How to preserve horse chestnut trees from Cameraria ohridella in the urban environment

Control of Cameraria ohridella Deschka and Dimic (Lepidoptera: Gracillariidae), a pest on the horse chestnut tree (Aesculus hippocastanum L.) was tested using systemic injection in the 4-year period (2002–2005). Imidacloprid and abamectin were used with a single systemic tree injection treatment during May, immediately after blossom. A total of 77,760 leaves were sampled in the field to assess the effect on the number of mines caused by the horse chestnut leaf mining moth by comparing population levels in treated vs untreated trees. The mean number of mines per leaf ranged from 0 to 106.54.Both insecticides contained the pest, and their persistence was indicated by the level of effectives during the second year after treatment. The number of mines on the treated plants decreased significantly, and during the last year not more than three mines per leaf were observed, as against 64 mines on the control plants. Generally the infestation was reduced by up to 82%.Most of the holes in the bark of the treated plants were healed within 6–7 months from the treatment. Only in few trees extravasation of mucilaginous exudates or cracks on the trunk occurred.