It sounds like the setup for a joke, but it isn’t.
More than 2,200 miles apart, two women walk into their local garden-supply stores. They find themselves similarly unsettled to find gallon bottles of “30 percent vinegar” displayed on the shelf among the herbicides.
Acetic acid, the active component in vinegar, can, in fact, help to subdue some weeds. Products from certain manufacturers — much stronger than the typical household vinegar concentration of about 5 percent acetic acid — are labeled for herbicide use.
The punchline, though: The ones these women saw, displayed prominently among the weed killers, weren’t labeled herbicides. Nor did the packaging include any instructions for using them safely and effectively in that capacity.
It was that omission, in particular, that made both women nervous. But only one of them knew the reason behind it.
Dr. Mangold’s work focuses primarily on larger landscapes and helping ranchers and public landholders like the U.S. Forest Service devise strategies for tackling invasive species.
“For those dealing with a very abundant invasive plant scattered over a large area, hand-pulling is impractical,” she said. “You have to weigh the risks of using an herbicide versus doing nothing — impacts such as lower biodiversity and other ecosystem effects.”
Herbicides, she said, may be the most effective method in those situations. But some unwanted plants, like an occasional dandelion in a lawn, are just unsightly, and don’t warrant spraying.
We need to differentiate between what Dr. Mangold calls “noxious weeds” and mere nuisance weeds — the ones it would be safest, and most economical, to pull, dig up or hoe. Or, when seeking a fresh slate in a whole garden bed, maybe solarize them under plastic sheeting, letting the sun do the work.
With Noelle Orloff, the weed and invasive-plant identification diagnostician at the university’s Schutter Diagnostic Lab, Dr. Mangold also trains Montanans on proper herbicide use. The two field a lot of backyard-weed questions from homeowners. Their takeaway: Many people use pesticides without much how-to knowledge.
“‘I’m trying to get rid of — fill in the blank,’ they tell us,” Ms. Orloff said. “And then they list all the things they have done so far to the weed, like spraying bleach on it.” (Bleach, should you be wondering, is not a substance that either expert would have recommended, had she been asked.)
integrated pest management, or IPM — “using a variety of tools and methods to control an undesirable organism,” Dr. Mangold said. “Which, in our case, means plants that are weeds.”
The IPM decision-making process that precedes any action aims to determine the least toxic solution possible to achieve tolerable levels of pest pressure, whether from weeds, insects or animals.
And if an herbicide proves to be part of a weed solution, “it’s all about maximizing the benefit while minimizing the risk,” Ms. Orloff said. “Because using any herbicide, organic or synthetic, has some level of risk.”
She and Dr. Mangold suggested that anyone tackling weeds get into the IPM mind-set by asking themselves several questions.
Do you know what the undesirable plant is? Without proper identification, it’s impossible to know the plant’s life cycle, including whether it is annual or perennial, which will inform any control strategy.
Do you have a weed that is susceptible to the treatment under consideration, and is it at the right life stage for effective treatment? Horticultural vinegar, for example, is recommended for use on young annuals that have four or fewer true leaves, not on established ones or on perennials that may suffer foliage damage but are likely to resprout from their roots.
With poison ivy or a deep-rooted perennial invasive like field bindweed (Convolvulus arvensis), Ms. Orloff said, “you might have to spray horticultural vinegar every two weeks for five years — not a feasible plan.”