Dog vomit fungus, it's harmless and just decomposing organic matter in the soil. Though err, why would you post this in the hellebore forum ?

This post was edited by dbarron on Mon, Jan 5, 15 at 16:24

That is a very common organism called a slime mold. Slime molds are harmless to everything, some cultures consider them edible. The name is misleading as they are not a mold nor a fungus, but a protist and they exist all over the world. Your particular species is commonly called the dog vomit slime mold, for obvious reasons.

It will soon die off, leaving your lawn in fine shape. I strongly advise that you do not use any chemical means to get rid of something harmless and interesting.

Please put your fungicides away. Pesticidal chemicals should only be used when you know the identity of the pest.

Here is a link that might be useful: info about your slime mold