Tom Volk's Fungus of the Month for June 1999

This month's fungus is Fuligo septica, the dog vomit slime mold.

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Fuligo septica This month's fungus is really not a fungus at all, but the "dog vomit slime mold," Fuligo septica, which belongs in the phylum Myxomycota in the Kingdom Protista. Why isn't this a real fungus? Why is it crawling around your yard? I'll have the answers to your questions later. I receive so many emails from people telling me about the "disgusting thing" in their bark mulch. Some people seem almost desperate to get rid of it (short answer: you can't). Here is a representative sample of the fun emails I've received in the past year. I figured it was easier to make a web page about it than to keep answering the same questions over and over.

Email 1: I hope you can help me. I've never seen anything like this. I scattered wood chips in my yard to cut down on the amount of mud the dogs would drag into the house after it rained. I have no idea what sorts of chips they are. A collection of road side trees. Now that is has warmed up here in Kansas, this yellow foam-like stuff is "growing" in my yard. I'm afraid it might be toxic to the dogs so I keep it scooped up. It has a pungent smell. It almost looks like yellow whip cream with a little more texture.

Email 2: I'm curious about something that was growing in my flower bed (in pine bark mulch). I wish I had a picture to show but didn't think about taking one at the time. Maybe this description will do. The color of the low lying mottled mass was mostly yellow. At a first glance it appeared like someone vomited (please forgive this description). When I watered the flowers and the water stream hit it, it burst open and brown colored smoke (spores?) appeared.

Email 3: Sir -- Could you kindly help us identify the fungus/fungi growing in our flower bed? What we first thought was our dog's -- well, to put it bluntly-- vomit seems to be some kind of living, thriving fungal entity. This patch of muted golden-colored "whatever" seems to thrive in the cypress mulch-filled, wooden-bordered landscaping. Upon our initial discovery the patch was approx. 6" in diameter and 3/4" high. By sunset of Day One it had faded to a black exterior. Day Two saw it lengthen by about 6 more inches (turning golden again) and taking a liking (move) to a landscape timber (Gadzooks, it's mobile and has a brain!) . By Day 3, it seemed to produce small areas of "offspring" which continue to thrive at unpredictable intervals. My first testosterone reaction was to kill it with a shovel and/or a mixture of water and bleach, but my 9-year-old daughter insisted I let it live and surf the net for any info I could find. I did find a photo and information on a strikingly similar looking fungus; but here's the punchline. I lost the material. All I remember is that its scientific name started with the letter P and that its key characteristic was -- you guessed it -- a dog vomit appearance. As my daughter's scientific curiosities have been stimulated, so too has her insistence that we bring this creature in for a science show-n'-tell. Now her teacher is badgering me to come up with more info. So here I go. Anything you can respond with would be a great help! Thanks very much in advance for your attention.

I'm sure you can see why I'm sort of hesitant to give up the interesting emails about this organism, but I'm sure there will be others to take their place. Incidentally there's no way to get rid of it, so I recommend you just enjoy it. Some people have written telling me they keep washing away the fruiting bodies with a hose, but that just allows the swimming spores to spread more easily. There is no known danger to humans or other animals from inhaling the spores or ingesting this organism, although I don't think you will have a pleasant dining experience if you decide to try it-- I do not recommend it. Can you believe I still get dozens of emails every year about these slime molds? I get at least 5 emails per week from people asking how to get rid of slime molds, stinkhorns, cannonball fungus, and other fungi in their mulch. You can read about this on my mulch page. I will not answer any further emails about how to get rid of fungi in your yard. THERE IS NOTHING YOU CAN DO ABOUT THEM short of paving over your yard, so you might as well find some way to enjoy it. :) I hope this page helps your enjoyment.

Physarum plasmodium in naturePhysarum plasmodium in the lab In order to understand the slime molds you have to know something about their vegetative structure. They exist in nature as a plasmodium, a blob of protoplasm without cell walls and only a cell membrane to keep everything in. It is really nothing but a large amoeba and feeds much the same way, by engulfing its food (mostly bacteria) with pseudopodia. You may know this process as phagocytosis. So the slime mold ingests its food then digests it. You may recall that true fungi have a cell wall and digest their food with exoenzymes before ingesting it. The plasmodia you see here actually belong to another slime mold, Physarum polycephalum. The plasmodium of Fuligo septica is transparent, like an egg white. In fact the plasmodium is gathered and eaten in Mexico! Usually the plasmodium comes out at night and is collected by moonlight in jars. The plasmodia are brought home, where they are mixed and eaten like scrambled eggs!! If you've been reading my web pages, you know that corn smut is another unusual fungus that's also eaten in Mexico.

some slime mold fruiting bodiesSlime molds do not fit at all into the kingdom Fungi. They have been traditionally studied by mycologists because their small, delicate fruiting bodies tend to be fungal in appearance. Most slime mold fruiting bodies are really quite beautiful. In this picture A is Lycogala epidendrum, B is Comatricha typhoides, C is Badhamia utricularia, D is Dictydium cancellatum. Slime molds are often found on old well-rotted logs, because there they can find the moisture and bacteria required for survival. The fruiting bodies produce spores, which can germinate to form myxamoebae or flagellated swarm cells. These later fuse to form the plasmodium, which later forms the fruiting body. Most of the fruiting bodies are only a millimeter or two in height so it does take some searching to find them. However, it's well worth the time and effort, especially if you have a hand lens or a dissecting microscope. Their beauty is amazing. I have some more online images of slime molds here. For more information on slime molds including a world-wide directory of people who study slime molds, please visit MyxoWeb, created and maintained by Denise Binion. You can find a picture of a Fuligo septica plasmodium by Bill Roody there also.
the blobThese slime molds have also inspired a science fiction movie, "The Blob." (1958 with Steve McQueen, remade 1988). The box says "gut-wrenching thriller about an amoeba-like life-form that crashes to Earth in an American town and begins absorbing everything in sight. The Blob, a man-eating ball of plasma, falls from the sky in a meteor one lazy summer night. After devouring an unlucky hermit who lives in the woods, it moves on to battle government officials and two local teens for the lives of the townsfolk." A can't miss movie! Make sure you listen to the theme song, above and to the right. You can read more about the movie at The Blob Site (which includes info about Blobfest 2003-- including pictures!) You can also read reviews and see clips from the movie at

Occasionally people in more subtropical regions find large slime mold plasmodia in their yard and call the police, believing the blob has landed. It pays to know something about these organisms to avoid being embarrassed when the police come!

I hope you enjoyed learning something about slime molds. They're really interesting and beautiful organisms that you should be looking for on your next trip into the woods. Take them home and view them magnified by a hand lens or dissecting microscope. You'll be amazed.

If you have anything to add, or if you have corrections or comments, please write to me at

This page and other pages are © Copyright 1999 by Thomas J. Volk, University of Wisconsin-La Crosse.

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