Bright Yellow Slime Mold

2023 November 19

Sam and I were walking through the woods out back[1] on September 10, 2023 when we spotted this bright yellow growth on a dead branch lying on the ground. It was about the size of the palm of my hand, and looked a bit fuzzy.

It does not appear to be a fungus. Rather, the closest match I can find is “Dog Vomit Slime Mold, Fuligo_septica. Slime molds are related to the amoebas that we all learned about in school, the blobby microorganisms that move and eat by oozing around and engulfing food particles. This is the plasmodium stage, consisting of masses of amoeboid cells that have kind of fused together into one entity, and is now slowly crawling over and devouring rotting things on the forest floor. Those little projections are pseudopods that it is extending out looking for things to eat.

It doesn’t actually look that much like dog’s vomit at this stage. That comes later, when the whole mass stops moving and turns into a fungus-like fruiting body that generates spores. This then rots into a mass that is devoured by beetles, and the beetles then spread the spores around so the whole process can begin again.

When I was searching for information on this, the first two hits were:

How to get rid of dog vomit slime mold, and

How to grow and care for dog vomit slime mold

So, it appears there is a wide divergence of opinion on whether you want to kill this stuff, or encourage it. Personally, I favor the “encourage” option, but then you probably would have guessed that.

[1] Behind the 9 acres of land that we own, there is close to an additional two square miles of commercial forest land (which is open for access by the public), and surrounding that there is a snowmobile trail that is a pretty nice walking track. The only problem is that if I walk entirely on the snowmobile trail, the whole loop is about 6 miles long and sometimes I don’t have time to walk the whole way. So, Sam and I were looking to see if there was a good route we could take from the snowmobile trail through the woods back to our house, which reduces the length of the walk to about 3 miles. The first bit of the short-cut going through the woods is kind of steep, moist, and has a lot of interesting things growing in it, like this slime mold.

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