Reaching for a spray bottle is the standard reflex when a yellow blob turns up on your mulch overnight. The extension answer is a rake and a dry afternoon. No extension or herbarium source I reviewed has tested vinegar on slime mold. So I cannot tell you the vinegar slime mold trick works, and I will not tell you it fails on evidence nobody has gathered. What the research does back costs you nothing but a few minutes. Break the mass apart and dry it out.
A slime mold spray of any kind is aimed at the wrong organism, and the mismatch starts with basic biology. Slime molds are now known to be quite unrelated to the fungi, a point the UC Berkeley Museum of Paleontology makes flat out. Their cell walls carry no chitin. The Intermountain Herbarium at Utah State describes the spore walls as smooth, with cellulose in them instead. A product built to kill a fungus was never made with this organism in mind, and vinegar was never made for either job.
Slime mold chemical control is not something the extension services bother with, and the reason is practical rather than chemical. Michigan State's extension office says you may scoop the masses up to tidy a bed, and otherwise no control is warranted. That is the whole recommendation. There is no spray step hiding behind it, no product name, and no mixing ratio to get right, because the people who study this see nothing here that needs killing.
Hosing the blob off looks like the tidy version of the same job, and it is the one move the sources warn you about. Washington State's extension staff in Stevens County note that a strong stream does wreck the structure of the mass. It also spreads the spores over a larger area than you started with. You clear the patch you can see and seed the ground around it. Skip the hose and pick up a rake instead.
- Break: Run a rake or a stick through the mass until the structure comes apart.
- Dry: Leave the broken pieces spread out and exposed so they dry rather than sit damp.
- Scoop: Lift the masses out and bag them if the look bothers you, which is a tidiness step and nothing more.
- Skip: Leave the hose in the reel, since it carries the spores over a wider area than the blob covered.
The method itself takes one pass. UW-Madison Division of Extension says the best way to get rid of slime molds is to break them up and dry them out, and that is the entire protocol. You are not sterilizing anything or treating your soil. You are taking a damp, gathered mass and turning it into scattered bits that lose their moisture. A rake head does it, a stick does it, and a stiff broom over a hard surface does it too.
Every vinegar recipe you find online sits outside the research I reviewed. Mechanical removal is the only method these extension sources put their name to.
So what about the bottle already under your sink? I would leave it there. Not because vinegar has been shown to fail, since none of the sources I read ever put it in front of a slime mold. The vinegar slime mold question keeps coming back because the bottle is close at hand and the blob looks alarming. Untested is not the same as proven, and it is not the same as useless either. It is just unknown.
Give the mass a hard stir with a rake the next time one shows up on your bark or your lawn, then walk away and let the weather finish the job. Bag the pieces if you want the bed to look clean, and understand that you are doing it for your own eyes. The sources ask for nothing else. No spray, no fungicide, and no shopping trip.
Read the full article: Slime Mold: Not a Fungus, Not a Problem
