Parasitism of Cameraria ohridella (Lepidoptera, Gracillariidae) in natural and artificial horse-chestnut stands in the Balkans.
The horse-chestnut leafminer, Cameraria ohridella Deschka & Dimic, was discovered during a mass outbreak on planted horse-chestnut trees, Aesculus hippocastanum, near Lake Ohrid in Macedonia. However, several peculiarities in the leafminer's biology and ecology, such as its inefficient control through natural enemies, indicate that it may be of exotic origin. In this study, the parasitism of C. ohridella was examined in natural and artificial horse-chestnut stands in South-eastern Europe. The size and composition of the parasitoid complex of natural stands was comparable with that known from artificial stands. No specialist parasitoid species were detected in any of the samples. The only parasitoid species found exclusively in natural stands during this investigation were the braconid Colastes braconius and the eulophid Chrysocharis phryne. Both are known to be polyphagous on many leafminers in Europe and C. braconius has been often recorded from C. ohridella in artificial stands in previous studies. Parasitism levels varied within the same range (3.6-21.0%) throughout the entire region, in both types of habitats. These results suggest that the parasitoid complex of C. ohridella in natural and planted horse-chestnut stands in Europe is typically that of an exotic, recently introduced leafminer. Consequently, C. ohridella is probably not indigenous in the Balkans, but has been introduced to the area of its discovery from another continent.