Barberry Recurring Infestation: Overwintering Pest Control with Horticultural Oil

Barberries in New Jersey losing leaves and showing debris annually—spreading plant to plant but only on barberries—suggest barberry aphid, barberry webworm, or scale. All overwinter as eggs or adults on the plants.

Critical treatment: spray horticultural oil thoroughly in late winter/early spring (March) before bud break, coating interior branches and leaf undersides. This suffocates overwintering stages. Repeat in 2 weeks. Use dormant rate per label.

Monitor during growing season. Aphids cluster on new growth—spray insecticidal soap. Webworms make loose webs—prune out. Scale appears as bumps—oil or systemic.

Barberries are tough. Annual dormant oil spray breaks the cycle. Clean up leaf litter in fall to reduce overwintering sites.