How to treat woodworm
Before chemically treating be clear you have an active infection and not a historical issue that has been treated in the past or that the moisture content of the timber is below 12% and humidity is under control in which case there will probably be no need apply a chemical treatment.
If you do decide to apply a DIY application the best chemical treatment is an HSE registered Boron applied by a low course pressure sprayer. The common alternative is a Microemulsion water based concentrate diluted with water. All applications should be carried out in accordance with the manufacturers data sheets and all PPE clothing especially face mask and goggles are worn.
Most importantly is the ongoing importance of keeping the timbers dry and ventilated.