What are those black spots on my siding.


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, especially hardwood mulch, too.

A good indication is they only appear to be on the siding where the mulch beds are. One way to check is by observing if spots are along the driveway where their is no mulch. If so it may not be artillery fungus.

How It Grows?

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 spore 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. You can power wash them off of vinyl siding but such methods can be damaging to cars and wood siding. We have not found a effective or inexpensive solution to this pesky problem.

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