Hello,

Thank you for contacting Ask Extension. I have a few questions to ask you. Are you referring to the blackened or the light brown areas in the bed? If not, what areas specifically? Do you use mulch or leaves in your beds? When did you start seeing this? How much sun does it get daily? and Does the area drain well or does water stand for a while here?

Once I get these answers, I will be better equipped to answer your original question.

Thank you for contacting Ask Extension. This is a slime mold with the scientific name Fuligo septica. It is harmless, although people sensitive to molds should be cautious if they are going to work around it, using a mask and gloves. There is no way to totally prevent it, it occurs in nature as organic matter break down; you can discourage it by letting wet areas dry so it doesn’t stay too wet for long periods. It can be raked up and thrown away whether it is wet or dried out. Some people find using a strong stream of water on it to break it up, especially if sun will then dry it out quickly, can help. Try watering the susceptible areas early in the day so daylight helps the surface dry before nightfall. Slime mold fungus, also called dog vomit, is harmless to people and pets.

Slime molds are fungi which feed on decaying organic matter or live on the surfaces of grass foliage. These molds inhabit the upper layer of soil, the thatch layer and the foliage. During
warm weather, following a rain or heavy watering, slime molds will form a creamy white or gray-colored slimy growth on the foliage. The molds develop in streaks or small patches 2-6
inches in diameter, and are often associated with heavy morning dew. The grass blades are used only for support by the mold and are not directly damaged. However, this growth will eventually change to an ash-gray crusty mat, which dries on the grass blades, and can indirectly damage the grass due to shading and smothering. It should be noted that the development of slime molds in lawns is relatively rare, and usually will not occur more than once a season.

No chemical treatments are recommended for slime molds, and raking, brushing, or spraying the growth with a stream of water can remove it from the grass blades.

Here are some publications for your reference:

https://botanicgardens.uw.edu/about/blog/2017/06/07/june-plant-profile-discovering-slime-molds/

https://archive.lib.msu.edu/DMC/Ag. Ext. 2007-Chelsie/PDF/e1516-1986-print2.pdf

Both areas pictured are on sloping ground, so no standing water. We have it in our lawn and a flower bed. It started about two years ago and is spreading. No mulch, both areas receive some sun each day. Our soil is heavy clay. It reminds me of a slime mold. The first photo is from the flower bed. Two and three are in the yard. We first noticed it in the flower bed, The areas are not contiguous. 

Additional thought. We live on a lake, Lake Lancer in Gladwin County which we use to water our yard and flower garden. Could that be involved?

Thanks