Effective Aphid Control on Mature Birch Trees

Four mature birches in SF Bay area produce heavy honeydew drips from aphids. Missed dormant spray window; considering malathion, hose washing, or systemic treatment.

Why Contact Sprays Fail

Malathion must hit every aphid—impossible on large trees. Survivors rebound rapidly.

Systemic Solutions

1. Bayer Advanced Tree & Shrub Insect Control (soil drench): Roots absorb, translocate to leaves. One application lasts season. Takes 2-3 weeks to work.
2. Orthene foliar spray: Also systemic, faster action but requires thorough coverage (both leaf sides, stems). Needs 2+ applications.

For large trees, soil drench is most practical. Available at local nurseries.