Common Vinegar may be Potent Herbicide

WASHINGTON - May 15/02 - SNS -- Limited trials using solutions containing 20% vinegar by the USDA found between 80% and 100% of weeds in corn fields could be killed without harming crops.

Stressing more study is needed, USDA ARS researchers Jay Radhakrishnan, John R. Teasdale and Ben Coffman in Beltsville, Maryland have found vinegar is especially effective on Canada thistle, but also kills common lamb's-quarters, giant foxtail, velvetleaf, and smooth pigweed.

Only using vinegar made from fruits or grains, to conform to organic farming standards, the researchers estimate the cost of spraying an entire field is about U.S. $65 per acre in the United States. If applied to local weed infestations only, such as may occur in the crop row after cultivation, it may only cost about $20 to $30.

Some home gardeners already use vinegar as a herbicide, and some garden stores sell vinegar pesticides. But no one has tested it scientifically until now.

In their tests, the researchers hand-sprayed the weeds with various solutions of vinegar, uniformly coating the leaves. The researchers found 5% and 10% concentrations killed the weeds during their first two weeks of life. Older plants required higher concentrations of vinegar to kill them. At the higher concentrations, vinegar had an 85% to 100% kill rate at all growth stages. A bottle of household vinegar is about a 5% concentration.

Canada thistle, one of the most tenacious weeds in the world, proved the most susceptible; the 5% concentration had a 100% kill rate of the perennial's top growth. The 20% concentration can do this in about 2 hours.