Dog Vomit Slime Mold, Fuligo septica

Dog vomit slime mold.

Dog vomit slime mold.

Many people get quite concerned when a whitish to bright yellow or orange patch that looks like a dog threw up suddenly appears seemingly out of nowhere on the ground. With the apt common name of dog vomit slime mold (or less accurately dog vomit fungus) the species Fuligo septica, with a worldwide distribution, is one of nature’s interesting oddities.

Slime mold Fuligo septica.

Slime mold Fuligo septica.

Even though it is often referred to as a fungus, slime molds – myxomycetes – are now thought to be a different type of primitive organism in the kingdom Protoctista (Protista) more closely related to amoebas and certain seaweeds than fungi. Slime molds do not have the threadlike filaments called hyphae (collectively called mycelium) that most fungi have in their vegetative state, but instead are made up of a multinucleate mass of protoplasm with no cell walls within a cell membrane, called a plasmodium. The plasmodium, which varies greatly in size depending on the species, moves around like a huge amoeba as the cells multiply, streaming over the surface engulfing decaying organic materials and consuming the microbes (especially bacteria) that inhabit them as it goes.

The bright yellow slime mold coming out of the ground about 9:00 p.m. (L) has transformed into a mounded light yellow aethalium by 7:00 a.m. the next morning (R).

The bright yellow slime mold coming out of the ground about 9:00 p.m. (L) has transformed into a mounded light yellow aethalium by 7:00 a.m. the next morning (R).

It isn’t until the slimy plasmodium changes into a spore-bearing “fruiting body” that most people notice it. This change occurs when its food supply is exhausted or conditions become too dry. The transformation can occur very rapidly – sometimes within hours. The “fruiting body” takes various forms depending on the species.

Closeup of the fresh aethalium.

Closeup of the fresh aethalium.

In the dog vomit slime mold, the transparent plasmodium (like an egg white) changes into an aethalium (plural, aethalia), a thickened, cushion-like, irregularly shaped structure containing numerous spores. This usually begins in the evening, so that by the next day the “vomit” has “magically” appeared. The whitish, tan, bright yellow, or orange fluffy or foamy-looking aethalia range greatly in size, from a few inches to up to two feet across. The color likely inspired another common name for this slime mold of “scrambled egg fungus”. The surface of the aethalium sometimes develops dark red liquified areas as it ages, making it look like it is bleeding.

The aethalium quickly dries up and changes color. At 7:00 a.m. the aethalium was fresh and bright yellow; by 4:30 p.m. the same day it was dry, crusty and orange in color. This large specimen was 22 across.

The aethalium quickly dries up and changes color. At 7:00 a.m. the aethalium was fresh and bright yellow; by 4:30 p.m. the same day it was dry, crusty and orange in color. This large specimen was 22 across.

The aethelium soon matures into a harder mass, losing its bright color. Underneath the crusty, powdery surface a mass of dark brown spores develops, not in distinct sporangia like more advanced slime molds have. The millions of spores are released when the surface is broken by animals, people, or rain, and are disseminated by wind to other areas. Run a stream of water onto a mature aethelium and a cloud of spores rises up like dark smoke. The mass will eventually disintegrate and disappear.

A cross section of the aethalium, showing the mass of brown spores embedded in the structure.

A cross section of the aethalium, showing the mass of brown spores embedded in the structure.

The dusty, pinkish-brown spores are round and slightly spiny (under magnification). The spores will remain dormant but viable for several years until conditions are right. The spores germinate in warm, moist conditions to form myxamoebae or flagellated swarm cells, which later fuse to form the plasmodium.

Dog vomit slime mold is most common on hardwood mulch in urban areas.

Dog vomit slime mold is most common on hardwood mulch in urban areas.

Slime molds are most often found in moist, shady areas with abundant organic matter, such as dead leaves and wood, although they may move to bright areas when ready to change to the “fruiting body”. Slime molds are saprophytic, meaning they derive nourishment from decaying organic materials, and will not attack living plants (although they might over-run a small plant in the vicinity).

Their ecological role in nature is to break down dead materials to recycle the nutrients for other species to utilize. The dog vomit slime mold occurs in forested areas, but typically causes more concern when growing near homes or buildings. This species is most commonly seen on hardwood mulch, but also occurs on rotting logs, in leaf litter, and along untreated lumber. Fresh mulch is more likely to support slime mold growth than older, more decayed mulch.

Dog vomit slime mold aethalia vary greatly in size, color, and shapes.

Dog vomit slime mold aethalia vary greatly in size, color, and shapes.

Dog vomit slime mold can occur anytime from late spring through fall. It needs moisture to thrive, so is frequently seen after soaking rains when it is hot and humid.

A slime mold moves up a 6 high wooden raised bed from the bark mulch at 7pm (L), reaching the top of the wood by 10 pm (C). The move is completed and the plasmodium tranformed to aethalium by the next morning (R).

A slime mold moves up a 6 high wooden raised bed from the bark mulch at 7pm (L), reaching the top of the wood by 10 pm (C). The move is completed and the plasmodium transformed to aethalium by the next morning (R).

Although many people are alarmed, grossed out, or frightened by it, this slime mold is harmless to plants, pets, and humans (although the dusty spores can irritate people with allergies, asthma, or other respiratory conditions). Slime molds are usually only a cosmetic problem and will disappear on their own in a few days.

Real vomit (from a cat, not a dog) that looks a lot like an old slime mold aethalium.

Real vomit (from a cat, not a dog) that looks a lot like an old slime mold aethalium.

There is generally no need to control these odd organisms, but if it is really bothering someone, an aethalium can be raked out or scraped off, or broken up and allowed to dry out to make it less noticeable. Stirring up the mulch will help break up any plasmodia as well as dry out the area to make it less hospitable for slime mold growth. Using something other than hardwood bark for mulch (such as gravel, pine bark, cedar bark, or pine straw) and reducing excessive watering will reduce the likelihood of the slime mold showing up, but won’t eliminate it. There is no way to eliminate the organism, other than getting rid of everything it feeds on, which is nearly impossible other than by paving the entire property.

– Susan Mahr, University of Wisconsin – Madison


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– Susan Mahr, University of Wisconsin – Madison

18 comments

  1. At last, I have more information for my neighbors as I have been asked by several, to identify it. I now have more to offer other than the name, which always brought an interesting reaction.

  2. I have dog vomit fungus traveling across my front porch which is wood. It seems to be growing larger every day and encroaching more and more of my porch. How can I get rid of it?

  3. My dog just ate some of this. I was glad to read your article that it won’t affect her. She is 8 months old.

  4. The dog is missing and this was found in the bark chips next to his water bowl. It had mold growing around the edges. It appeared overnight. Smelled REAL strong of mold. Thought for sure he ate something bad as he will eat about anything. Good to know he isn’t “sick as a dog”. Dog still missing….hopefully he just has a girlfriend. 🙂 Surprised I’ve never seen this before living in Oregon for 50+ years.

  5. I found this in one of my flower pots, its crept over the impatiens, and its very light yellow.
    Grows extremely fast. I need to get rid of it, so is the best way to just pick up the pot and throw it deep into the woods plants and all. Or to cover it with plastic bags so it will get hot and die. Or pour clorox on it.
    I dont want my dogs or grandkids to touch it.

    • If you read the article, you will see that it will soon disappear on its own, and it won’t hurt the kids or dogs. Really, bleach? OCD, I suspect.

    • Full strength bleach will kill the dogs and harm the grandkids, and you. You can get some pretty nasty burns.

  6. Great article, thank you. I was concerned about the birds since it is not far below my bird feeder.

  7. Best article on this slime with new info. I’ve had it previously in wood chips but this time in the mowed grass, and had to look it up again. When I went to clear it, surprised it was the consistency of whipped cream.

  8. A friend sent me a pic of this fungi growing on his worm bed. This is the first time I’ve seen whole fungi growing in the vicinity of compost worms (or earthworms). Fungi is amongst the preferred food of worms and so, it is usually eaten before it can even become visible. The comment that the dog vomit fungi eats bacteria might be the explanation though, as even though bacteria are the much preferred food of worms, a worm can host billions of bacteria in its gut. As the hosted bacteria die and decompose, they are absorbed by the the hosting worm, but concurrently, the worm’s gut is an environment very conducive to an exponential increase in bacterial population. J.N.Parle ( a New Zealand researcher) found that the bacterial population of soil was in increased by a factor of 1000 in its passage through a worm’s gut. The point I make is that if worms have a benevolent function in relation to bacteria, they would not willingly imbibe a food which would have a detrimental effect on that same bacteria.

  9. Just found some in my garden on my grass. Neighbours dog was chief suspect.
    Live in cork Ireland. Never saw it before.

  10. I thought the neighbors dog had paid our yard a visit when I spotted this mess under a pine tree! Found the article in my “extra reading” for my Master Gardening class. Now I can be assured that the dog is OK and not panic about the slime mold either. Very informative article.

  11. Great article ! Is Dog Vomit Slime Mold harmful to dogs ?

  12. What is the red liquid coming out of the dog puke fungus and is it harmfu ?l

  13. Interesting article. I’ve never seen this, but it is interesting that it can move.

    • It creeps!
      And leaps and glides and slides
      Across the floor
      Right through the door
      And all around the wall
      A splotch, a blotch
      Be careful of The Blob!
      [pop]

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