Observations on the development of the horse chestnut leafminer on red horse chestnut (Aesculus x carnea H.) were carried out in Wrocław, Lower Silesia, Poland, in 2001–2003. Three generations of the pest were recorded to lay eggs on the red horse chestnut leaves. Although females of each generation deposited eggs abundantly, the hatching larvae died after a short period of feeding in the plant’s leaves and the species did not complete its development on this tree. Mostly L1 and L2 larvae were found inside the leaf mines. The observed leaf damage was, therefore, negligible.
Extract of Polyscias filicifolia suspension culture was used to reduce damage to horse chestnut (Aesculus hippocastanum) leaves by larvae of the horse chestnut leaf miner (Cameraria ohridella). The results showed the repellent effect of biomass extracts on Cameraria ohridella moths. The number of moths caught per day on sticky traps treated with extract was more than 50% lower than the control. The same extract on leaflets caused C. ohridella females to lay ~20% fewer eggs than on leaflets without extract. P. filicifolia extract had a repellent effect on female moths in laboratory conditions as well. Only single mines were observed on leaves treated with P. filicifolia extract, five times less than on control leaves. The data indicate that P. filicifolia extract can be used as a repellent for C. ohridella in springtime when the overwintering generation emerges from pupae.