Consequences of the Outbreaks of the Poplar Leaf Miner and Other Mining Microlepidoptera in St. Petersburg

The poplar leaf miner Phyllonorycter populifoliella , a well-known pest from the Gracillariidae family, was first recorded in St. Petersburg in the middle of the last century. This species had its first outbreak in 1991–1999, followed by death of a significant part of poplars in the city and suburbs. Despite the prominence of this pest group, there are limited data on the effect on the host-plant state from mining-insect damage to the trees’ assimilation apparatuses. The changes in the radial growth of the Berlin poplar Populus × berolinensis (70–80 years), which was intensely damaged during the outbreak, and the white poplar Populus alba (the average age is 100 years) were compared, and the damage to the latter was much less severe. The growth of white poplar slightly decreased during the outbreak (1991–1998), from 4.79 mm (1942–1990) to 3.61 mm (1991–1998), and then quickly recovered to the initial values and up to 4.86 mm (1999–2018). The growth of the Berlin poplar over the same time periods fell sharply, from 6.29 to 2.45 and 1.80 mm, respectively. It was shown that the growth of Berlin poplar sharply decreased within 5–7 years from the beginning of the outbreak and that the low growth levels persisted afterwards. This indicated that there may be irreversible consequences for poplars in the case of prolonged and intense damage by mining pests. The significant impact of mining pests on the plantation state requires monitoring and measures to control the spread of pests of this group. The problem is further aggravated by the appearance of three species of invasive mining Lepidoptera, the lime leaf miner Ph. issikii , the horse-chestnut leaf miner Cameraria ohridella , and the leaf blotch miner moth Acrocercops brongniardella, on the territory of St. Petersburg and the surrounding territories.