Does Penetreat kill mildew?
No. Mildew is a type of fungi that exists on the surface of wood and does not actually attack or eat wood (although it can cause some discoloration of the wood surface). Penetreat’s great strength is its ability to control wood-destroying fungi that actually cause rot. Of course, Penetreat also helps to control many insects, which are killed when they ingest the treated wood. If you want to control mildew, you should use an additional mildewcide in your stain and clear coat. Sashco recommends Stay Clean I/E by Walla Walla Environmental, available through Sashco distributors.