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What is the Fungus on Our Lawn?

By: Dr Gareth Evans - Updated: 22 Aug 2017 | comments*Discuss
 
Slime Moulds Fungi Damp Rain Aeration

Q.

We have a fungus spreading on our lawn and would appreciate comments as to how to deal with it. It starts as bright yellow small 'bubbles' on the stems and grows quickly to a whitish covering.

The pictures attached show progress. Any help would be appreciated.

(Mr Leslie Oppitz, 8 September 2008)

A.

Although what you’ve photographed does look for all the world like a nasty fungus infection, what you have on your lawn actually isn’t a fungus – it’s a slime mould – and the good news is that although it’s a bit unsightly, it’s not harmful either.

Slime Moulds

Slime moulds are fascinating and rather weird things that spend part of their time behaving like fungi and the rest behaving like very simple animals. For years no one really knew how they fitted into the tree of life – with both mycologists (fungus experts) and protozoologists (single-celled animal specialists) each claiming them as one of their own. The puzzle of where they fit into life on earth was ultimately solved by DNA analysis and to cut a long story short, the slime moulds (and there are many different kinds) got a separate special biological group all to themselves – the “Protoctista.”

OK – very interesting, but what about our lawn?

First of all, don’t worry about your garden; your grass isn’t being damaged, slime moulds don’t usually affect other types of plants – although they can occasionally – and they aren’t harmful to the soil. I’m not sure when you took these pictures, but slime moulds tend to be more often seen like this in the spring and then again in early autumn and most usually when there’s been a period of heavy rain. Although where I live has been quite dry this summer, I’m guessing you’re in one of the areas that has been a good bit wetter – which probably triggered this outbreak in your garden.

A Simple Cure

Since slime moulds aren’t a pest as such – they just make the garden look a little ugly for a while – and they do have a minor role to play in helping keep the soil in good condition, generally the best solution is simply to wash them away with a hosepipe.

Although some fungicides are effective against slime moulds, there’s really no need to reach for them. Once you’ve solved the immediate aesthetic problem and washed all the “scrambled egg” off your grass, you might want to think about a spot of prevention.

A Spot of Prevention

You’ll probably already have noticed that once the yellow bubbles have turned whitish as you describe, they will eventually go more greyish – this happens when the slime mould is releasing spores, which will then end up down in the soil. Which means, they’ll be back if you don’t address the conditions that brought them out in the first place.

Obviously you can’t do much to stop it raining, but from those great photographs you sent in it looks as if the patch of affected grass is in a dampish spot, judging by other plant leaves in the picture – so improving the drainage here should help stop it happening again.

Try to rake up any of the dead plant material from the patch and then spike the ground with a rotary lawn aerator if you have one – or a trusty garden fork if you don’t – and then leave everything alone over the winter. Next spring, spread sharp sand over the area and let the worms do their stuff. You’ll soon have better drainage, well aerated soil and the slime moulds should stay where they belong – out of sight!

Fascinating though these strange living organisms are, they’re not exactly pretty!

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@dobbie57 - it's hard to say. newly laid lawns are under a lot of stress so they are prone to disease, especially in late autumn and especially after a lot of rain. It could be Fusarium where at first small yellowy brown patches form on the grass, plus a white fungus that clings and rubs off. Feed your lawn and this should clear next spring as the lawn becomes healthier and more established. It could also be be a shortage of nitrogen and Red Thread which is a leaf disease but generally hits more established lawns (it depends where you got your turf from). Hopefully it'll sort itself out. If not ask the supplier directly. GRW
R - 24-Aug-17 @ 2:49 PM
Hi I would appreciate some advice re a newly laid turf lawn (now almost 4 weeks old). The problem is that we have noticed quite a few yellowing blades of grass throughout the entire lawn ie. not patches. On close inspection there seems to be bands of green yellow and brown across the blades. Bit disappointed really as it looked so good for the first two weeks. , and still does but for the above on close inspection. We are in a new build house and the soil is quite poor with lots of stones. Did the best we could re cultivation, removal of the biggest stones and raked a layer of potting compost over the surface prior to laying the turf. watered using sprinkler every night. First cut after 2 1/2 weeks with a flymo hover mower set to cut at maximum height as growth was strong and turf seemed well rooted and would not pull free of the soil below. Second cut as above at 3 1/2 weeks as a lot more growth had been made. would really like comments on what this could be and what can be done as although the grass looks well from afar the yellowing seems to be getting worse. Kind Regards Dob.
dobbie57 - 22-Aug-17 @ 1:21 PM
Tomisal - Your Question:
I have a small front lawn and over the weekend it has been infested with what looks like small greyish mushroom shaped fungus. I had a few last year but they have really spread. Also on my larger back lawn I have lots of brown mushroom/toadstools. Again a few last year lots this year. Any help would be welcome

Our Response:
While you may think your mushrooms may be a blight, most fungi in lawns are greatly beneficial as they decompose organic matter, and thus help release nutrients to help plant growth. Mushrooms are the fruiting bodies of fungi which have stemmed from the underground mycelia from which they grow, so picking the mushrooms as soon as they sprout will prevent their spores from spreading. Over-irrigation or poor drainage can encourage the growth of mushroom and if you have a dry lawn they will tend to disappear. In a D-I-Y way, aerating the soil to improve drainage may help. Getting rid of the likes of; pet waste, rotting leaves/mulch, old tree stumps, which provide a good food source for the mushrooms will help too. But in other terms they are generally good for your plants and lawn.
LawnExperts - 1-Nov-16 @ 12:11 PM
I have a small front lawn and over the weekend it has been infested with what looks like small greyish mushroom shaped fungus. I had a few last year but they have really spread. Also on my larger back lawn I have lots of brown mushroom/toadstools. Again a few last year lots this year. Any help would be welcome
Tomisal - 31-Oct-16 @ 4:34 PM
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