Artillery fungus is causing a lot of problems for us this year. It's an organism that breaks down wood and is commonly found across the United States, including in landscape mulch. The mature fungi are a mere 1/10 inch and are very difficult to see. The spore clusters, however, are not. This fungus spreads via spores that are shot out for several feet, appropriately earning them their name.
Artillery fungus is so troublesome because the spore clusters are extremely difficult to remove from the surfaces where they land, including cars, house siding and garage doors. At our house, the spores have landed on the white siding across the back of our house. As we’ve discovered, artillery fungus naturally shoots its spores toward sunlight and reflective surfaces, so it’s often more problematic on light colored homes and cars.
As with all fungi, artillery fungus prefers moist, shady conditions, so our problem is more pronounced on the north side of our home where it’s shady.
To help manage the problem next year, we may use mulches made from bark rather than shredded wood, as this organism tends to prefer wood products. I understand that pine bark nuggets are a good option, as are cocoa hulls. I'll probably end up removing as much of the infested mulch as possible, bagging it or throwing it far into the woods before adding any new mulch. I guess another option would be for us to use river rock, pea gravel or mushroom soil as alternative mulch. We could also plant a ground cover. None of these support artillery fungus.
Even though they’re a mess to clean up, the spore cases will not harm our house. Other than the marks they leave behind, they aren’t destructive. It is nearly impossible to remove the spores from siding, though, if we really wanted too, we could power-wash the siding and scrape them off with steel wool. That seems like an awful lot of time and effort and probably isn’t worth it. I’ve also read that Simple Green cleaner will remove the spots from siding, but I haven’t tried it myself.
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