Invasion Genetics of the Horse-Chestnut Leaf Miner, <i>Cameraria ohridella</i> (Lepidoptera: Gracillariidae), in European Russia: A Case of Successful Involvement of Citizen Science in Studying an Alien Insect Pest

Based on the intensive monitoring conducted by our team and volunteers in 2021, the secondary range of an alien horse-chestnut leaf miner, Cameraria ohridella Deschka & Dimić, 1986 (Lepidoptera: Gracillariidae), was specified in European Russia. This invasive pest was confirmed in 24 out of 58 administrative regions of Russia, which it has occupied for approximately 16 years. Analysis of the COI mtDNA gene sequenced in 201 specimens collected in 21 regions of the European part of Russia indicates the occurrence of two haplotypes (A and B), which are also present in the secondary range of C. ohridella in Eastern and Western Europe. The haplotype A dominated and was present in 87.5% of specimens from European Russia. In 2021, C. ohridella produced spectacular outbreaks in Aesculus hippocastanum in southern Russia, where it damaged more than 50% of the leaves in trees in 24 out of 30 distant localities. In the south of the country, the pest infested Acer pseudoplatanus, whereas other species of Acer of European, East Asian, and North American origin showed no signs of attacks. Taking into account that Ae. hippocastanum is present in most regions of European Russia, we expect a further range expansion of C. ohridella up to the Ural Mountains