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4-3-03
Conquer Weeds with Vinegar?
If fighting weeds in your garden has you in a pickle, you'll be interested
in a USDA research report about using acetic acid (vinegar) as an herbicide.
USDA researchers confirmed that acetic acid is effective at killing some
common weed species, including Canada thistle, lamb's-quarters, giant
foxtail, velvetleaf and smooth pigweed.
Weeds were hand-sprayed with various solutions of vinegar, uniformly
coating the leaves. The researchers found that 5- and 10-percent concentrations
killed the weeds during the first two weeks after emergence from the soil.
Older plants required higher concentrations of vinegar to kill them. At
the higher concentrations, vinegar had an 85- to 100-percent kill rate
at all growth stages. However, perennial weeds, such as Canada thistle,
were only temporarily knocked back; the roots survived to sprout new shoots.
Even though vinegar is an acid, it breaks down quickly in the soil and,
therefore, is not likely to accumulate enough to affect soil pH for more
than a few days.
Corn is the only crop thus far that USDA scientists have reported on
the use of vinegar to control weeds without harm to the crop. Vinegar
causes a rapid burn to plant tissue of susceptible species, so unintended
injury is quite likely without knowing more information. Further studies
are needed to know whether other crop plants and ornamentals can tolerate
the vinegar.
Ordinary household vinegar is about a 5-percent concentration. Stronger
solutions that are labeled for use as herbicides are now available from
some retailers, including http://www.sumrset.com/new_herbibide.htm,
http://www.greensense.net/,
http://www.bradfieldorganics.com/ and http://www.biconet.com/lawn/burnout.html.
Note that vinegar with acetic acid concentrations greater than 5 percent
may be hazardous and should be handled with appropriate precautions. Vinegar
solutions of 11-percent strength can cause skin burns and eye injury.
Also note that the use of a vinegar product for killing weeds, unless
the material is specifically labeled as a herbicide, is illegal and a
violation of federal pesticide laws. Always read and follow all pesticide
label directions.
More information about the USDA study is available online at http://www.ars.usda.gov/is/pr/2002/020515.htm.
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