It is Slime mold time again in central Iowa and I have had several questions on it in the past week.
Wet weather increases the occurance of slime mold in turf. This problem is caused by primitive fungi that exist primarily as saprophytes (organisms that live on dead organic material) and use living grass plants for support. Fungi in the genera Muctlaga and Physarium are usually the causal agents. They can take on a wide variety forms. Sometimes people describe it as something that looks like the dog threw up on the lawn. Other times it looks like gray slime on the leaves. Then, it can take on some truly strange appearances that you would not associate with a fungi.
The fungi can be washed off with a hose. It will usually go away after the wet dreary weather changes. We generally do not recommend fungicides for this problem.
I have attached two new pictures from this week. The first is from Larry Ginger of American Lawn Care in Des Moines. The second is from Bruno Novotny who works at a course in Forest City.
The others, come from an older post on slime mold (June 4, 2013)