Q: Last week you said that no borer sprays are effective on borers in pines and oaks. How can garden centers sell insecticides labeled “Borer Spray” if they don’t work?

A: I have a hammer in my garage that I plan to label “Borer Hammer! 100% Effective! 100% Organic! Lifetime Guarantee!”.

All of my claims are true and I probably could get my hammer registered as a pest control device and sell it in garden centers. Purchasers, though, might have a hard time killing borers anywhere except on the surface of a tree. While my product might be 100% effective if the borer was exposed, it would be less practical once the borer tunneled into the tree.

After borers have penetrated under the bark of a tree, conventional garden insecticides can not reach them. Even if a product is labeled “Borer Spray”, it won’t kill borers unless it touches them.

Borer sprays do protect trees from borer invasion but in most cases the entire tree must be sprayed in order to achieve complete safety. That is not possible for most homeowners.

I stand by my previous advice: watering a tree does more to protect it from borers and is more practical in the long run