Artillery fungus -- the black mould spores that grow on cool, moist wood -- are especially problematic on house exteriors. The spores are unattractive, particularly on light-coloured paint, and can aggravate allergies. The fungus thrives in foundation mulch found around the house and spreads to the exterior walls. Removing mould spores can be tedious, but if you take preventive measures afterward, it should solve the problem.
Bag up the mulch under the affected wood and throw it away. This will get rid of fungus thriving in the mulch.
Power wash the affected wood with a pressure washer. This should remove the bulk of the mould from newer wood, though it isn't a very successful method in older wood. If mould remains, you will need to scrape the spores off.
Place a tarp under the affected area to catch falling spores as you scrape. This will prevent future infestation.
Scrape mould spores off with a scraper, sandpaper, steel wool or a combination of the three.
Coat the affected area with mould-proof paint to seal any remaining spores and cover stains.
Wash your tarp thoroughly to eliminate the spores.