Biology: Overwinter as adults outside the orchard and move in to lay eggs on buds and twigs in early spring. The adults resemble small cicadas.
Symptoms: Honeydew; leaf scorching; leaf drop; black sooty mold on leaves and fruit. Pear psylla may also transmit a disease called “pear decline” that can slowly kill trees over a number of years.
Monitoring: Look for psylla adults early in the spring (starting 6 weeks before bloom) by tapping or shaking the branches over a light colored beating tray.
Treatment Threshold: Early season, 0.5 nymphs/leaf; summer, 1.5 nymphs/leaf; examine 10 leaves per 5 randomly selected trees/block.
Degree Day Model:
- Lower threshold: 41°F
Management Considerations: Root stocks resistant to pear decline are available. Resistance to many insecticides has occurred in pear psylla populations, so switching insecticides across years can help prevent resistance in your orchard. The best control is achieved with a dormant spray to kill overwintered adults before new eggs are laid.