The question I get most often about this homemade herbicide mixture is “how does it compare to commercial herbicides?” In particular, how does it compare to Roundup (the trade name for many glyphosate formulations)? This question is especially relevant since several websites tout the mixture as a safe and inexpensive alternative to glyphosate.
The recipe is nearly always a subtle modification of:
- ½ gallon of vinegar
- ½ cup of salt
- 2 tablespoons of dish soap
Comparing the homemade mixture to glyphosate is difficult, because the situation will often dictate which herbicide is the better choice. If you are trying to kill small, annual weeds, I would expect the homemade solution to be as effective as glyphosate. The vinegar + salt solution will probably burn the weeds down faster than glyphosate, but glyphosate would likely work slightly better over the long term, especially on large weeds. The glyphosate molecule is systemic, that is, it will travel throughout the plant (even down to the roots) to effectively kill all plant parts. The vinegar + salt solution, on the other hand, works on contact primarily by disrupting the integrity of the cell membranes and desiccating the plant. It will not travel long distances through the plant (say, from one leaf to another).
It would cost approximately $3.31 to mix up one gallon of homemade herbicide, using prices from Walmart. This is using name-brand products available at most grocery stores; one could lower the price further by buying the Walmart branded products instead of name-brands. If I bought Walmart’s Great Value brands, the price would be reduced to $2.70/gallon. My local Walmart doesn’t sell a Roundup-branded product that contains only glyphosate. But there were several products that contained only glyphosate. A half-gallon of Eliminator Weed & Grass Killer Concentrate was available for $27.97. At first glance, this seems much more expensive than the homemade mixture; however, to mix up 1 gallon of spray solution, you only need to add 1.5 fluid ounces of the concentrated product. At that rate, the cost of the glyphosate solution is only $0.66/gallon. The label states that for “Tough Weed Control” you can mix up to 2.5 fluid ounces per gallon, raising the cost to $1.09/gallon. Even then, glyphosate is actually less expensive than the homemade mixture on a per-gallon, ready-to-spray basis.
For the toxicity comparison, I only looked up the mammalian (rats and rabbits) toxicity values for glyphosate, acetic acid, and salt. In both toxicity measures, acetic acid is more toxic than glyphosate. Salt is more toxic to rats compared to glyphosate when exposed orally. Pound per pound, glyphosate actually appears to be less acutely toxic to the mammalian test organisms compared to acetic acid or salt.
How could this be, you ask? Everything you’ve read on the internet says glyphosate is causing ailments from autism to obesity. How could glyphosate be less toxic than vinegar? Truth is, it is easy to make a chemical (any chemical) sound pretty nasty, even if you use verifiable, factual information.
Read the full, original article: Salt, Vinegar, and Glyphosate