Diagnosing Frothy Flux and Borer Damage in Globe Willow

What You're Seeing

A globe willow exuding a white, sour-smelling fluid that attracts flies, with grubs under the bark, indicates two issues: frothy flux (a yeast-driven fermentation of sap from wounds) and wood borers creating entry points.

Treatment Plan

1. Borer control: Purchase a bark-applied borer insecticide (e.g., permethrin or bifenthrin) from a local garden center. Spray the trunk and major branches according to label directions to kill larvae and deter adults.
2. Frothy flux management: No direct cure exists. Focus on tree health: water deeply during drought, mulch properly, and avoid further bark injury. The fermentation usually subsides once the wound calluses over.
3. Sanitation: Remove any dead or severely damaged limbs to reduce stress.

Prevention

Healthy, vigorous willows are less susceptible to both problems. Annual fertilization with a balanced fertilizer (e.g., 10-10-10) in early spring supports recovery.

Reference

Colorado State University Extension provides detailed information on frothy flux and borers: PlantTalk Colorado.