Salt, Vinegar, and Glyphosate

I’ve been asked quite a few times over the last several years about a “homemade” herbicide recipe that is floating around the web. Many of you have probably seen it posted to Facebook or Twitter or Pinterest, or on your favorite home gardening site. One of my favorite descriptions calls it a “magical, natural, weed killing potion.” The recipe is largely the same regardless of the source. There are a pretty wide variety of claims about its safety, effectiveness, and “naturalness” depending on the website. One site even says it is “an alternative to chemical weed killers.” [Spoiler: it contains chemicals.]

imageThe recipe is nearly always a subtle modification of:

  • ½ gallon of vinegar
  • ½ cup of salt
  • 2 tablespoons of dish soap

Vinegar contains acetic acid, a chemical (yes, a chemical) with well-known herbicidal properties; it is commonly used by organic gardeners and farmers as a herbicide. The knowledge that salt (sodium chloride, usually) has herbicidal properties goes waaaayyyy back. Soap (even soap is a chemical) is added to increase the spreading of droplets on the weed leaf surface. Most commercial herbicides also contain soaps for this purpose, although we usually refer to them as “surfactants” in that context. The combination of acetic acid, salt, and soap will certainly kill many annual weeds, especially if applied when the weeds are small.

The question I get most often about this homemade 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.

Effectiveness

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). So if you don’t get complete coverage of the plant leaves with the vinegar + salt solution, there is potential for the plant to re-grow from the living tissues. Coverage with glyphosate is less crucial, since the herbicide molecule will travel to parts of the plant that were not sprayed.

This difference between systemic and contact herbicides is very important in how to best use each product. Because glyphosate travels through the plant, it can control perennial weeds, such as Canada thistle and quackgrass. The vinegar + salt solution, since it doesn’t move throughout the plant, will not be effective on perennial weeds. It will burn off the top growth of perennials (which may be desirable), but it will not provide long-term control.

The contact nature of the vinegar + salt mixture can be a benefit, though. If you need to kill weeds in close proximity to a desirable plant (say, killing chickweed in a flower bed), then glyphosate can be problematic. Only one or two stray drops from the glyphosate spray bottle onto a flower might be enough to kill the entire plant. A few stray drops of the vinegar + salt solution, on the other hand, will probably cause a little speckling but won’t kill the desirable plants. The exception would be if you continually spray salt in the same area, you can end up with too much salt in the soil, and that will damage nearly all plants. Acetic acid and glyphosate break down rather quickly in the soil, and so won’t cause any long-term soil problems.

So there are certainly some scenarios where the homemade herbicide mixture might be preferable to glyphosate for practical reasons. Comparing effectiveness between the two herbicides is difficult; they both have a potential fit depending on the situation. But what about the “inexpensive” and “safe” claims? I did a little homework to see how the homemade herbicide mixture compares to glyphosate with respect to cost and toxicity.

Cost

For costs, I went to Walmart and checked prices for vinegar, salt, and soap.

Walmart prices: Price to make up 1 gallon of spray:
Heinz White Vinegar, 1 gallon = $2.82
Morton Table Salt, 26oz = $0.72
Dawn 24 fl oz = $2.63
1 gallon vinegar = $2.82
1 cup salt (0.6 lbs) = $0.27
4 tablespoons soap (2 fl oz) = $0.22
 Name brands: $3.31/gallon
Great Value vinegar, 1 gallon = $2.38
Great Value salt, 26oz = $0.42
Great value soap, 24 fl oz = $1.97
1 gallon vinegar = $2.38
1 cup salt (0.6 lbs) = $0.16
4 tablespoons soap (2 fl oz) = $0.16
 Walmart brands: $2.70/gallon

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; there were always other herbicides included ranging from triclopyr (for woody species and vine control) to diquat (for quick burndown) or iGlyphosate-based herbicidesmazapic (for long-term residual control). 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.

Toxicity

For the toxicity comparison, I only looked up the mammalian toxicity values for glyphosate, acetic acid, and salt. Rat acute oral toxicity values and rabbit acute dermal toxicity values for all three chemicals are summarized in the following table. The toxicity values are presented in mg of material per kg of body weight of the test organism. The LD50 is the dose of the chemical that would kill 50% of the test population; in this case rats dosed orally or rabbits dosed on the skin. Low LD50 numbers mean higher toxicity.

glyphosate

acetic acid

salt (sodium chloride)

– mg/kg –

– mg/kg –

– mg/kg –

rat oral LD50

5,108

3,350

3,000

rabbit dermal LD50

>2,000

1,060

>10,000

In both toxicity measures, acetic acid is more toxic than glyphosate. Salt is more toxic to rats compared to glyphosate when exposed orally. The dermal toxicity numbers are a little more difficult to interpret, since for both glyphosate and salt, the values are listed as greater than a value. This typically means that the experimenters did not kill enough of the test rabbits at the highest doses used in the studies; so we know that glyphosate is safe at least up to 2,000 mg/kg and salt is safe at least up to 10,000 mg/kg. But we can determine from this data that acetic acid is more toxic than both glyphosate or salt. Pound per pound, glyphosate actually appears to be less acutely toxic to the mammalian test organisms compared to acetic acid or salt.

But this is only half the story with respect to toxicity. To estimate the actual risk of these products, we need to know not only the toxicity, but also the use rate; the dose makes the poison. Even highly toxic substances can be used safely if the dose is sufficiently low, and seemingly safe chemicals can be problematic if the dose is too high.

To figure out the actual risk, we need to calculate the amount of the toxic substances being applied. Most distilled white vinegar is 5% acetic acid (50 grain). At this concentration, one gallon of the homemade mixture would contain 6.4 fluid ounces of acetic acid (the active ingredient). One gallon of acetic acid weighs 8.74 lbs; so 6.4 fluid ounces would weigh 0.437 lbs; so there is 0.44 lbs of acetic acid per gallon of homemade mixture. To convert this to similar units as the LD50 values, 0.44 lbs equals 198,220 mg.

Eliminate Grass & Weed Killer contains 3.7 lbs of glyphosate acid per gallon; or 0.0289 lbs glyphosate acid per fluid ounce. At the higher labeled rate of 2.5 fluid ounces of product per gallon, there would be 0.07 lbs of glyphosate acid per gallon of mixed product. Similarly converting this to the same units as the LD50 values, 0.07 lbs equals 31,751.5 mg. So it appears that glyphosate, the less toxic chemical, is being applied at a rate 6-times lower compared to acetic acid.

Let’s do one more calculation to put these toxicity numbers into perspective. Male rats can weigh up to 500 g, or 0.5 kg. One gallon of the homemade mixture contains 198,200 mg of acetic acid, or approximately enough to kill 59 rats, if administered orally. One gallon of mixed glyphosate solution contains 31,752 mg glyphosate, or enough to kill 6 rats. The acetic acid in the homemade mixture is nearly 10 times more lethal than the glyphosate in the Eliminate mixture. And this doesn’t include the 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. For example, sodium chloride, one of the ingredients in the homemade herbicide solution, is mutagenic for mammalian somatic cells and bacteria. Another ingredient, acetic acid, is highly corrosive, can aggravate respiratory disorders, and even cause permanent vision loss. Does this sound like something you want to be spraying in the same yard where your children and pets play? Should you be dousing your yard with a potent chemical cocktail that causes mutations in humans and causes blindness? And now we learn that this chemical cocktail is nearly 10 times more lethal to mammals than glyphosate, one of the most potent weed killers on the planet! If you’re less scrupulous about your sources, you can even find links between acetic acid and a multitude of disorders, including eczema, psoriasis, shingles, and herpes. You read that right; THIS HOMEMADE HERBICIDE MIXTURE MIGHT GIVE YOU HERPES!

Maybe you’re not worried about the safety aspect; you simply don’t want to purchase Roundup because you dislike Monsanto. Well, don’t forget that vinegar is often made from corn, and most corn in the US has the Roundup Ready trait (which was developed by Monsanto). So the vinegar you are using to spray your weeds is probably made from corn that was sprayed with glyphosate: the very herbicide you were trying to avoid.

What does it all mean?

All joking aside, the important thing to keep in mind is that both the homemade vinegar + salt mixture and Roundup are pretty darn safe when used properly, they’re both relatively inexpensive, and both can provide effective weed control in the appropriate situation. Now, all this discussion has made me hungry for some Roundup Ready sweet corn, with just a little salt, and a salad with a nice vinaigrette dressing.

Comments

  1. Ha ha ha ha! That was excellent.

    And now–for a terrific student project: I would love a young student to do a bit of tissue culture, and replicate the Seralini protocol of pouring-stuff-on-cells studies. I would bet $10 the homemade product has negative consequences for tissue culture cells. But it would be fascinating to see the comparison.

    1. How about chlorine in swimming pools? I wonder what would happen if you exposed naked cells to that. Yet we let kids literally swim in chlorine solutions. A Seralini type study would prove that I should have been dead by age 10.

    1. I would have believed the ‘harmless’ approach until I read Mercola’s site with evidence that glycosate (used in Roundup) causes breast cancer, deformities and miscarriages. See example in Argentina (mercola.com). There’s a lot of money riding on glycosate.

      1. Hi Ronald- Mercola sells products too, and his chief sales pitch is to fearmonger. If you want to get an objective analysis on Roundup, read Cornell University’s Environmental Impact Quotient for Roundup: it is ranked around 15. That’s incredibly safe, organic sulfur is 45 and organic copper sulphate is 64, so the organic pesticides are much more harmful than most of the new synthetic pesticides. Progress! Are you aware that Mercola, like Natural News, are anti vaccine nutcases promoting themselves with discredited ideas. Read the EPA’s LD50 on Roundup, which will give you more evidence of the safety of Roundup. Or the MSDS. These are the standards used to evaluate Roundup, and are based on a extensive number of university, government and industry studies. Roundup is used in “no till” farming, and is an important tool to reduce global warming and increase soil quality.

        1. Round up is anything but safe and who cares about Cornell. They have proven it’s correlation to breast cancer and autism. Round up does nothing for soil and it decreases production by 35% over a five year period. It is poison. Time will tell on this one but if you believe anything that the EPA says about something that it has approved you are silly. It costs over 500,000 to just begin to get an approval for something from the EPA. It is not interested in approving anything natural for it’s so called approval. There are so many toxic substances on their approval list it is scary.

          1. I care what scientists say, especially those at land grant universities like Cornell, who have the public trust on their shoulders, and their paychecks paid with the assets set aside around the turn of the century when our government decided that our country needed first rate research in order to progress, that’s how MIT, UC Davis, U of Texas, Cornell got their money. We have an incredible academic system with absolutely dedicated people. There is considerable oversight by peers, and information is transparent. The Cornell EIQ system is a good way to compare pesticides. Mercola and Natural News sell quackery and answer only to their own bank accounts.

          2. If you read the study linking glyphosate to breast cancer, you will realize that thee authors specifically caution that they found it had an impact on the growth of cells that were already cancerous, and they also warn that an experiment in a Petri dish is much different than human consumption. You consume many carcinogens every day. At least three commonly used organic pesticides are carcinogenic: rotenone, copper sulfate, and pyrethrin.

            1. Dear Rita- I have been using glyphosate in my fields for 7 years and the last two years my harvests have been huge- so glyphosate does not reduce yields by 35% at my farm. It does help me reduce my greenhouse gas emissions from my farm by killing weeds without the harm to the soil and climate that tillage causes. Tillage is bad in many ways. And lastly, it seems odd that glyphosate causes autism AND cancer yet nobody at the EPA knows this? It’s not on the label. No one is reporting this. Are you being through in your research?

  2. Thank you for this article! I love seeing information about toxicity of common substances that most people consider “natural” or safe to consume.

  3. I don’t think LD50 is a particularly useful measure here. The concern isn’t deaths by acute toxicity, it’s about other effects on health and ecosystems. Salt is a nutrient and acetic acid common in food at low concentrations. Is glyphosphate similarly benign at such concentrations? LD50 alone isn’t enough data to be sure.

    1. i suppose you missed the part in the article where it says that salt stays present in the soil structure longer than glyphosate?? and the part that said high salt levels can actually prevent future plant growth??? whereas roundup breaks down quickly in the soil not disrupting future plant growth…

        1. Chris is right: glyphosate is a genotoxin, which means it has the potential to mutate genes over time. LD50 simply refers to how much could kill you in the moment. It has nothing to do with substances that can accumulate over time, or mutate genes, and cause disease later on. http://www.sigmaaldrich.com/MSDS/MSDS/DisplayMSDSPage.do?country=US&language=en&productNumber=45521&brand=FLUKA&PageToGoToURL=http%3A%2F%2Fwww.sigmaaldrich.com%2Fcatalog%2Fproduct%2Ffluka%2F45521%3Flang%3Den

          1. Genotoxin? Roundup? The reference could be to the tadpole study which used Roundup. Roundup contains surfactants, soap. I suspect soap is not recommended for tadpoles, so is the problem more rightly with the surfactant in Roundup rather than the glyphosate in Roundup?Isn’t this tadpole study an unusual testing ground for Roundup?

          2. Toxic and genotoxic effects of Roundup on tadpoles of the Indian skittering frog (Euflictis cyanophlyctis) in the presence and absence of predator stress.

            AuthorsYadav SS, et al. Show all Journal
            Aquat Toxicol. 2013 May 15;132-133:1-8. doi: 10.1016/j.aquatox.2013.01.016. Epub 2013 Feb 8.

          3. It seems you and Chris are both wrong…

            http://www.ncbi.nlm.nih.gov/pubmed/3286348
            An evaluation of the genotoxic potential of glyphosate

            _No genotoxic activity was observed in the assays performed. The data suggest that glyphosate should not pose a genetic risk to man._

            Another study saw cytotoxicity in high doses related to amphibians, no mention of genotoxicity.

            http://onlinelibrary.wiley.com/doi/10.1002/em.21775/abstract

            There is a focus on amphibians related to glyphosate, but as another commenter mentioned, the surfactants seem to be the culprit behind the toxicity affecting those amphibians.

            http://onlinelibrary.wiley.com/doi/10.1002/jat.2997/full

            Again, another study that finds no genotoxicity at suggested levels.

            http://www.ncbi.nlm.nih.gov/pubmed/23480780

            Now, this is not to say that given at doses much larger than what is considered safe couldn’t in fact cause genotoxic or cytotoxic damage, but that’s fairly understood as the dose make the poison.

            Again, it seems the surfactant is more of a problem than anything.

    1. glyphosate breaks down fairly quickly in the soil. high salt accumulations can actually prevent future plant growth. soooo… yeah. there you go.

  4. Good article, well written, but.. I thought Incomplete. There are well known concerns about the commercial herbicides (i.e., glycophosphates) and the relationship to the Huge bee die-off. If unaware, bees are ESSENTIAL to the reproduction of our food supply (pollination). Again, it has been known-suspected for some time now that the catastrophic bee die-off is attributable to the ‘Roundup’, etc. Personally, until more is certain, I’ll pay a bit more, undertake a bit of a hassle and make the home brew.

    1. Hi Dan, Thanks for stopping by to comment, but there is no evidence that glyphosate is in any way responsible for widespread bee deaths. -AK

      1. Andrew, if I may ask a silly question:
        Is there any issue with how these various chemicals are metabolized or eliminated? Frankly, sure, you can die from consuming massive amounts of salt, but in general at normal doses your kidneys and sweat glands are going to pull it out of the bloodstream. Acetic acid via vinegar is, I assume due to it having a caloric content, metabolized, and from what I can find under the respiration of ethanol, acetic acid in the body metabolizes out to carbon dioxide and water. In other words, at low doses it appears those ingredients are absolutely harmless for long-term exposures.
        What happens to glyphosate in the body?

        1. That’s what an LD50 rating means. The vinegar, salt, and soap, has a higher mamalian toxicity than Glyphosate. And if you seem to be okay putting low doses of that in your body, you should be seasoning your food with Glyphosate, because it’s safer

          1. That is not an answer to the question. What happens to it? LD50 is about quantities of lethal doses, not the mechanism of the substance. It doesn’t incorporate the sum of long-term exposures. Basically, there’s an LD50 for everything. There’s one for water. Glyphosate either must get metabolized like the acetic acid, or biochemically osmosed chemically intact like the salt, or it stays in the body like residual lead or mercury or Teflon. Which is it?

            Let me put this another way: Salt and sugar and water have LD50s. No one would tell you to avoid ingesting any water and any salt. Tetramethyl lead has a LD50 for rats of 105mg/kg, which is 1/30th the dose of table salt. Does that mean it’s OK to eat 1/30th the amount of tetramethly lead that you eat in salt? Of course not. Therefore just because glyphosate has a lower LD50 dose, does not prove that it is healthier for consumption than table salt.

            My original question stands: what happens to glyphosate in the body?

      2. Andrew, actually there was a peer-reviewed field study last year by the Bee Informed Partnership (top bee health researchers from the USDA & academia) which found a strong link between bee deaths and the total pesticide burden in their pollen – herbicides, fungicides and insecticides. Glyphosate was a top contributors to pesticide levels in bee pollen and pollen containing glyphosate (in combo with other pesticides since all pollen had multiple pesticides) killed a high proportion of bees that ate it. So – not definitive, but not absolutely no evidence either.

        1. Hi Heather, I can’t seem to find the pesticide study on the Bee Informed website (after some perusing). Do you have a link to the study? I would be very interested in reading it. -AK

          1. Dude, chill. The NYT reported on a study, so I included the link rather than searching for the actual study. Commenting on the internet isn’t my full time job, so excuse me for being lazy.

            One of the commenters below has included plenty of links to scientific studies. Check it out if you’re so concerned.

      3. Andrew since the male rat weighs 0.5kg and LD50 is mg per kg of body weight, would you have to double your figures on rat fatalities. Your figures are based on a rat weighing 1kg. So if you take 198200 and divide by 3350 you get 59 fatality’s if the rat weighs 1kg. Would it be 118 at 0.5kg?

    2. Glyphosate has no affect on be health. Neonic’s which are found on seed treatments might but most studies are inconclusive.

    3. there is absolutely no reputable evidence anywhere suggesting that glyphosate kills bees. anywhere. doesnt happen. radio signals kill more bees than glyphosate. i kill more bees than glyphosate. keep spreading your lies and misinformation with no credible evidence to back it up.

    4. The bee die off can’t be pined to any one thing, I learned this the hard way, I parked my truck up wind of a very productive hive for approximately 20 mins while I worked on near by hives and collected walls. The diesel exhaust killed that hive in approximately 15 mins. I was parked about 25 foot away and left the truck idle. :( I think the point if this article is to point out moderation. If you apply to much of anything to anything there can be a negative effect.

  5. Glyphosate is extremely toxic and is being overused. The large chemical companies like Monsanto have designed their entire new GMO (Genetically Modified Organism) Corn and other crops to survive glyphosate being sprayed on them when they are planted. Millions of gallons is poured year after year and it is entering our food chain. The EPA is currently re-evaluating the use of glyphosate and many independent studies are showing the toxicity of the chemical: http://www.beyondpesticides.org/gateway/?pesticideid=37

    1. Hi Nick, your link to the Beyond Pesticides site is a perfect example of a group using factual information out of context to make a chemical, in this case glyphosate, sound really scary. I could just as easily say that acetic acid is extremely toxic (yes, more toxic than glyphosate) and that it too is overused. I mean, it is being applied to an extraordinary percentage of lettuce in the US. The EPA reviews all pesticides on a regular basis, and I expect glyphosate to be re-registered with little trouble. It is one of the most studied pesticides in existence, and has been repeatedly shown to be safe when used properly. -AK

      1. Hi Mindy, Glyphosate is both a herbicide and a pesticide; pesticides are products that kill any type of pest, including weeds, fungi, rodents, insects, etc. Your misconception is a common one, though.

        “Though often misunderstood to refer only to insecticides, the term pesticide also applies to herbicides, fungicides, and various other substances used to control pests.”
        http://www.epa.gov/pesticides/about/

      2. Also, if you wanted to sell the herbicide (pesticide) concoction (vinegar, salt, and soap) as a weed killer, you would need to get EPA approval and get a pesticide number and be added to the pesticide database. In fact… maybe Heinz company is attempting to do that right now!!! Their corporate lawyers and scientists are probably hard at work looking at the pros and cons of sullying the company’s name be selling a pesticide when they are known as a food company. They’ll probably have to create a subsidiary company marketing ‘natural’ pesticides… They will have submit all their internal findings (corporate funding!!!) to an EPA panel of experts, and if the research does no support what known effects these compounds have on all test items, they will be sent back to the drawing board to resubmit the proper tests or prove why the safety or dangerous effects of the new product was different than what expert review would have expected given the data presented… ;)

    1. The idea of chemicals made in the lab is that they generally aren’t released into the public domain until extensive safety testing (usually at the cost of a whole stack of “lesser” mammals, because no system is perfect) gets them approved. You can just dig natural chemicals out of a hole in the ground or squeeze them from whichever animal you want.
      Some excellent natural chemicals include copper sulfate, caustic soda, alcohol and benzene (and that’s without being facetious and bringing up things like venoms and neurotoxins, carefully developed by various living things to be as effectively toxic as possible). All of these natural chemicals are pretty dangerous if handled incorrectly. I let school kids use most of them (except benzene) but I wouldn’t feed them to anyone.
      I guess my point is that “natural” does not instantly mean “safe” and “made in a lab” does not necessarily mean “will destroy you and all you hold dear”. Moderation in short and long term exposure are generally the key to dealing with even natural chemicals.

    2. Do you have any idea how acetic acid is made? In huge factories from natural gas. The direct precursors are methanol (highly toxic) and carbon monoxide (highly toxic). The source of a chemical (synthetic vs natural) is a false and meaningless comparison.

        1. David, Everclear would be ethyl alcohol.

          Methanol is mostly used in the production of other chemicals and is highly toxic. It is one of those things that will make you go blind.

          1. I used to work when I was young in a plywood factory (45 years ago). Once the sheets were sliced from the tree and dried a glue was applied to the wood and many sheets were glued together to make the various plywood thicknesses required. The glue was made out of various ingredients – one of which was methanol – it was mixed on demand so the ingredients were readily available to the workers. Around Christmas time, some employees decided to drink the methanol used for the glue. 2 died, a couple became blind. I was 16 at the time and totally shocked that even though all of the bottles had a skull and bones symbol on them they drank it anyway

      1. Our word “vinegar” comes from “vin aigre” which is French for bitter wine. I’m sure there is a lot of acetic acid being made from natural gas or other such industrial source materials, but most likely the acetic acid purchased as vinegar from a supermarket, even from a Walmart, is most likely just a grape product fermented well past any prime drinking age and then filtered.

  6. I would like to spray some weeds and I don’t want it to make my goats or chickens sick. I would think the homemade version is safer? Anyone know?

    1. Just a suggestion, don’t spray anything and let the goats eat the weeds. I bet hey would appreciate the diversity of diet.

      1. You may consider eating the weeds yourself, if they are an edible species. I recommend eating them after pouring over a light covering of acetic acid, sodium chloride, and vegetable hydrocarbons.

    2. Hi Anne, if you use a registered herbicide like glyphosate, the label will contain information on how soon it is safe to graze the area. For glyphosate, the grazing restriction can range from immediately after application to several days after application. Reading the label for the product you use is very important, for this and many other reasons. This is a disadvantage of the salt/vinegar/soap mixture (or any other homemade pesticide). Products that have not been evaluated as pesticides by the EPA/FDA are unlikely to have this type of information available. That said, I wouldn’t expect either glyphosate or the homemade mixture to cause any problems for goats or chickens. But it is important to read the label for any pesticide to be sure. -AK

      1. Boiling water (and steam with special equipment) can be used effectively to control small annual weeds. It will be similar to vinegar in that it will not control perennial weeds. And there can be safety concerns here, too, obviously. ;-)

      2. If you aren’t in a fire prone area, try one of those weed killing flame throwers. They obviously don’t control perennial weeds, but they do control small annual weeds in a very satisfying manner.

  7. Excellent analysis. I’ve blogged an attempt to address the “glyphosate is an antibiotic” myth http://controlledrelease.blogspot.co.nz/2014/05/glyphosate-isnt-antibiotic.html Up until I blogged this I was having I thought a good exchange of emails with a believer in the myth. Perhaps my poor writing, proof reading and grammar put them off. More likely they didn’t want to engage in a dialogue with someone who wants to discuss the subject rather than take their word without evidence as fact.

    Your excellent analysis will be a great resource for those of us who already know there’s no difference between natural and synthesised chemicals. But even better I think your article will set a few light bulbs off in others heads.

  8. I don’t cook with glyphosate, but I do cook and consume a considerable amount of naturally occurring plant pesticides. Many of the attributes of the foods we love are the chemicals which plants evolved to ward off pests. In addition, our spices such as mint, basil, oregano etc were not provided for our seasoning pleasure by a benevolent God or Goddess, but these humanly delightful toxins are there to discourage pests. But, as respects plants, always exercise care with the dose you consume since many common plants may be hazardous to your health if not prepared properly to neutralize the natural pesticides found within them.

    1. Hi Alicia, I followed your link to read up on these “hundreds of studies.” Although your article claims to have links to peer reviewed studies supporting the “dozens of serious health risks,” ZERO of the links you provided lead to actual peer reviewed studies. Two of them lead to press releases about peer reviewed research, but those are not even relevant to glyphosate (one is about benomyl, the other is about organophosphate insecticides). This is either very sloppy research, or an intentional effort to deceive.

  9. If it works with salt and vinger, why not?

    The alternative is manmade poison to the benefit to all other than health and nature.

    And remember, the only exact science is the “after the fact”

  10. Seems to me Andrew is on the take. Nice job buddy, enjoy your glass of water with some nice Round up Residue. I find it incredibly interesting that all the sources you quote (wait you don’t) but if you did would tie directly back to Monsanto. And I LOVE that you quoted the USDA and probably would the FDA as well Both organizations headed by former (and of course future) Monsanto execs. This article is complete trash. BTW – Try being a Monsanto farmer and then not. My dad would never switch and you know why? He knows that they would have “investigators” in his fields the very first year he quit to check for their genetics which would easily blow across the neighbors fields into his and pollinate with his non Monsanto corn, thus leading him down a very long legal battle at which time he would lose everything he has worked for his whole life.
    There are a billion reasons to hate Monsanto, and the only reports that show glyphosate is safe come from Monsanto sponsored studies. But by all means go ahead and gobble up their bull! My guess is you work for them!!!

    1. It’s a conspiracy, and we’re all in on it!

      I mean, you can’t prove to me that you’re not in the pay of evil corporates. Maybe you’re running a false flag operation to make environmentalists look like paranoid nutjobs? Maybe you’re in the pay of Big Organic, astroturfing to prevent any regulations from being put on their lucrative slice of the food industry? Maybe you’re just not very good at assessing studies and just get off on regurgitating fact-free talking points you picked up elsewhere?

      Who are you working for, Jason?

  11. If an ld50 experiment results in >2000 mg/kg, I would interpret this to mean 2000mg/kg was the highest dose tested and 50% lethality was not reached. 40% lethality might have been! we don’t know from this data. It just says that the true ld50 is likely to be higher than 2000mg/kg. just a technical point to improve your work. Read Chester Bliss for more. Otherwise not bad.

  12. You may be playing a little fast and loose with the LD50. “One gallon of the homemade mixture contains 198,200 mg of acetic acid, or approximately enough to kill 59 rats” Actually, it is really only enough acetic acid to be lethal to 50% of the rats. So only 24 rats would die.
    Other important questions would be the concentration of the acetic acid used in the LD 50 and the cause of death. Is it simply the acidity (H+) and not the acetate (CH3COO) casing the death? Would any acid, including glyphosate acid (sometimes known as 2-[(phosphonomethyl)amino]acetic acid), cause the same problems?
    But, it seems your goal is to provide an example of ridiculous, out-of-context use of scientific numbers to prove some preconceived notion. If so, you’re doing a good job.

    1. Sorry, due to an oversight, five more rats must die. The correct assumption is that 29 would die. (Really 29.5, but can you kill half a rat?)

  13. Thank you for your article. I’ve used plain vinegar on weeds, and it can’t completely kill the Canada thistle. I also have poured boiling water over the thistles which seems to kill better than the vinegar, but they have come back again. I am now probably going to buy some Roundup because of our thistle infestation. We went through a drought last summer, and the thistles moved in when the grass died. I do worry about our dogs and the birds in our area with the Roundup, but I will read the instructions very carefully before allowing the dogs out in the yard after application.

    1. I’m battling thistle at the nursery I work at. My experience here and in yards I’ve dealt with it are glyphosate works, but may take several applications. I will spray once, let the weeds dieback and then wait for new thistle to come up, then spray those when young.

      1. I’ve heard that slashing the thistles before applying the herbicide slightly increases the likelihood of effectively eliminating them, but I’ve had good luck without bothering.

      2. I have had some success getting rid of thistles by waiting until they flower, then cutting them down before they go to seed. Was told by a botanist friend that many are biennials and will regrow until they can flower, but then die. In areas where my timing is good, this seems to work. Completely natural, for those who care, but prone to the same challenges as the rhythm method;-)

  14. Thanks for such a great article, Andrew. All the response means you are on to something.
    I have been linking to this article every time someone posts the “natural herbicide” on facebook.

  15. How much did Monsanto pay you for arguing that their highly toxic herbicide is less toxic then salad dressing and soap?

  16. This is a very interesting thread of information. I just want to know if somebody has information on the effect of glyphosate to the microbial activity or population in the soil. I suppose this would have some implication specifically to the nutrient availability.

  17. Nice article….. couple of comments and a question. I’d agree that as far as commercially produced herbicides go RU is about as benign as its going to get, as you get products that work more selectively you get into nastier stuff but I’d worry more about acquired immunity to RU from excessive ag-wise more than I would about homeowner use. I’ve been using vinegar as a weed killer for years without adding the soap or salt for the most part and I still get results that Im quite satisfied with…. which leads to my question. Under the right circumstances… small annual weed on a nice hot day… I can kill a weed with about the same amount of vinegar as I might use to make a salad dressing…..are you suggesting that if I were to ingest the same amount of glyphosate it would have no ill effect?

  18. Here’s an easy question for you who claim that RoundUp is safe. Which would you rather have on your salad: vinaigrette dressing, or RoundUp? I’ll set a bottle of both on the picnic table and let you decide…

    1. You do know many companies make glyphosate now, right? The patent ran out 10 to 15 years ago. Professionally, the generic brands are way cheaper than the Roundup brand, which Monsanto still owns and is the name people know which is why you still see Roundup in stores.

  19. Thanks for the alternative viewpoint regarding Round Up. It makes me feel better about my sister using it all day long in her landscape business. For me, in my permaculture model, I would say three things. There are no “weeds” on my property, there are edibles and inedibles. The inedibles serve in three ways, erosion control, moisture retention, and soil amendment. And finally, nature supports life, all life, not just that life that I deem desirable or not desirable, so I trust nature and harmonizing myself with nature. So far, its working beautifully!

    1. One of our local organic farmers relies on Roundup. He has a locally famous carrot cultivar – it really is a great carrot – but it cross breeds with wild carrot, Queen Ann’s Lace. Needless to say, he’s more than glad to apply some herbicide rather than produce bad carrots.

    2. My neighbor lets his morning glories grow along his fence because they look nice (and he is lazy). However, morning glories are weeds because I don’t want them in my lawn. I intend for my lawn to be exclusively Kentucky blue grass because it grows thick which increases moisture retention. Morning glories leave bare ground which results in evaporation, meaning I have to use more water.

  20. I am constantly trying to get people to understand that “natural” and “organic” are not the same as “harmless”. Nice presentation of exactly that point! And just because it’s sold in a grocery store and you use it on a regular basis does not mean it’s safe either. This is all “use your head” stuff, but so many people don’t want to think about their worlds as anything other than black and white, for or against chemical…

    1. There is a ”nothing will ever grow there again” problem? Then what about the dreaded herbicide-resistant “super weeds” problem? Nothing will grow except when it does.

  21. Why is there a constant attack on glyphosate? There seems like a religious conviction that this product with a Cornell University Environmental Impact Quotient of 15 “must be bad”. I have seen nothing to conterindicate its use. Glyphosate should be considered a treasure to be guarded with the best Integrated Pest Management practices we have to prevent evolution from undercutting its effectiveness. Without care, all herbicides are rendered asunder by evolution. It’s benefit for no-till farming and reducing greenhouse gases is impressive. Especially compared to the excessive tillage and resultant soil structure destruction and fossil fuel use organic farms are stuck with to combat weeds.

  22. What an amazing discussion!! As a non-scientific novice, I read the article and found it counter-intuitive (deduction by I feel, rather than think). Then I skimmed the commentary and was alarmed, delighted, puzzled, and aghast. What I conclude is that there are so many variables and the interactions are so complex–both long- and short-term–that the answer to this specific questions: which is better homemade or commercial weed killer, is unknowable, or knowable only from a limit perspective. For more reasons than those of science. For the good of our planet and humanity and those who share this sacred ground with us, we need a better question that allows for the huge context humans have created, whose repercussions we are only beginning to glimpse.
    Nonetheless, this was a great stream of well considered ideas. Thank you.

  23. This article sounds like propaganda for Monsanto’s Round-Up. I would drink a mixture of vinegar (not made from corn) & pure natural salt…but, I wouldn’t drink a cup of Glyphosate!

  24. In all fairness, one factor you haven’t considered is residual toxicity, which would be zilch for vinegar. Glyphosate has been well-studied as to its environmental fate, and it is certainly one of the least toxic herbicides, but there are some concerns, such as its effect on mycorrhizal fungi, and I’m not referring to Huber’s fantasies. When I do see conflicting literature, as there is on glyphosate’s effect on mineral metabolism, my desire is for someone to look at all of it and explain the anomalies. It’s not always a case of “they’re wrong and we’re right,” it’s sometimes a case of unconsidered confounders.
    You might consider a link to http://www.intechopen.com/download/get/type/pdfs/id/25624, which is an extensive, fair review on glyphosate, published in 2012 as a chapter in “Herbicides – Properties, Synthesis and Control of Weeds”.
    A more recent variant on the vinegar weedkiller bandwagon is to include epsom salt (MgSO4 hydrate) as an ingredient.
    I regular joke about the vinegar bandwagon, and, in your de facto suppor of it, you ought to at least make this information on it available, since the hallucination is widespread that vinegar is highly effective against microbial pathogens. Being “natural,” it is conceived of, not just as “non-evil,” but also, automatically, as more effective at whatever you want it to do. See http://www.jstor.org/stable/10.1086/501694: “The natural products, vinegar and baking soda, demonstrated inadequate activity and therefore should not be used as home disinfectants.”
    Another place for information would be “Toxicity of Herbicides: Impact on Aquatic and Soil Biota and Human Health,” http://www.intechopen.com/books/herbicides-current-research-and-case-studies-in-use/toxicity-of-herbicides-impact-on-aquatic-and-soil-biota-and-human-health.

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