Mold spores grow easily on damp wood, whether the wood is outdoors or inside the home. Mold can manifest in a variety of colors. On wood, it sometimes looks like white dust or fuzz. Molding wood usually develops a distinct musty odor that won't go away until you've cleaned and killed the mold. Since mold is unattractive and often triggers allergic reactions, it's important to remove the mold.
Put on rubber gloves, safety goggles and an N95 dust mask. Fill a 5 gallon bucket full of warm water. Add 1/4 cup of laundry detergent. Mix the detergent into the water.
Wet a cloth in the detergent and water. Wipe the cloth over the moldy wood to wet it with the cleaning mixture.
Scrub the wood gently with a soft-bristled brush to remove mold from the wood's pores and crevices. Wipe it again afterward with a cloth dipped in the cleaning solution.
Allow the wood to dry until it is dry to the touch. This may take 24 hours or more, depending on humidity levels.
Rinse out the 5 gallon bucket. Refill it with 1 gallon of water. Create a mold-killing solution by adding 1/2 cup of chlorine bleach to the water, if you aren't concerned whether the wood gets bleached. If you don't want to risk lightening the wood, instead use a commercial fungicidal cleaner and follow directions on the label regarding dilution.
Sponge the mold-killing mixture over the wood. Allow it to air dry completely, without rinsing.