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Beware wood mulch within 30 feet of your car or home

Thursday - 10/13/2011, 4:45pm  ET

A closeup image of artillery fungus spores on wood mulch. (Photo/Tom Holman)

Wood mulch wrecks new car

Eric in Silver Spring laments: "For several weeks I was baffled by the spots on my new light silver Subaru. Trips to the car wash didn't help, and scraping them off with a fingernail leaves a sticky black residue that seems impossible to remove. I recently learned that the heavy layer of oak mulch I applied to my landscape can be a perfect breeding ground for artillery fungus spores. I looked at the mulch carefully and found hundreds of the 'spore launchers' (I've attached photos of these spent fungal cannons.) I realize I need to remove the mulch, but how do I remove the spots on my car?"

Sorry, Eric -- but to the best of my knowledge no one has yet been able to find a way that doesn't destroy the car's paint job. You're probably best off just having the car stripped and repainted. (Your car insurance may help cover some of the cost. Your home owner's insurance probably won't -- most companies, stunned by the number of claims they were receiving, specifically wrote outdoor fungal damage out of homeowner's policies some years back.)

Listeners beware -- this IS what happens if you use any kind of wood mulch within 30 feet of your home or car.

Here's a great page from the Penn State Extension office that answers Frequently Asked Questions about the spores.

Wood mulch wrecked her home and car

Kristina in Falls Church writes: "Sadly, we did not heed your warnings about artillery fungus, and spread wood mulch in preparation for a big birthday party -- CONFIDENT that nothing horrible would come out of such high quality wood mulch. Now my WHITE car, WHITE front door, WHITE porch and WHITE siding are covered with tiny dark brown specks of hardened artillery fungus gunk. We had the mulch removed; any suggestions on how to clean the spores off these surfaces?"

Sorry Kristina, but I have to repeat that when it comes to fragile automotive finishes, decades of research have failed to identify a cleaner that works. The only answer seems to be stripping the car down to bare metal and having it repainted (or find a time machine and heed my warnings: It'd probably be cheaper!) As above, ask your car insurance company if they can help with the cost.

The news may be a little better for your door, siding and porch. This page from the Penn State Extension Office lists dozens of spore removal methods that homeowners have reported trying, with some claiming success. Read the page all the way through -- that's every entry -- before you try anything.

And be warned: I have been studying this problem for over 20 years (and have been warning our listeners about the dangers associated with wood mulches for the decade I've been on WTOP), and none of the many hundreds of people who have emailed me about the spores have ever written back to report removal success -- just destruction of the surface they were working on. I do not personally or professionally recommend any of the techniques on the Penn State page, and feel that sanding and repainting is the safest, surest way to go.

But if you DO try something that works, please report it to me; this topic is way short on good news.

How do you get leaves off a tender new lawn?

Mark in Reston writes: "I aerated my lawn in late September, put down compost and reseeded the bare areas. My new grass is now about an inch or two high, and is starting to be covered by leaves, which will only continue to get worse, as I have lots of trees in my yard. Should I remove the leaves? If so, how do you recommend I go about it so that I don't uproot the new grass?"

Yes, Mark, those leaves MUST be removed or they'll smother the new lawn.

This is one big reason I urge people to sow seed in late August so that the new grass is a little older and tougher when the leaves come down. If your new grass were three inches high, for instance, you could use a mulching mower at its highest setting to pulverize the leaves into a nice little fall feeding for your new turf.

But no worries. Just suck them off with a leaf blower set on reverse; and use the shredded leaves for mulching and compost making.

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