The Dreaded Vomit Fungus
Also known as Slime Mold. And not to confuse the two, but while I’m at it, Lichens too …
During the past week I have had several calls about the “blobs” that tend to grow on mulch. When I call it “vomit fungus,” I can quickly confirm if I have correctly identified what they are trying to describe more politely. More politely, these blobs are also called slime molds.
I’m not going to get into the debate about whether these primitive organisms are actually fungi or protists. I’ll just concede that they are among the many organisms out there that have the function of contributing to the decay of organic matter. While their life cycle is a bit complex, they derive their nutrition from dead and decaying organic matter. And while they may grow up onto the stems or foliage of plants, they have no adverse effect on those plants beyond perhaps interfering with photosynthesis. Slime molds sometimes are quite colorful in shades of red, orange, or yellow but more often are duller shades of yellow to tan.
Another variety is also found on grasses and can concern gardeners but is not pathogenic. On grass the mold tends to look gray or smoky. A closer look shows tiny pustules on the grass blades in some shade of gray. It may tend to white, blue, or purple, but it’s usually a dull gray. Again, it is not a problem beyond the potential to interfere with photosynthesis.
What you should do with or about these things is probably nothing. But knowing how folks want to do something (and like to get out in the heat), the blobs in your mulch will probably go away more quickly if you break them up with a rake to speed drying. If you think it belongs in a plastic bag, so be it. In the grass, you can use a broom, rake, or stream of water to wash the pustules off the blades. In both cases, if you wait it out, it will probably go away in a few days.
You can see some ordinary pictures of slime mold at
http://www.coopext.colostate.edu/4DMG/Pests/slime.htm
Another perennial question involves lichens growing on plants. People usually associate the presence of lichens with dead plants or plant parts and assume a cause and effect relationship. That relation is a little tenuous. But if there is any cause/effect, it’s the dead plant material providing a substrate for the lichen and not the lichen causing plant death. We can observe lichens growing on rocks also but we don’t assume the lichen killed the rock.
Again, the taxonomists can argue classification; but in general lichens are symbiotic organisms composed of both an alga and a fungus. Each provides something for both of them: the alga provides carbohydrates and vitamins, the fungus water and minerals from the atmosphere. They usually appear in shades of gray, green, or white and with flat overlapping plates. As they develop they may become “fuzzy” and some can be brightly colored in shades of red or yellow.
While lichens may grow on plants, they seldom accumulate to any extent on healthy actively growing plants. Their presence on the bark of trunks and older limbs is normal. Younger stems that are actively growing should also be shedding bark as the stems enlarge. The shedding of bark prevents extensive accumulation of lichen. Once the growth slows or stops, then the lichen has opportunity to get better established. In that regard, lichens can be seen as a sign of slow growth or death but not the cause.
For more on lichens and slime molds, see
http://pubs.caes.uga.edu/caespubs/pubcd/B999.htm
alcooke
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Al Cooke
Extension Agent, Horticulture
Chatham County Center, North Carolina Cooperative Extension Service
N C State University
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email: al_cooke@ncsu.edu
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