acid (vinegar) for weed control revisited
by Micheal D. K. Owen
July 8, 2002 - A recent article in the Integrated Crop Management Newsletter (“Organic weed management workshop on July 1” [IC-488 (11), page 91]) describing the use of vinegar as a tool for controlling weeds prompted a number of questions from growers and agribusiness personnel in Iowa. As a result of these questions, I contacted the USDA researchers that conducted the work and also checked a number of sites on the Web for information. The information below is from discussions with the researchers Dr. John Teasdale and Dr. Jay Radhakrishnan, and publicist Don Comis, and is reported at several world wide web sites (www.barc.usda.gov/anri/sasl/vinegar.html and www.ars.usda.gov/is/pr/2002/020515.html ).
It is important to recognize that the use of acetic acid (vinegar), unless the material is specifically labeled as a herbicide, is illegal and a violation of FIFRA. A number of companies have registrations for acetic acid to be used as a herbicide. This information can be accessed at www.garden-ville.com, www.greensense.net, www.bradfieldind.com, and www.biconet.com.
Various lawn and garden stores may carry these products. Like any herbicide, it is important to follow all directions and safety procedures. The USDA issued a warning in their research report stating; “WARNING: Note that vinegar with acetic acid concentrations greater than 5% may be hazardous and should be handled with appropriate precautions”. However, acetic acid is not reported to accumulate in the environment and readily breaks down to water. Interestingly, 24% acetic acid apparently can temporarily decrease soil pH.
Acetic acid is not a selective herbicide. Dr. John Teasdale suggested the mechanism of action of acetic acid is similar to that of paraquat in that acetic acid causes the rapid dissolution of cell membrane integrity resulting in the dessication of foliar tissues, and ultimately plant death. Acetic acid is non-selective, and may damage any plant part contacted by the material.
While acetic acid may burn off the tops of Canada thistle and other perennials, it will not control the root system responsible for regeneration of plants. Furthermore, acetic acid may not control larger weeds. A recent demonstration at the Nashua Research Farm suggested that acetic acid is not effective at controlling larger weeds.
Directed applications (keeping the vinegar away from the crop plant) are necessary to use acetic acid when crops are present in fields. Acetic acid concentrations from 10 to 20% controlled 80 to 100% of the smaller weeds, as reported in the USDA release. Typical concentrations of acetic acid in most commercially available vinegars are 5%, and were reported to provided variable control of small weeds.
The USDA researchers suggested the spot spraying at the base of corn might be the most effective manner to utilize acetic acid as a herbicide. Broadcast applications of 20% and 30% acetic acid solutions would cost approximately $66.00 to $99.00 per acre, respectively. Banded applications could reduce that cost to one third of the broadcast rate.
Prepared by Micheal D. K. Owen, extension weed management specialist, Department of Agronomy, Iowa State University
more information contact:
ISU Extension Agronomy
2104 Agronomy Hall
Ames, Iowa 50011-1010
Voice: (515) 294-1923
Fax: (515) 294-9985
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