Q: I have tiny black specks on my siding at the front of my house that are almost impossible to remove. There are too many to scrape off with a fingernail and then scrub the remaining residue. They are like little specks of tar. When I called the siding company, they felt it was due to spores from mulch. This seems strange, since I have mulch all around my house but a problem only on the south side where it is sunniest. Have you ever heard of this problem? Is there a product I can use to clean my siding that will dissolve the specks, and how can I keep it from happening again?
A: The siding company is right. The culprit is artillery fungus, also called shotgun fungus. It lives in wood mulch and shoots tarry spore packets at sources of light, which can include the light reflected off light-coloured siding, cars and other surfaces.
Raking the mulch to break up matted areas may stop additional spots. If not, you'll need to remove the mulch.
Unfortunately, removing the existing spots is difficult, especially after they've been in place for a while.
Donald D. Davis, a plant pathologist at Penn State University, has a good overview of the fungus. It includes suggestions he's received from the public for removing the spots, but he cautions that he hasn't tested them.
Interestingly, he said many people have had success with a process a 10th-grader developed for a research project: Clean off the spots with Cinnamon Ice Scope mouthwash and paper towels, and then remove the remaining stain with Crest MultiCare Toothpaste and additional paper towels. One person successfully substituted a Mr. Clean Magic Eraser for the toothpaste-and-paper-towel step.
Cinnamon Ice Scope is no longer manufactured, but you can order it from Amazon.com.
