Best treatment for slime mold? Do nothing

By Lillian Quaranta

OSU Ext. master gardener volunteer

Yikes! Bright orange, slimy and 15 inches across! It looked like dog vomit on the mulch in my perennial flower bed. All I could think was, “Are you kidding me?” Just when I think the weather, the flowers and the deer have decided to cooperate with my garden plans, I see this stuff. My knee-jerk reaction was to hose it out of the bed, but as soon as the water hit the orange mass, puffs of “smoke” covered the bed. The mass did seem smaller, though. Maybe with another hard squirt it could be gone. Right? Wrong!

Novice gardeners shouldn’t wing it. Proof of that came the very next day in the Pest and Plant Clinic. A local gardener brought in an 8-by-10-inch sample of a mysterious anomaly in his garden that was identical to mine. With research, I discovered its name: “slime mold.” Further research unearthed another interesting fact – water helps spread the spores (“puff of smoke”) throughout the garden. Oops! Instead of using water, the University of Illinois suggests eliminating it by shoveling the spore mass into plastic bags. Also, hard raking/brushing helps the area dry out, reducing the mold’s source of nutrients. But the best management for slime mold is nothing, except to let nature take its course with a good supply of hot, dry weather. (But be careful what you wish for!)

Scientists have been studying slime mold for years and labeled it “mold.” Molds are a fungi, and slime mold is neither a mold nor a fungus. One of the components of a fungus is its inability to move at any stage of its life cycle, according to the University of Utah. Slime mold moves. This amoeba-like organism has been reclassified from the Kingdom Fungi to the Kingdom Protista. Frederick Spiegel, a biology professor at the University of Arkansas, said when he first saw them, “I thought they were the most beautiful, sublime things I had ever seen and had to work with them.” That was more than 40 years ago. He has now discovered over 900 species globally with his colleagues.

The most interesting discovery I found was the slime-mold experiments of a computer scientist, Selim Akl of Queens University (a must-see, slow-motion video). He concluded that slime mold was “fantastically efficient at finding the quickest route to food.” His experiment (replicated globally) of placing rolled oats over a map of major Canadian cities and inserting a slime-mold culture at Toronto showed that slime mold quickly developed tentacles that connected the major cities and mimicked the Canadian highway system “in less time than humans could.” A determined, bright-colored, single-cell organism that works more efficiently than humans!

Visit to learn more about slime molds.

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