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Small Black Spots on Siding

We have these small black spots that look like specks of tar, all over our white, vinyl siding of our house. It’s on the porch, my windows, but it is worse on the siding. It goes all the way up to my second-story windows, and is even under my soffit and on my gutters.

You have the infamous “artillery fungus. The artillery fungus is a white-rotting, wood-decay fungus that likes to live on moist landscape mulch.

It is in the genus Sphaerobolus (Greek for “sphere thrower”) and is very common across the USA, especially in the East. It also called the “shotgun fungus”.

The term artillery refers to the fact that the artillery fungus actively (uses energy) shoots its spore masses, sort of like a cannon or howitzer (an artillery piece). We will call these “spores,” although they are technically spore masses, or gleba. The spores are usually shot only a short distance but the wind can carry them for longer distances.

The spore masses of the artillery fungus stick like super-glue. We have not found an efficient way to get them off without leaving a stain on the siding. There is nothing you can spray on mulch beds to prevent the growth of artillery fungus either. Beware of any cleansers that have claims that sound “too good to be true”, with regards to removing the artillery fungus. It is likely that they are, in fact, too good to be true. Don’t be fooled by contractors who claim these spots are fly or spider droppings, they are not.