Garden Q&A: Artillery fungus hard to battle
Question: We've got a problem with artillery fungus shooting spores on our white siding and cars. What can we do about it that won't cost us a fortune?
Answer: Artillery fungus is an organism that breaks down wood and is commonly found across the United States, including in landscape mulch. The mature fungi are very small, measuring a mere one-tenth of an inch. Because they are so small, they are difficult to see. The spore clusters, however, are not.
The organism spreads via spores that are shot out of the fungus for several feet, appropriately earning the name artillery fungus. They are troublesome because, as you have discovered, the spore clusters are extremely difficult to remove from the surfaces where they land. They are nearly impossible to get off cars, house siding, garage doors and anywhere else they land. 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 fungus, artillery fungus prefer moist, shady conditions, so it's likely that your problem is more pronounced in shady areas and on the north side of your home. Years with wet springs often bring more of a problem with this fungus.
To help manage your problem, use mulches made from bark rather than shredded wood, as this organism tends to prefer wood products. Large pine bark nuggets are a good option, as are cocoa hulls.
Remove as much of the infested mulch as possible, bag it, and throw it away before adding any new mulch. Many gardeners report less of a problem when the beds are mulched with a fresh layer of product every season.
You also might consider using river rock, pea gravel or mushroom soil as an alternative mulch. Or plant a ground cover. None of these supports artillery fungus.
The spore cases will not harm your house or car, and other than the marks they leave behind, they aren't destructive. It is nearly impossible to remove the spores from siding, though sometimes power washing and/or scraping them with steel wool will work to some extent. This is a lot of time and effort and isn't worth it for most people. There is little you can do if artillery fungus spores land on your car other than gently picking them off with your fingernail.
Horticulturist Jessica Walliser co-hosts “The Organic Gardeners” at 7 a.m. Sundays on KDKA Radio. She is the author of several gardening books, including “Attracting Beneficial Bugs to Your Garden: A Natural Approach to Pest Control” and “Good Bug, Bad Bug.” Her website is www.jessicawalliser.com.
Send your gardening or landscaping questions to firstname.lastname@example.org or The Good Earth, 503 Martindale St., 3rd Floor, D.L. Clark Building, Pittsburgh, PA 15212.