Slime Mold on Lawns

What It Is, How to Get Rid of It

slime mold
Ed Reschke / Getty Images

A reader of my Landscaping website asked a question about slime mold. He had spotted some on his lawn ("a foot in diameter for each patch," states the reader) and tried to get rid of it. First, he tried applying tea tree oil, then he tried hosing down the area full-blast. Neither treatment had any affect on the substance.

So he turned to my landscaping site for answers on getting rid of slime mold. As it turns out, perhaps the most important answer he received is that slime mold is not a major problem to worry about.

Slime Mold: Starving a Saprophytic Fungus

Peter Rennie, RPF Consulting Forester and Arborist and contributor to my site, handled this question on slime mold. Peter began by stating that slime mold is not, technically, a lawn disease, but rather a saprophytic fungus (i.e., it is an organism that lives on dead organic matter).

So the most logical way to get rid of slime mold is to cut off its food supply of dead organic matter. What dead organic matter resides on your lawn? Well, you certainly should be raking up leaves and twigs that have fallen on your lawn. But one of the biggest culprits is more difficult to see: lawn thatch. De-thatching your lawn can sometimes seem like just so much busy work: until something like slime mold comes along. Then you begin to realize the importance of de-thatching the lawn.

Other Ways to Get Rid of Slime Mold

Peter also recommends the following for getting rid of slime mold:

  • "allow more sun onto the lawn" (see below)
  • "reduce watering for a while to allow it to dry out" (see below)

As for using fungicides to get rid of slime mold, Peter writes that Mancozeb will control the problem, but that it is "not considered worth the cost."

"So, first," continues Peter, "I would suggest getting a steel grass rake and rake the lawn hard (good exercise, you won't need to go to the gym). Or get a thatching blade for your lawnmower (looks like a regular blade but has two wires aimed to the ground to break up the thatch).

"If you have moisture problems (low spot), try topdressing with sand and then overseeding. If you have big shading trees, you may want to thin them a bit to allow more light and air movement."

A Reassuring Conclusion

Peter ends with some information that may actually be more important than the tips above on getting rid of slime mold. Namely, he assures us that while slime mold "looks nasty," it isn't "dangerous."