So you’re minding your own business, and one day you see little black spots on your house, and on your car. You try washing them off. You try to scrape them off, but they won’t budge.

artillery fungus on siding

You, my friend, are a victim of Sphaerobolus stellatus , otherwise known as “shotgun” or “artillery” fungus.

Artillery fungus likes to live in organic matter, such as wood chip mulch, and it has a cunning way of spreading itself around. When enough water accumulates in the specialized cup-shaped cells, they invert, causing other cells to burst and propel the spore packets, or peridioles, up to 18 feet away, (as high as the second floor of a building!) where they immediately stick to new surfaces. Wet, cooler weather, like our rainy early summer, is ideal for spreading the fungus.

Using an incredibly strong natural adhesive, the periodioles stick themselves to brightly lit and/or pale-colored surfaces, such as vinyl siding. They look like small, dark spots. While they don’t cause any serious damage, artillery fungi are nearly impossible to remove without damaging the surface or leaving a stain. If you catch them very early, you may be able to get them off using a pressure washer and very hot water, but if they’ve been there for a while even that won’t work. To add insult to injury, if you decide to throw in the towel and replace your siding, the insurance company may not cover what it considers to be “mold damage.”

artillery fungus growing in wood mulch

If the fungus is a serious problem in your area, you can treat the area with a fungicide, and coat your siding with a material that inhibits the growth of mold and fungus. Even if spores do appear, they will be attached to the coating, not the siding, and, therefore, easier to remove.

But you can save yourself a lot of money by simply avoiding wood mulches – especially those made from ground up pallets – which can harbor the fungi. Switch to composted mulches, stones or gravel instead.

For more information on artillery fungus, click here or here.