How do I treat wood borers in floorboards?

[Ross4]

I noticed a weak spot under the carpet in a bedroom. I crawled under the house to find one board has been almost completely eaten by borers, and they have partially eaten another one about 1m away. I'm not sure about using the chemicals suggested in the cramped space under the house. My house is 70 years old and all the other boards look fine. Will they spread into old timber like this? What should I do? 

[MitchellMc]

Welcome to the Bunnings Workshop community @Ross4. It's sensational to have you join us, and many thanks for your question about wood borer.

An active borer infestation in your floorboards is definitely a concern, especially in an older home. I’d strongly recommend contacting a pest control professional to assess and treat the problem. DIY products might help with surface-level issues, but they’re unlikely to reach into the timber effectively, especially in a confined space like under your house. Left untreated, borers can continue to spread and cause significant structural damage over time, even in older hardwoods that seem dense and resistant.

A professional will be able to confirm whether the infestation is still active, the extent of it, and what method—whether a targeted chemical treatment, timber replacement, or broader protective measures—is best for your situation. The sooner it’s addressed, the more chance you have of containing the damage.

Please let me know if you have any questions.

Mitchell