Lesser Peachtree Borer on Weeping Cherry: Diagnosis and Management

A weeping cherry bleeding sap (gummosis) from the trunk after Japanese beetle infestation and frequent pruning is likely attacked by the lesser peachtree borer (Synanthedon pictipes). This clear-wing moth larva tunnels in the cambium of stone fruits (cherry, peach, plum), especially at wound sites from pruning, winter injury, or mechanical damage.

Key Symptoms

• Gum (sap) oozing from trunk/branches, often mixed with reddish-brown frass (sawdust-like excrement).
• Bark peeling off damaged areas.
• Empty brown pupal cases protruding from exit holes.
• Branch girdling and dieback.
• Adult moths: wasp-like, dark blue with yellow bands, clear wings; fly daytime (10 AM–2 PM).

Life Cycle & Timing

• Overwinter as larvae under bark.
• Pupate in spring; adults emerge May–September (two generations).
• Eggs laid in bark crevices near wounds.
• Larvae hatch in 8–10 days, bore into cambium.

Control Strategy

Prevention is critical: Once larvae are under bark, sprays are ineffective.

• Pheromone traps monitor male flight to time sprays.
• Trunk/spray applications 7–14 days after first moth catch (covers egg hatch).
• Second spray at peak second-generation flight (early September).

Labeled insecticides (professional/restricted use): Asana XL, Ambush, Lorsban, Pounce, Thiodan. Must be applied as directed trunk/scaffold drench to 8 ft.

Homeowner option: Imidacloprid (Bayer Advanced Tree & Shrub) soil drench. Systemic uptake provides some control of flatheaded borers (like this species) but results are inconsistent. Best applied early spring.

Cultural Practices

• Minimize pruning wounds during moth flight (May–Sept).
• Prune in late winter (dormant season).
• Protect trunk from mechanical injury.
• Maintain tree vigor with water/fertilizer.

Due to pesticide restrictions and application difficulty, a certified arborist is recommended for confirmation and treatment. Early intervention saves the tree.