Bora-Care is always the recommended product for treating active Powderpost Beetles because it penetrates deeper into the wood, up to 8 inches with 2 applications. Timbor will only go about 1/4 inch so it will not get to the larvae already in the wood. Bora-Care can take up to 30 days or more to penetrate all the way through a piece of wood and this will vary depending on how thick the wood is and the moisture content. We would recommend applying the Bora-Care and not a second application of Timbor. The larvae stage in the life of the Powderpost beetle is the longest, lasting from 1 to 10 years before it will mature to adulthood so it can take time to completely erradicate them.
Please take a moment to read over our article on How to Get Rid of Powderpost Beetles.