Unusual phenomenon – a new birch pest

It was found this spring in one of the garden plots in the Zagoryansky Village of the Moscow Region. Suddenly all the birch trunk has covered with dense spider web. It gave cause for the plot owners for concern for the birch’s future, and at the beginning of August they requested the Russian Research Institute for Silviculture and Mechanization of Forestry (VNIILM) to help them to determine the cause of such an abundant web.

For the purpose of birch inspection the research scientist of the Center for the Selected Biotechnologies for Forest Protection of VNIILM, the head of the Laboratory of Forest Protection from Invasive and Quarantine Organisms Yu.I. Gninenko was sent on a business trip. As a result of examinations, he made the following conclusion: “The cause of the dense web is the activity of the core birch moth Argyresthia goedartella. Typically, this insect is quite rare, but in 2016 the moth dramatically increased in its number. So, such web-wrapped birches meet this summer in many districts of the Moscow Region, as well as in Ivanovo Region, Vladimir Region and others”.

In early spring, when trees just begin to awake, the caterpillars of the birch moth feed and develop inside of the catkins of birch and alder. In April, the feeding comes to an end and they move to the trunks, paving their way with a web, where they pupate in cracks in the thick bark. When there are a lot of caterpillars, they can cover the entire trunk with quite dense spider web. According to Yu.Gninenko, the very appearance of this web is not dangerous for the tree, as well as the damages that caterpillars cause to the catkins. Although such catkins die and do not produce seeds, it is not critical for the tree. The caterpillars cannot damage the foliage or trunk. Thus, the birch moth causes the visual damage, disrupting the appearance of the plant, but not causing the significant harm to the tree.

On the territory of the Tatarstan’s forest reserve no such pest is found. For Tatarstan, the damages of plantations caused by gypsy moth, pea-green oak and oak red-barred twist are typical. The Tatarstan forestry experts work out measures aimed at early detection, localization and elimination of foci of these types of pests.