Extension ServiceBlack slime in my barkdust, is this a concern?
We had new tanbark laid down in our backyard and have been finding black tar looking patches after it rains. We clean them up...then it rains and new patches of it show up again. Have you seen this before or have any idea what it is??? Three more patches of the stuff this morning after last nights rain. I've sent pictures and also have saved the globs should you need them to help with identification.
This is a slime mold, which is a non-pathogenic fungus that feeds on organic material, not uncommonly large, freshly applied batches of organic matter like bark dust. They tend to appear and disappear equally quickly. They are really a curiosity more than anything to worry about. There seems to be a lot of this as I've had three Ask an Expert inquiries on this same topic this week. I include a link to a short discussion of slime molds from the PNW Disease Management Handbook.
