Boxwood psyllid larva. Coloured scanning electron micrograph (SEM).The boxwood psyllid (Psylla buxi) is the most common insect pest of Buxus sempervirens but all boxwoods are susceptible. It causes damage by piercing and sucking sap from buds and young leaves resulting in a conspicuous cupping of the foliage. The psyllid nymphs will be visible inside the cupped leaves although the most obvious sign is the waxy filaments and secretions they produce. Magnification: x150 when printed at 10 centimetres wide.