Dog Sick Slime Mould (Mucilago crustacea)

By | 11/06/2018
Slime Mould mucilago crustacea

This wonderful example of a slime mould recently appeared on my test lawn. It is a great example of the colourfully named Dog Sick Slime Mould (Mucilago crustacea).

This example was about 30cm in length and a bright cream colour. It almost shone compared to the green grass surrounding it. It appeared very quickly (overnight) and then had turned black and faded less than a day later.

I rarely see these on lawns so it was a treat to be able to observe one appear on my own test lawn.

What is a slime mould?

They are not a plant or animal. They are a huge collection of single-celled organisms called Protozoa, specifically in the taxonomical class called Myxogastrea. When the conditions are correct (similar to lawn fungi) they bloom and spore in huge numbers. This is the structure which becomes a slime mould. Once they release their spores for the next generation, they collapse and die.

They can vary greatly in size and colour, but are most often grey, yellow or white.

This example I captured below is one of the most common in the UK. It is called Mucilago crustacea or dog sick slime mould. This is due to it’s rather unpleasant look on the grass. If you look carefully though you can see that it is intricate and delicately grows up and around the grass leaves.

Slime Mould mucilago crustacea close up
A closer look at the slime mould on the lawn.
Close up of a mucilago crustacea
Close up of a Mucilago crustacea. Notice how it is enveloping the grass leaves, but they remain unharmed.

Do slime moulds harm my lawn?

Slime moulds do not harm grass. They grow up in and around the grass leaves and obtain their food by smothering bacteria, spores and tiny organic matter as they grow.

They may leave an unsightly black “splodge” on the grass. This can be easily removed with a rake or the mower.

Control of slime mould

As it does not harm the grass there is no need to control it with treatments. If it looks unsightly and you would like to get rid of it, then you can squirt it with a jet of water to wash it off.

It can also be raked or brushed out and will disappear soon.

If you have a strange growth on your lawn I would love to see a picture of it. Please get in touch on my ask a question page.

Kris Lord

Further Reading

Mucilago crustacea - 1 Day Later
The same organism the next day. It has turned black and reduced in size.

Reader Submitted Photos of Slime Moulds

Here are photos which have been sent in by readers via my ask a question page.

User Submitted Slime Mould
This fantastic specimen was sent in by David Crouch.
Reader submitted slime.
This one was sent in by Richard.
A white slime mould on grass
Reader, Zoe sent in this interesting example in the winter of 2019
A white slime mould on a lawn
Reader, Jerry sent in this large specimen in the summer 2020.
A really nice slime mould sent in by James in June 2021.

12 thoughts on “Dog Sick Slime Mould (Mucilago crustacea)

  1. Dee Brown

    There seems to be a lot of this about at the moment. I have started to have bright yellow patches appear on my lawn, just from this week. None has ever appeared before in all my years in my house. Every day there is a new patch appear, I just brush it off. after reading about it. I hope this is correct

  2. Jude

    We keep getting patches of dog sick slime mould on our front lawn – this started a week or so ago and every day there is another patch. How can we stop this? Or will it eventually disappear on it’s own accord?

    1. Kris Lord Post author

      I would not advise eating huge colonies of Protozoa bacteria. Dog or otherwise.

    2. Maureen edwards

      Is it actually dangerous to dogs. I walk my dogs daily in the field where it is but they are not attracted to it at all. When i first saw it i thought it may be either fox or badger sick

    1. Kris Lord Post author

      Hi Antonio,
      That does look like a slime mould, but I cannot say for sure which species it belongs to. I am not an expert on Slime Moulds I’m afraid, I just find them interesting.
      Thanks for your interest.
      Kris Lord
      The Lawn Man

  3. Stephan

    We have just discovered several patches of slime mould in our orchard field. We’re near yo Honiton. Took some photos earlier today which we could send you if wanted?


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