Issue 7, July 16, 2021
Not Your Household Vinegar
Do you find that social media opens up a lot of “how to’s” or DIY’s on weed control? Vinegar comes up often as an herbicide. In truth, vinegar does work as a herbicide, but not your average household vinegar. Most household vinegar solutions are at 5% acetic acid, where a herbicidal vinegar will have a range of 10-30% acetic acid. These higher percentages are more effective in controlling new seedlings and growing points than the household vinegar.
What is Vinegar?
If we look up the definition of vinegar, we find that it an aqueous solution of acetic acid. (Basically water with acetic acid) Acetic acid is a colorless, clear, liquid with a pungent odor. This pungent odor is the how we identify the smell associated with vinegar. The basic process of which vinegar is made is through anaerobic fermentation.
How does it work?
Vinegar is nonselective herbicide that can rupture plant cells therefore damaging plant material. Desirable plants need to be protected from potential spray drift. Acetic acid destroys cell membranes that can result in the desiccation of the plant tissue and eventual death of the plant. Unfortunately, it is not a systemic herbicide, and so coverage is critical and complete application of growing points is a must in order for it have the most efficacy. It is a fast-acting herbicide, where damage can be seen as early as 4 hours after application. There is also no residual activity with acetic acid, so multiple applications may be necessary.
Acetic acid has been found to be more effective on seedlings and annuals than more mature plants or perennials. It even has had effectiveness on plants like palmer amaranth that have been found to be resistant to many other classes of herbicides. Studies have shown that for vinegar to be most effective, the percent of acetic acid should be 10 to 30%. It can provide 80-100% control of weed species depending on the weed’s size, maturity, or life cycle.
Be sure to check out these studies on Acetic Acid herbicides.
https://ecommons.cornell.edu/handle/1813/46234, https://pdfs.semanticscholar.org/7ef8/b8090d113716b3635a1e4183e20fc71e9232.pdf, https://journals.pan.pl/Content/114662/PDF/OA_10_JPPR_59_4_385_Rl-Metwally.pdf
Even though it is nonselective herbicide some species differ in susceptibility. Broadleaf plants tend to be more susceptible than grasses. This can be due to the fact that the growing point is above ground vs under the ground. The waxier the cuticle more applications will be necessary, which is why it is important to treat plants as seedlings or with no more than 2-4 leaves.
We might want to think that vinegar isn’t harmful since we use vinegar on our salads and it is considered organic. However, stronger forms of vinegar can be hazardous to humans. Acetic acid concentrations over 11% can cause burns upon skin contact. In fact, eye contact can result in severe burns and permanent corneal injury. This is why reading and following the label is so important. Acetic acid is toxic and can be hazardous if used without taking precautions. It’s important to note that unless the product you are using for weed control is registered with the EPA as a herbicide, its use is illegal and a violation of FIFRA. Registered herbicides come with label directions, including use rate and required PPE (personal protective equipment). For more information, consult with the product label.
Resources
http://msuinvasiveplants.org/extension/monthly-weed-posts/2021-june-does-vinegar-kill-weeds.html
http://hyg.ipm.illinois.edu/pastpest/200714f.html
https://newcropsorganics.ces.ncsu.edu/2013/08/acetic-acid-vinegar-as-an-herbicide/
Author:
Maria Turner