Organic farmers may have a new way to kill weeds

SALEM, Ohio – After your salad and fair fries, vinegar lingers on your taste buds.
But it may be deadly when it lingers on the bud of a plant.
Strange as it may sound, researchers are taking a careful look at whether household vinegar could help organic farmers deal with their weeds.
For Rafiq Islam, a research scientist at Ohio State University’s Ohio Agricultural Research and Development Center, his research began accidentally.
The experiment started when he had vinegar in a spray bottle; thinking it was water, he sprayed vinegar on some plants.
The plants he sprayed were dead within 48 hours.
Research. He then set up research plots to learn more about vinegar as an herbicide.
He experimented with three ways to kill weeds: mowing, spraying the herbicide Roundup, and using 4.5 percent acidic store-bought vinegar.
The annual weeds he experimented with were not affected by mowing them down, he said. They quickly came back up.
With Roundup, he found the weed dies and decomposes immediately. This means the nutrients don’t stay around to enrich the soil, he said.
But with vinegar, he found it not only killed the weed but it also allowed the plant to decompose slowly, acting as a mulch while its nutrients went back into the soil.
Varying results. Not everyone has had this much success with vinegar as a weed killer.
Several years ago, researchers from the USDA Agricultural Research Service also did studies on vinegar.
They wanted to find organically acceptable ways to kill weeds, said John Teasdale, a researcher with the service.
Household vinegar is not that effective because it isn’t strong enough, he said. The research service’s results showed 5 percent, store-bought vinegar is only marginal for killing weeds.
Instead, Teasdale found 10 percent or more acetic acid, at least double the concentration of store-bought vinegar, is needed to kill most vegetation.
He found that some herbicides do contain higher percentages of vinegar, but they also include other ingredients and are not labeled as strictly vinegar, he said.
Visibly wet. Using vinegar is most similar to Paraquat, an herbicide widely used in no-till farming, Teasdale said. The difference is vinegar must be sprayed to wetness and Paraquat can be sprayed by the acre.
Spraying the vinegar at a typical rate such as 30 gallons per acre was not effective.
The research service tried vinegar on perennial weeds as well.
They found it killed only the above-ground portion and had no affect on the root, allowing it to grow back.
Teasdale warned, however, that crops and weeds are equally effected, meaning it can also kill your crop.
Against the law. Regardless of whether vinegar works as a weed killer, Bill Pound of the ODA Pesticide Regulation Section, said not to use it.
“Technically, no, (vinegar should not be used) unless it indicates on the packaging it can be used as an herbicide,” Pound said.
There are many home remedies used by gardeners but that doesn’t necessarily mean they are approved by the ODA or USDA.
“Lots of things kill weeds. Gasoline kills weeds, but we wouldn’t want people to spread that on their gardens,” he said.
The ODA allows only products specifically labeled as herbicides or pesticides to be used on plants.
For a product to be used as an herbicide, it must have an EPA registration number. To obtain a registration number there are several hoops one must jump through, Pound said.
The product would then also have to be registered in Ohio.
Future trials. Meanwhile, Ohio State’s Islam is planning more research on vinegar this winter.
He would like to test what types of plants do best in the soil after being treated with vinegar, what kinds of weeds vinegar can kill, and what the vinegar will ultimately do to the soil.
More experiments need to be done to confirm his findings, Islam said, but for now he believes vinegar will kill any ground cover.