If you're shocked to see a pile of yellow, foamy slime on your lawn, you might assume it is something disgusting left behind by a dog or other animal. In fact, it is most likely a patch of the common slime mold Fuligo septica, frequently called by the descriptive name "dog vomit fungus." Although there are many types of slime mold, the dog vomit fungus is one of the most easily identified, due to its distinctive appearance.
Slime Mold Description
Despite the name, the many varieties of slime mold are not molds or fungi. They are a family of simple organisms that are similar to amoebas. Many slime molds, including Fuligo septica, come together during one part of their life cycle to form a plasmodium, one enormous cell containing many separate nuclei. It moves slowly across your lawn, engulfing bacteria and fungi on the grass. Fuligo septica appears as yellow or orange foamy slime in the beginning of its reproductive cycle, but within a day or two begins to dry and harden into a crusty, gray or brown shrunken mass. This mass eventually breaks open, releasing millions of spores into the air and surrounding environment.
Slime Mold Causes
Dog vomit fungus is a very common organism found throughout most of the world. Fuligo septica grows on any type of grass and sometimes in flowerbeds or other planting areas. It is particular common on decaying wood, and many gardeners inadvertently introduce the organism to their yard by spreading wood chip mulch around their plants. The yellow slime often moves slowly out of the wood mulch and onto the grass. Slime molds grow and reproduce during cool, humid weather, though their spores can remain viable for many years.
Getting Rid of Slime Mold
Other than the unattractive, yellow slimy appearance, dog vomit fungus is not harmful, and you don’t need to remove it from your grass. The slime mold is not eating the lawn, but is devouring microscopic organisms it encounters during its slow travel. The yellow patch of Fuligo septica will disappear on its own, but if it bothers you, you can scrape it away with a shovel, or use a strong blast from the hose to melt it into the grass. The brightly colored stage only lasts a day or two, and the entire fungus will disappear within a few days, especially if the weather turns warm and dry. The spores will remain, however, and the slime mold is likely to reappear when humid conditions return.
Effects of Slime Mold
The ugly appearance of dog vomit fungus frightens many gardeners, who worry it might be hazardous to pets or humans. However, you don't need to be concerned, as Fuligo septica is harmless to both. In fact, Fuligo septica is cooked and eaten in some parts of Mexico. Spraying the organism with fungicide or other strong chemicals is more harmful to your health than simply leaving the slime mold to finish its life cycle. Occasionally, your grass underneath the patch of slime mold will yellow, but it will regain its normal color quickly once the plasmodium has moved on or dried into its dormant form.
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