What are those little black dots on my siding?
You may have seen artillery fungus and not even know it. The fungus resembles scaly dirt or mud spots and is found on light colored housing, cars and exterior surfaces. It is also found in manure and bark mulches.
What is Artillery Fungus?
Those annoying black spots that creep up your siding or splash along the side of your car may not be mud spatters but artillery fungus. What is artillery fungus? It is Sphaerobolus, a common fungus that sticks firmly to light or white colored surfaces and resembles spots of tar. Its adhesion properties are legendary and the spots can be difficult or even impossible to remove without damaging the surface. This common fungus is often found in bark mulch and especially hardwood mulch.
What causes artillery fungus?
The best conditions for the formation of the spores are cool, moist and shady conditions. This is why the spores are more noticeable on the north side of a house. They are more prevalent on light colored structures because the peridiole shoots the fruiting bodies towards light and light reflects best off of these lighter surfaces. It is recommended that old mulch is raked to expose the spores to light and dry out the material, or 3 inches of new mulch added over the old to suffocate the spores of artillery fungus in mulch.
How to Get Rid of Artillery Fungus?
There is no recommended artillery fungus treatment. If the spores are fresh, sometimes soap and water with a scrub brush will remove a bit of the fungus. Trying to remove them with a pressure washer could severely damage the surface they are on.