Fence woods, such as pine, cedar and locust, are known for their durability, practicality and long lifespan. They are not, however, necessarily resistant to mildew growth. Wood located in damp, humid areas surrounded by dense vegetation is especially prone to mildew spores. Besides creating green stains, mildew eats dirt and organic debris accumulated on wood and causes structures to deteriorate over time. Promptly remove green mildew from fence wood to preserve the structure's appearance and longevity.
Remove any peeling or flaking paint from the wood, if applicable, using a paint scraper. Mildew can thrive underneath loose paint, as well as on exposed wood.
Wet any plants, shrubs and grass near the fence wood with water to protect them from the trisodium phosphate runoff.
Fill a bucket with 1 gallon of warm water. While wearing rubber gloves, thoroughly mix 10 tbsp of trisodium phosphate and 1 cup of chlorine bleach into warm water.
Dip a nylon bristle brush into the trisodium phosphate and bleach solution. Scrub the fence wood with the nylon bristle brush and solution until the green mildew is completely removed.
Rinse the wood with fresh water to wash away the solution. Allow the wood to thoroughly air dry in the sunlight.
Apply two coats of mildew-resistant paint to the wood using a paintbrush. Let each coat of paint air dry according to the paint manufacturer's instructions.
Substitute washing soda for the trisodium phosphate. Remove severe mildew stains with a solution of 3 tbsp oxalic acid and 1 pt. water. Wear protective gear while handling the solution, since oxalic acid is poisonous. Thoroughly rinse the wood when finished cleaning with oxalic acid.