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Slime Mold – Only A Cosmetic Problem

Although black or white streaks are shocking when they appear on an otherwise healthy lawn, the incidence of slime mold is rarely harmful.

Closeup: Slime Mold in Centipedegrass. Image courtesy Matthew Orwat

Closeup: Slime Mold in Centipedegrass. Image courtesy Matthew Orwat

Slime mold is actually caused by the reproductive structures of an array of different organisms, classified as plasmodia or Protista, which are regularly present in the soil. They are often mistaken for fungi. The different types are referred to as myxomycetes or dictyosteliomycetes. They usually appear on warm humid days in late spring or early summer after extended periods of rain. This extended period of heat and humidity, as is currently being experienced in the Florida Panhandle, initiates the perfect climate for slime mold development.

Slime Mold in Centipedegrass. Image Courtesy Matthew Orwat

Slime Mold in Centipedegrass. Image Courtesy Matthew Orwat

As depicted in the picture above, slime mold makes the lawn look like it was just spray-painted with black or grey paint. The round fruiting bodies, called sporangia, carry the spores which will give rise to the next generation of the “mold”. After a few days the sporangia will shrivel up, release the spores and leave no noticeable trace on the lawn.

 

Slime Mold Sporangia. Image Courtesy Matthew Orwat

Slime Mold Sporangia. Image Courtesy Matthew Orwat

Currently, no fungicide exists to control slime mold because chemical control is not necessary. An excellent method to speed up the dissipation of slime mold is to mow or rake the lawn lightly. This will disturb the spores and hasten their departure. Another effective removal method is to spray the lawn with a forceful stream of water.  This process washes off the slime mold sporangia and restores the lawn to its former dark green beauty.

Excessive thatch accumulation also increases the probability of slime mold occurrence.

 

 

 

For more information consult your local county extension agent or read the Alabama Cooperative Extension publication Slime Mold on Home Lawns.

4 Comments on “Slime Mold – Only A Cosmetic Problem

  1. Hi Matthew:
    Thanks for this useful article. This year we had some erosion mitigation done to our front yard that included all new turf. This was an expensive, yet successful fix to a long standing problem. The new centipede is doing great, however I freaked out yesterday when I saw slime mold in a few places. With all the rain lately I figured it was a fungus. This morning there was another patch. I began thinking about anti-fungal treatments. Thanks to your article I now know that it’s mostly harmless and temporary. Thank you.

    Lee Berger
    Tallahassee

  2. Hi! Is it safe for children and pets to play around?

    • I am not aware of any issues with this fungus for children and pets. Spraying with a forceful hose end and raking should remove it.