Extensive browning and falling of leaves of the horse chestnut (Aesculus hippocastanum) as early as in July and subsequent tree death is caused by the horse chestnut leaf-miner (cameraria ohridella) - an urban pest. The condition of trees in cities, not only the horse chestnut, is also affected significantly by other conditions: soil environment, its chemical and physical properties, water saturation, aeration or urban development.