Vinegar is proving effective in killing common weeds like Canada
thistle but it could be used more widely, says researcher Jay
Radhakrishnan.
A research agronomist with the United States Department of Agriculture
in Maryland, Radhakrishnan has received hundreds of e-mails about his
research team’s two-year-old study on vinegar herbicides.
He found that vinegar in acetic acid concentrations of 20 percent
killed thistle plants when applied directly to the roots. Household
vinegar contains five percent.
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The higher strength vinegar was also effective on numerous other weeds,
including lamb’s quarters, giant foxtail, velvetleaf and smooth pigweed.
Vinegar with five and 10 percent concentrations killed the weeds during
their first two weeks of life. Older plants required higher
concentrations to achieve an 85-100 percent kill rate at all growth
stages.
Radhakrishnan sees vinegar herbicide as a good alternative weed killer
for organic producers who cannot use conventional chemicals in their
crops. Researchers only used vinegar made from fruit or grain to
conform to organic farming standards.
He is now exploring its use in 15 crops, in treating weeds before and
after they emerge in various concentrations and studying what can be
added to vinegar plus how vinegar affects soil acidity. Two more years
of data are required, he said.
Vinegar shows promise as a nematicide and in destroying soil pathogens,
although Radhakrishnan declined to discuss those areas due to
intellectual property issues.
He cautioned that the higher concentrations must be handled carefully
as they can irritate peoples’ skin and throats. He advised wearing
protective clothing, masks and gloves.
Radhakrishnan began his research after noting how some people drink
vinegar to break down carbohydrates and help them reduce weight. As
there are a lot of carbohydrates in thistle roots, he thought vinegar
could work on them also.
When he poured vinegar on corn, the crop was not affected but a large
number of weeds were destroyed. Tests on other crops, such as soybeans
and wheat, were not conclusive, he said.
“As soon as it touches the root it seems to burn the roots out,” he
said.
Rough estimates peg the cost of vinegar herbicides at about $22-$32 US
an acre when selectively applied to areas such as bands between crop
rows.
Agriculture Canada reports no similar research being conducted in
Canada, but Marc Richard of the Canadian Pest Management Regulatory
Agency said there are four vinegar products registered for weed control.
First registered in 1999, the vinegar herbicides include three products
from Ecoclear of Oakville, Ont., and one sold under the President’s
Choice label.
Ecoclear offers the only one registered for commercial use and is sold
in 25 percent concentrations. The others, for domestic use and spot
treatments of weeds, are sold in six percent concentrations.
The commercial one is intended for use in spring and early summer to
control herbaceous broadleaf and grassy weeds in non-crop right of ways
and industrial land sites, he said. It is not intended for agricultural
use.
“It’s non-selective so it would kill your crop,” said Richard, who
noted corn might survive because it is hardy.
To register pesticides in Canada, he said manufacturers must first show
the product works without harming the crop it is trying to protect.
