Fungus Among Us
Fungi are the most commonly encountered organisms that call our grass and mulch beds home. They are everywhere in your landscape (and your home), mostly living as saprophobes (eating dead material and organic matter). By doing this, the fungi serve a critical role in our ecosystem and if it weren't for them we would be walking on logs and tree limbs. Other fungi can be plant pathogens, causing diseases in our gardens, trees, ornamentals, and (my discipline) turfgrass. Some fungi can also cause human disease, but they are rare and normally afflict immuno-compromised individuals or those with severe allergies. For this reason, if you smell or see fungal molds in your garden mulches there is not much need for alarm. They are just enjoying the buffet you put out for them!
One of the more striking inhabitants of our grass and mulch beds may be a member of what are termed "slime molds". The slime molds are not related in the least bit to fungi.,
A select few slime molds can be plant pathogens, the most famous (to us plant pathologists) being Plasmodiophora brassicae, which causes a disease called "clubroot of cabbage." For the most part though, they simply are predators of other microbes that they absorb through their cell membrane. Interestingly, they also reproduce by spores and some slime molds can produce fantastic spore-bearing structures that can mimic fungal structures. Slime molds that frequently sporulate on turf do no harm to the grass, and no control measure is necessary
The most common slime mold that is brought to our attention by alarmed homeowners is Fuligo septica, the "dog vomit" slime mold (Figures B & C). Some call this a fungus, which is incorrect. It is a common inhabitant of bark mulch where bacteria and moisture are in ample supply, and normally first appears after frequent rains in spring or early summer. In its early growing stage, F. septica can be a brilliant yellow color. In Mexico, it is gathered at night when the plasmodium is active and eaten like scrambled eggs! However, this mass shortly develops into a hardened structure called an aethalium, which holds large amounts of dusty spores. At this stage, it appears as if the neighbor dog lost his lunch near your petunias.
There is absolutely nothing that could or should be done to chemically control slime molds (or mushrooms) in the landscape. If the sight of "the blob" offends you on turf, simply water the organism off the turf leaves. Removing or eradicating slime molds from your mulch is an arduous task, so just cover it up with surrounding mulch. Or learn to appreciate them, because there is certainly no need to be as afraid of them as Steve McQueen was.
Fungus Among us