The horse-chestnut tree (Aesculus hippocastanum L.: Hippocastanaceae) is native to temperate part of Northern hemisphere mostly in Balkan, Caucasus, Asia Minor, and Himalayas. Closely related trees of Aesculus genus are widespread in Northern America (A. pavia, A. glabra, A. parviflora etc.). Horse-chestnut is a decorative tree of urban parks, recreation areas and public gardens since the second half of 17th Century. Fig. 1: Horse chestnut leaves infested by C. ohridella (early stage) Recently, this common tree is endangered by the horse-chestnut leafminer, Cameraria ohridella (Lepidoptera: Gracillariidae). Larvae of this tiny moth destroy chestnut leaves' parenchyma forming large mines (Fig. 1) in which they pupate. The miner may have up to 4 generations per year with exponential generation to generation growth rate (Skuhravý, 1998). The almost total absence of natural enemies (larval paratization is only ca 5-15%, max. 21%; Grabenweger and Lethmayer, 1999) is, most likely, the major cause of its large scale outbreak (Skuhravý, 1998). If the infested trees are defoliated in the middle of their vegetative season, they are not able to accumulate enough reserves for winter and next spring. to Cameraria main page MH © 10.IX.2002