[Grubbypaws]

Hi, yesterday I noticed strange white patches had appeared on my lawn. Today they are turning black. Has any one any idea what they are? I am presuming it is some kind of mold or fungus but I have never seen this before.

[Yorkie]

Slime moulds?
https://www.rhs.org.uk/biodiversity/slime-moulds-on-lawns

[Subversive_plot]

I agree, slime mold is the likely answer.

I see the same thing here, they disappear as quickly as they appear.  Usually no trace remains after they vanish.