The horse chestnut leafminer (Cameraria ohridella) is a species of moth, a pest that infests chestnut trees and has recently spread explosively throughout central Europe. It was first observed near lake Ohrid in Macedonia in 1984 and christened Cameraria ohridella in 1986. Since it is not hindered by specialized predators or parasites, the leafminer has spread quickly and once it reaches a region, it infests all horse chestnut (Aesculus hippocastanum) trees to a shocking degree. Red horse chestnut (Aesculus carnea) and red buckeye (Aesculus pavia) appear to be more resistant (or less favoured by the leafminer).

The moth's larvae live inside the tree leaves, eating through the tissue and creating small tunnels or "mines" (thus the name "leafminer"). After 3 to 4 weeks, the larvae spin cocoons from which new moths emerge. In a hot, dry summer, three or more such generation cycles can occur! This leads to such severe infestation that the damage results in complete defoliation of the trees in late summer. Even before that, the leaves turn brown and unsightly, which is the main problem, horse chestnuts being popular ornamental plants. Fortunately, the infestation does not appear to kill the trees, although it of course hinders their development. So far, no effective way to combat the leafminer has been found, although the yearly infestation can be delayed and reduced by removing all dead foliage from the vicinity of the trees, since the leafblighter uses it to hibernate during winter.

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