Weeping Cherry Borer Infestation: Identification and Spinosad Treatment

A 20-year-old weeping cherry in Victoria, Australia, suddenly declined. Trunk shows a large hole with paper-thin wood and tiny internal holes. No visible insects. Owner asks if the tree is savable and if a nearby cherry is at risk.

Diagnosis: Borers

Two borer types attack Prunus:

• Longhorn beetles (Cerambycidae): large, long antennae.
• Clearwing moths (Sesiidae): wasp-like, striped, clear wings.

Larvae tunnel unseen; damage (sawdust, sap, dead limbs) is the only sign.

Action Plan

1. Prune out all dead wood and loose bark.
2. Clean leaf litter around both trees.
3. Spray trunks and canopies thoroughly with Spinosad (organic, translaminar). It kills only chewing/boring insects, sparing beneficials.
4. Probe sap-oozing holes with a thin wire to mechanically remove larvae (labor-intensive but effective).

No homemade remedy matches Spinosad for borers. Paint trunks white (base 2 ft) to deter future egg-laying.