The pear psylla, Cacopsylla pyri, is a widely distributed pest of pear in central Europe and can inflict serious damage in pear orchards.
Pear psylla feeding leads to growth inhibition and malformation of leaves and fruits. Heavy infestations can cause premature leaf fall and fruit drop. Flowers attacked by first generation nymphs turn brown and die. Feeding later in the season may affect the harvest of the next year by weakening or killing fruit buds.
Pear psyllas excrete large amounts of honeydew. Sooty moulds often grow on the honeydew covering shoots, leaves and developing fruits with a sticky black layer.
Adults pear psyllas are 2-3 mm long and orange red to blackish. They have white, longitudinal stripes on the back of the thorax. Their forewings are clear with dark veins. The eggs are oval, approximately 0.3 mm long and yellowish orange in colour. The nymphs are initially yellowish with clearly visible purplish-red eyes. Later instars are purplish to reddish brown with whitish longitudinal stripes and blackish markings on the head and body.
Pear psyllas overwinter as adults, sheltering on the bark of pear trees. The adults become active in spring and start to feed on young leaves and flowers. Eggs are deposited in crevices of the bark of twigs and hatch after about 3 weeks. There are 5 nymphal instars which feed on twigs and shoots. Depending on the temperature, there are 3 or more generations per year. Overwintering adults are produced in November or December.