequently, caterpillars will penetrate into these berries and start feeding there. Each caterpillar of the second and third generation is capable of damaging about four to eight berries. And when it comes time to harvest, the caterpillars move to wintering places and then pupate there.
How to fight
Spiders, carnivorous thrips, ground beetles, sirphid flies, coccinelids and predatory bugs are actively involved in the destruction of the bunchy grape leafworm. And on pupae with caterpillars, more than sixty varieties of various endoparasites can parasitize: larvae of tahin flies, riders from the ichneumonid family, as well as representatives of the numerous braconid family.
Pheromone traps are also a good method of dealing with this pest. And if with their help it is possible to identify more than a dozen butterflies in each in five days, it is advisable to start treating the vineyards with insecticides or biological products. Flufenoxuron, Parathion, Sevin, Fozalon, Tsidial, Ekamet, Sumicidin, Tsimbush, Tokution and a number of others have proven themselves well.
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