The small black fungus spores on your siding are most likely from artillery fungus.
Artillery fungus is a type of fungus that grows in wood chip mulch and decaying wood. It is most common in areas with wet weather. The fungus produces black, spore-filled spheres that can be shot out of the mulch on to your home’s siding, windows, and doors causing permanent damage. In most cases pressure washing or soft washing will have little effect on removing the small black tar like spores, and a more aggressive method like scraping each spore off one by one will be required. However, this can cause damage to the material underneath so painting might be required. If you find artillery fungus in your mulch, remove it immediately. Do not compost it, as the spores can survive the composting process and spread to other areas.
There are a few things you can do to prevent artillery fungus:
- Choose a different type of mulch. Artillery fungus is most common in wood chip mulch, but it can also grow in other types of organic mulch, such as pine bark mulch. If you live in an area where artillery fungus is common like Tallahassee, choose a mulch that is less likely to be infected, such as rubber mulch or pine straw.
- Keep your mulch dry. Artillery fungus does not thrive in dry conditions. If you live in an area with wet weather, try to keep your mulch as dry as possible. You can do this by stirring it up regularly.
Inspect your siding regularly for signs of artillery fungus. If you see any, remove the affected mulch as soon as possible. If you have a large area of artillery fungus, you may want to consider hiring a professional to remove it.