A perennial problem: When dealing with weeds, homeowners and managers must decide what’s worse — the plants or the chemicals

Editor’s note: This is the third and final article in a series about weed control and management. The other articles were published in the April and June issues of the Four Corners Free Press.

“Every human being is now subjected to contact with dangerous chemicals from the moment of conception until death.” — Rachel Carson, Silent Spring (1962)

What’s more dangerous – a noxious weed or the substances used to kill it? That question has plagued homeowners, gardeners, farmers, and local government officials for years, and it still has no easy answer.

If we’re talking about just dandelions, the answer is simple – the weed killer is more harmful. Dandelions may be viewed as unsightly, but they don’t compromise human health. Indeed, if all you had to eat was a dandelion and you munched the entire plant – root, leaves, flower, stem and seed – you’d have all the nourishment needed for human survival.

But what if your pasture is full of Russian knapweed, one of Colorado’s “B” List noxious weeds? In that case, you are mandated by Colorado law to suppress and control the infestation.

The preferred plan includes both mowing and the application of Gordonor Milestone (carboxylic acid growth inhibitors). Dow, the manufacturer of Milestone, says it is “less toxic than table salt” and “practically non-toxic to birds, fish, honeybees, worms and aquatic invertebrates.”

However, you are warned against walking over areas that have recently been sprayed with the herbicide, and not to eat any berries treated with it.

The directions also advise you to wear coveralls, chemical-resistant gloves, shoes and socks; avoid spray drift; stay out of treated areas for at least 12 hours; and avoid using treated plant residues or manure from animals that ingested treated hay or forage in your compost.

Besides the knapweed, Milestone will kill alfalfa, cotton, dry beans, flowers, and other broadleaf or vegetable crops, fruit trees, ornamental plants.

In this case, it’s not easy to determine which is more harmful – the knapweed or the herbicide.

What are herbicides?

A simple definition for herbicides is that they are agents that destroy or inhibit plant growth. Herbicides are pesticides – substances used to destroy “pests.”

The category includes not only herbicides (weed killers), but insecticides (bug killers, including repellents), fungicides, rodenticides, antimicrobials (microbe killers including disinfectants), algaecides, molluscicides (killing snails, slugs and other mollusks) and even miticides (killing mites).

Name a “pest” and there is probably a substance developed to kill it.

Today, herbicides can be purchased online as well as at grocery, hardware and big-box stores like Walmart or Costco.

The products are readily available, but in order to avoid harm, they must be used according to their labels.

Tom Hooten, Colorado State University Extension agent for Montezuma County, said that for all herbicides, “the label is a legal document. The purchaser is required to use it according to the label.”

Similarly, the Montezuma County Noxious Weed Department has clearly highlighted in red and marked in bold “THE LABEL IS THE LAW” on the first page of its website.

What this means is that you have to adhere to the label’s instructions, and by doing so you assume all risk associated with the chemical. It also means that if you suspect an herbicide has not been applied correctly yet it has caused damage to your property or yourself, you can notify the Colorado Department of Agriculture’s Pesticide Division.

You may not receive any monetary compensation but your complaint will be investigated. However, neither the state nor the manufacturer will assume responsibility for any harm potentially caused by the product.

But how does the ordinary citizen know whether an herbicide can cause harm? This is tricky.

All chemicals are toxic

Herbicides have several modes of action. They can be broad-spectrum, like Roundup, or they can focus on one kind of plant while leaving others alone.

Most, including Roundup Ultra and Paraquat, work on both broadleaf plants and grasses. Others are selective only for broadleaf plants, such as 2,4- D and Gordon, while some target only grasses.

Application methods are essential to proper use of herbicides and are specified on the label. Weather conditions, including the time of day, are important, as rain may wash some herbicides off and into surface waters, while wind causes drift.

To help consumers sort this out, the EPA uses “signal” words on pesticide labels:

  • Poison – causes illness or death if ingested, especially when a low dose will kill;
  • Danger – causes corrosive-permanent or severe skin, eye, or respiratory damage;
  • Warning – causes moderate skin, eye, or respiratory damage, and small to medium dose causes death, illness, or skin, eye, or respiratory damage;
  • Caution – causes mild irritation, but at higher dose could cause death, illness, or skin, eye, or respiratory damage.

“The county weed program does not use any herbicides with the signal word poison,” said Bonnie Loving, weed manager for Montezuma County.

“A vast majority of the herbicides we use have either a caution or warning signal word.”

But she adds that any chemical can be poisonous. “All chemicals, if taken in a high enough dose, are toxic.”

Some herbicides are “restricted use” (RUP) meaning they are only made available through a licensed outlet, such as a farm co-op, to people with a private applicator’s license. In Colorado, these include any products that contain Bromacil, Diuron, Monuron, Prometon, Sodium Chlorate, Sodium Metaborate, and Tebuthiuron.

The primary herbicides used in Montezuma County are Roundup, Milestone and Gordon, according to Hooten.

Colorado law says noxious weeds must be either eradicated (List A), controlled and suppressed (List B), or recommended for suppression (List C). Montezuma County promotes the use of biological and cultural methods of weed control in addition to herbicides. Yet in many cases, pulling, mowing, burning, or allowing livestock to graze are not viable methods of weed control or eradication.

Many of the so-called noxious weeds are harmful to horses or livestock but cause no harm to humans.

However, weed killers can expose humans and some wildlife to increased health risks. What is the answer?

“As long as you use the herbicide in accordance to the label there will be no threat to the applicator’s health, animals, and or the environment,” Loving said.

But can we be certain? The debate is furious.

Herbicides in the environment

Lyn Patrick, a naturopath in Mancos, said that 2,4-D (an ingredient in Agent Orange) was sprayed on the town park with no signage to warn citizens to stay off the recently treated area.

According to the National Pesticide Information Center, 2,4-D has limited impact to humans, causing eye irritation, vomiting, diarrhea, headaches, kidney failure and muscle damage. In dogs it can cause vomiting, diarrhea, excessive drooling, lethargy or convulsions, and it is also toxic to fish and other aquatic life. The chemical is a common ingredient in many over-the-counter weed treatment products for lawns.

In Mancos, a citizen-based initiative prohibiting the use of Roundup in the town park was passed, and the town now posts information about what will be sprayed and when. Patrick, who lives less than a quarter-mile from the park, said she has been tested for glyphosate and her levels of the chemical have decreased since the town stopped using Roundup.

In Dolores, city parks aren’t sprayed at all, according to town staff, but infestations of noxious weeds along the river trail are sprayed, as mandated by state law. The county weed department provides the town with information about what needs to be controlled and where.

The City of Cortez contracts with Eddy Lewis of Southwest Weed Control to eradicate List A weeds such as knapweed (spotted and diffuse), cutleaf teasel and common tansy. Lewis primarily uses a selective agent, called Confront, available only for commercial use.

Mark Boblitt, Cortez Parks and Recreation superintendent, said public safety is paramount.

“We’re trying to be as safe as we can – we don’t spray haphazardly,” he said.

Two years ago the city applied allorganic fertilizers on city parks, and, according to Boblitt, is moving towards more organic and non-toxic methods of weed control. All areas sprayed are placarded, and both Boblitt and Dean Palmquist, Parks and Recreation director, said they try to keep people away from treated areas even longer than required.

“If the label says that it is safe to be in contact as soon as the spray dries, or in half an hour, we tell people to stay off for 24 hours,” said Boblitt. “We’re even more conscientious in the dog park – we close that for two days, but we don’t spray every year.” The city uses Landmaster, a nonselective herbicide, primarily around fence lines to spot-treat weeds growing at park edges. Placards notifying the public of the treatment are placed on all main park entrances three days ahead of time.

“I want people to be informed,” said Boblitt, “so they can make that decision themselves.” The EPA regulates insecticides, fungicides and rodenticides, but has no specific regulations for herbicides. The USDA has a pesticide data program, but does not test for residue of glyphosate – the main ingredient in Roundup, and the most widely used herbicide in the world. The USGS maintains a Pesticide National Synthesis Project website with links to maps of estimated herbicide use, by herb and by year, but none of this can determine human exposure. The Centers for Disease Control does not measure glyphosate exposure in either children or adults.

Accurate information about herbicides in the environment and their impact on human health is difficult to find. Research by Monsanto/Bayer and other corporate interests has found lower environmental levels of herbicide residue and little negative impact on human health, while many studies conducted by private, academic or activist organizations demonstrate a plethora of deleterious impacts on humans and the environment.

Increasingly, we are exposed to more and more of these substances, often without our knowledge. One exposure won’t harm us, but what about coming into contact with a chemical day after day, year after year?

Pesticides, including glyphosate-based herbicides, have proliferated in the environment since their use began over 60 years ago. Monsanto/Bayer first marketed Roundup in 1974.

In 1996, Roundup-Ready, herbicide-tolerant soybeans, corn and cotton were approved for use in the U.S. This meant that glyphosate could be used as a “broadcast post-emergence” herbicide, which significantly increased the amount used. Roundup also started being applied to crops post-harvest as a desiccant, increasing the shelf life of grains like wheat, barley and oats.

In Kansas, the annual use of glyphosate tripled between 1995 and 2012. Worldwide it has been estimated that over 9.4 million tons of glyphosate have been applied since 1974 – 1.8 million tons in the U.S. alone.

Other crops treated with glyphosate include sugar beets, wheat, barely, alfalfa, sorghum, oranges, canola, beans and cotton. Currently, herbicides containing glyphosate are used in over 160 countries, with the U.S., China, and Brazil applying the most. In the United States, more than 17,000 pesticide products are on the market.

Herbicide residue is not limited to agricultural fields or places that are treated directly. In addition to town parks and athletic fields, herbicide residue has been discovered in swimming pools, cosmetics, pet food, streams, lakes, tap water, farm animals, tampons, beer, and infant formula as well as human, rabbit, and cow urine.

The herbicide atrazine, linked to birth defects, infertility and cancer, is found in 94 percent of U.S. drinking water tested by the USDA, according to the Pesticide Action Network.

In 2017, the Organic Consumers Association found traces of glyphosate in Ben and Jerry’s ice cream. Glyphosate has also been found in Cheerios, Ritz crackers, gluten-free oatmeal cookies, hash browns, bagels, bacon, and a host of other products. It is even found in numerous organic products including unbleached flour, cream of wheat, soy creamer, hash browns and produce, although levels are significantly lower in organic products.

Public safety

People not only ingest food and water containing the chemicals, they breathe air polluted by their application. There is no doubt that the chemicals affect human health, but to what extent and in what ways remains controversial.

A study published in Environmental Health in 2016 found that glyphosate-based herbicides contaminated drinking water, were endocrine disruptors, and increased the risk of developing non-Hodgkin’s lymphoma. Other widely published research noted altered gene function and liver and kidney damage in rats exposed to amounts of glyphosate allowed in tap water in the European Union.

In 2015, the World Health Organization’s International Agency for Research on Cancer declared glyphosate a probable human carcinogen. This was used as evidence in a lawsuit against Monsanto filed by a man named Dee- Wayne Johnson with non-Hodgkin’s lymphoma.

Johnson applied Roundup up to 30 times a year in his job as a pest manager for a California school system. In August 2018, a San Francisco court awarded him $289 million, saying that Roundup contributed to his fatal cancer. More than 2,000 other individuals suffering from non-Hodgkin’s lymphoma have since filed suit.

Monsanto/Bayer denies any link between the product and terminal cancer and plans to appeal the ruling. Yet the evidence for a causal relationship between cancer and exposure to Roundup, glyphosate, other glyphosate-based herbicides and organophosphate pesticides is mounting.

So is public awareness.

Boblitt said he is aware of these trends, and since Cortez is known for its parks, his job requires him to minimize exposure to harmful agents while also adhering to state and county noxious- weed regulations. “We want to be responsible in what we do,” he said. “Public safety is paramount.”

The EPA does not consider glyphosate a human carcinogen, but is reviewing the research. Some of this research includes evidence that switching to an organic-only diet reduces herbicide levels in the body.

One study found that when school children in Seattle began eating an all-organic diet, their levels of herbicide residue dropped to non-detectable levels.

Minimizing exposure

But many farmers, municipal officials, and property owners say it isn’t feasible to control weed infestations completely without chemicals. In Mancos in particular, the town board and staff have struggled to deal with the concerns over the use of herbicides in the parks.

A group of people had stepped up to say they would pull weeds by hand, but over time the number of volunteers dwindled. Meanwhile, some people using the parks complained that their dogs were getting weed seeds such as cheatgrass in their fur and ears, and the county weed department had said the parks contained several noxious weed species.

So the dispute continues. However, on an individual basis, there are ways to minimize exposure:

  • Eat more organic foods, and
  • Stay away from areas that are known to have been treated with herbicides and/or pesticides.
  • Find out what plants are considered noxious, and how best to treat them. When possible, use a mode of weed control that does as little damage to humans and the environment as possible.
  • Keep in mind that there are local, state and national organizations devoted to informing the public about the health impacts of herbicide and pesticide use. Locally, town and city officials can also be of help.


USGS Pesticide National Synthesis Project

Colorado.gov Pesticide Division complaint form:

Types of herbicides and their impact

National Pesticide Information Center

Pesticide Action Network

EPA information on endocrine disruptors

From October 2018. Read similar stories about .