The Ubiquitous Apple Stoat Moth

2024 Author: Gavin MacAdam | [email protected]. Last modified: 2023-12-16 13:38

The apple stoat moth is almost ubiquitous and attacks apple trees very actively. The trees damaged by pests look from afar, as if they were burned by fire. The amount of harvest on them is significantly reduced, however, like its quality, the process of laying fruit buds is noticeably disrupted, and the growth of shoots is greatly reduced. Despite the fact that the generation of this moth is one year old, it manages to cause enormous harm

Meet the pest

The apple stoat moth is a rather attractive butterfly, whose wingspan can range from 17 to 22 mm. The white front wings of the pests are arranged in three lines and are equipped with 12 - 16 black dots, and the gray hind wings are framed with a long fringe.

Eggs of pests, reaching 0.3 mm in size, are rounded and slightly flattened. Initially they are yellowish, and after a while they become yellowish-brown. Caterpillars, growing in length up to 15 - 18 mm, are painted in gray tones. On their backs are two longitudinal rows of hairy little black warts. The legs, as well as the anal and chest plates of the caterpillars are painted black. The size of the pupae ranges from 12 to 14 mm. At first they are orange-yellow, and after some time they turn yellow-green. Wings of pupae are light brown, and cremasters equipped with six bristles are always dark brown. Their little white cocoons are combined into compact packs of several tens or even hundreds of pieces at once.

Caterpillars of the first instar overwinter under shields. As soon as with the onset of spring heat, the average daily temperature reaches twelve degrees, five days after the beginning of bud opening, the malevolent caterpillars get out from under the shields and instantly penetrate under the epidermis of young leaves and deep into the buds. For about 9 - 12 days, they feed on the epidermis in the mines they form. At the end of the first molt, which coincides with the time of flowering of apple trees, caterpillars leave mines and move to leaf surfaces, where they begin to skeletonize leaves and weave spider nests. All caterpillars, gnawing the leaves, gradually move from the tops of the branches to their bases, braiding them with a rather dense cobweb. The average duration of feeding of caterpillars is from forty to forty-five days - this period includes the time of their stay in leaf mines. In addition, during this time they manage to go through five ages. Hot and dry weather is especially favorable for their development, but wet and cool weather contributes significantly to their increased mortality.

The caterpillars that have completed their development slowly slide into groups, placing their chairmen up next to each other. Here they form cocoons, in which they later pupate. Nine to fourteen days after pupation, butterflies appear, flying mainly in the evenings. Their years lasts for about thirty to forty days, until the last decade of August. Twelve to sixteen days after the release, the butterflies mate, and another five days later they begin to lay eggs. Their total fertility at the same time reaches ninety - one hundred eggs. Eggs are laid by females on shoots and on smooth bark in groups of fifteen to thirty pieces each. At the same time, the females place them in tiles and cover each clutch with unpleasant mucus, which gradually solidifies, forming small shields from 4 to 7 mm. Initially, such shields are characterized by a reddish color, and after twenty to thirty days they become grayish-brown, approaching in color to the color of the tree bark.

A day, nine to fifteen after the laying of eggs, a revival of gluttonous caterpillars is observed. First, for eight to ten days, they scrape the bark under the shields and feed on the shells of eggs, and after this time they enter diapause until the next spring.

How to fight

During the period of mass emergence of caterpillars of the apple ermine moth from under the shields (as a rule, it falls on the stage of bud separation), fruit trees begin to be sprayed with systemic insecticides. And when the apple trees have faded, you can start treating with suitable biological products or inhibitors of chitin synthesis.

The apple stoat moth also has a lot of natural enemies - about a hundred different parasites were noticed on pests, infecting about 60% of individuals. The eggs of the ubiquitous villains are parasitized by poachers, and tahina flies and gluttonous ichneumonids feast on caterpillars.