BELTSVILLE, Md. – 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.
Agricultural Research Service scientists have offered the first scientific evidence that it may be a potent weedkiller that is inexpensive and environmentally safe – perfect for organic farmers.
Vinegar solutions. Researchers Jay Radhakrishnan, John Teasdale and Ben Coffman tested vinegar on major weeds – common lamb’s-quarters giant foxtail, velvetleaf, smooth pigweed and Canada thistle – in greenhouse and field studies.
They hand-sprayed the weeds with various solutions of vinegar, uniformly coating the leaves. The researchers found that 5 percent and 10 percent 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 percent to 100 percent kill rate at all growth stages.
A bottle of household vinegar is about a 5-percent concentration.
Canada thistle, one of the most tenacious weeds in the world, proved the most susceptible; the 5 percent concentration had a 100-percent kill rate of the perennial’s top growth. The 20 percent concentration can do this in about 2 hours.
Crop use. Spot spraying of corn fields with 20 percent vinegar killed 80 percent to 100 percent of weeds without harming the corn, but the scientists stress the need for more research.
If the vinegar were sprayed over an entire field, it would cost about $65 per acre. 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.
The researchers used only vinegar made from fruits or grains to conform to organic farming standards.
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