Robert from Hesperia writes
Weeping willow to fight flat headed borer
Onslaught Insecticide would be applied as a full coverage foliar spray applying to the point of drip but not run off as directed on the product label for the listed borers only. Bayer Advanced 12 Month Tree & Shrub Insect Control Landscape Formula can be applied to any non-edible trees for soft and flat headed borers and would be a better option for it’s systemic properties before the insects become an issue.
Answer last updated on: 11/13/2018