BAR TODAY || Official Quarterly Publication of the Bureau of Agricultural Research

Vinegar: The effective weedkiller
by Rita T. dela Cruz

April-June 2002
Volume 4 No. 2

Vinegar is part of every household's kitchen but did you know that this sour-tasting liquid is an effective herbicide for organic farming?This is the major finding of a study conducted by Jay Radhakrishnan, John Teasdale and Ben Coffman, researchers from the Agricultural Research Service (ARS), the principal scientific research agency of the US Department of Agriculture (USDA). Although, a few farmers have already been using natural agents like baking soda, garlic and vinegar as herbicide, there were really no scientific studies to back-up that these agents are effective. Thus, scientists from ARS conducted greenhouse and field researches to determine the effectiveness of vinegar as herbicide.

To conform to organic farming standards, the scientists used vinegar derived from fruits (grapes and apples) or grains (malt). Naturally processed vinegar is produced by rotting the fruits or the grains under an anaerobic or "no-oxygen condition". Through fermentation, the sugars from these plant sources are converted to alcohol and carbon dioxide. Through oxidation, the alcohol reacts with air to form vinegar.

Vinegar that is prepared from plant sources contains 5% acetic acid, a pungent, colorless acid, which is basically the main component of vinegar. Acetic acid is commonly known as ethanoic acid.

The potency of this vinegar was tested on five major weeds, namely: common lamb's quarters, giant foxtail, velvet leaf, smooth pigweed and Canada thistle. Using the spot spraying method, the scientists hand-sprayed and uniformly coated the leaves of the weeds with different solutions of vinegar.

According to Dr. Jaay Radhakrishnan, lead researcher of this study, the vinegar was able to "kill several important weed species at several growth stages." He added that, vinegar with 10-20% acetic acid concentration killed 80-100% of selected annual weeds particularly, the 3-inch giant foxtail, 5-inch common lamb's quarters, 6-inch smooth pigweed, and 9-inch velvetleaf.

Results further showed that the 5% acetic acid concentration had different effects on the weeds. However, the Canada thistle, one of the most stubborn weeds in the world, was found to be the most receptive with 100% kill by 5% solution.

These weeds grow along with crops so it is important that the scientists also determine the effects of spraying vinegar to these major crops. The scientists spot sprayed the base of the corn rows and found that the vinegar was able to control 90-100% of the weeds while the corn plants remained unaffected. The scientists informed the farmers that they could also use the broadcast application (applying by scattering) of vinegar to their crops but the process is more expensive compared to band application (applying to a certain portion only).

Aside from being economical, using vinegar as herbicide is also environmentally safe. Farmers can now do away with synthetically processed herbicide that could affect their health.

Source: Press release at ARS News and Information, "Spray Weeds With Vinegar?" by Don Comis of the Agricultural Research Service, USDA, Beltsville, MD. For more information you may contact the lead researcher of this study through his e-mail, radhakrj@ba.ars.usda.gov.