Unintended Consequences of Lawn Herbicides

Is Your Weed Killer Poisoning Your Trees and Gardens?

Unintended Consequences of Lawn Herbicides

By Aleisha DjuricicWisconsin, Zone 5B

Lawn herbicides don’t just kill weeds. All broadleaf plants can be damaged.

My modest urban homestead is located a short distance from the western shore of Lake Michigan. We’re fortunate to be surrounded by lovely homes and estates, which line the lakeshore. Many of these homeowners employ their own personal lawn and landscaping services.

On many summer mornings, you can hear the roar of lawnmowers and leaf blowers used by landscapers laboring on neighboring properties. The workers leave behind perfectly trimmed and edged lawns, along with pesticide warning signs. These tiny white signs dot many of the lawns in my neighborhood.

[optin-monster-shortcode id=”k7fvz8wek0u9ohtoglrz”]

When we purchased our house, the lawn had almost no weeds, and it was a lush green carpet that had been well cared for and regularly watered. Not only did it take enormous amounts of water to maintain, but it also needed bags of chemical fertilizers and lawn herbicides to keep it lush, green and weed-free. It wasn’t long before we decided the cost, effort, and risk involved in keeping the lawn maintained was not worth it. Of course, I was not always sure how my neighbors felt about our less than perfect lawn. That is until I happened to be chatting with a neighbor about how lovely his new landscaping was.

Bill, my neighbor, told me he hadn’t planned on digging out his entire front yard and replacing the landscaping this year, but he had to do it. Puzzled about this, I asked him why he “had to” complete the landscaping this year. That’s when I found out the lawn-care company he hired to regularly weed and feed his lawn had used a lawn herbicide called “Imprelis®.” The product, which is made by DuPont, had been applied to his lawn all spring and summer. Bill told me it made his lawn look beautiful, and killed off all the broadleaf weeds—but it also killed all his evergreens. In fact, Bill not only had to replace the evergreens, but he also had to pull out the sod and every plant in his yard, plus remove the topsoil. All the plant materials and soil had to be placed in a landfill because of the risk that these materials were toxic to other plants. Composting the plant materials would not break down the chemicals enough to make them safe to use either.

Shocked, I expressed my concern to Bill and asked him whether any of the neighbors who used the same lawn care service were affected as well. He pointed to the house across the street from his and told me all of the evergreens on his neighbor’s property had died—but the damage had been temporarily camouflaged by applying a green vegetable dye over all the evergreens. I joked to Bill that this reminded me of “painting the roses red” from the story Alice in Wonderland. Then I shared with him that my family had intentionally made the choice to not use these types of chemicals on our lawn because of the risks. While I wasn’t always proud of how our lawn looked compared to all our neighbors, I also wasn’t afraid to let my kids play on the grass. This also allowed us to safely incorporate blueberries and other edibles into our landscaping. As Bill considered these things, I handed him an organic squash from my garden. Before we parted ways, I was able to share a little more of my philosophy on lawns, and my plans to gradually replace additional sections of our lawn with more plants that provide food or benefit wildlife.

While packing up my garden tools that evening, I mentally counted the number of homes in my neighborhood which employed the same lawn care company Bill had hired. Sadly, at least half the homes had hired them. Even more, I knew at least two-thirds of my neighbors employed lawn-care companies which regularly used lawn herbicides and pesticides. I decided to conduct some research on Imprelis® and other lawn herbicides to better understand the risks and issues involved.

Lawn herbicide use in one yard can negatively affect the whole neighborhood. Photo by Paolo Neo

Lawn Herbicides: The Facts

A quick Internet search on “Imprelis” immediately directed me to a website hosted by DuPont, the company which makes and sells the lawn herbicides. Imprelis-facts.com provided easy-to-understand information about the problems the product has caused, as well as how to remediate areas where the product was used. The good news is the product was taken off the market in August 2011, and the EPA has ordered the company to cease the sale, distribution, and use of the lawn herbicides. Additionally, DuPont has started a product return and refund program. According to the site Imprelis-facts.com, the company has “has initiated a claims resolution process to compensate and in some cases assist lawn care operators and property owners in the replacement of trees that may have been damaged through the use of Imprelis.”

DuPont provides detailed information about how to remediate locations where Imprelis has been used. The company “recommends disposal of tree and excavated soil materials in solid waste landfills.” The guidelines also state that “The Imprelis label prohibits the use of clippings for mulch or compost. Under no circumstances should tree material be used for mulch or compost.”

Lawn Herbicides: The Issue

According to DuPont, they have received reports of problems due to Imprelis use “primarily concentrated in a geographic band that includes Minnesota, Michigan, Indiana, Ohio, Pennsylvania, New Jersey and Wisconsin.” Imprelis, also known as aminocyclopyrachlor, was only in use for about a year, but other persistent lawn herbicides remain on the market.

Aminocyclopyrachlor, aminopyralid, clopyralid, fluroxypyr, and picloram are in a class of herbicides known as pyridine carboxylic acids. They are found in a variety of lawn herbicide products used in residential, commercial and agricultural applications where the reduction of broadleaf plants is desired. These chemicals remain in the soil for quite some time and are easily absorbed by grass plants—with residues persisting even in composted manure and plant materials. Animals that graze on pasture treated with lawn herbicides in this class excrete the chemical in their urine and manure.

The Environmental Protection Agency (EPA) states that these chemicals are safe and appear to cause little harm to humans and animals. However, reading the labels for these products is more frightening than any ghost story. One product label warned that getting the product in the eyes can cause irreversible eye damage. In the case of Imprelis, the nine-page product label warns the user to “not use grass clippings from treated areas for mulching or compost, or allow for collection to composting facilities.” The product label for Forefront, an herbicide containing aminopyralid, cautions users not to use “animal waste from animals fed on grass treated with Forefront” on sensitive crops such as peas, beets or other non-grass plants. Additionally, users are told to wait at least one year after the last application before planting sensitive crops in treated fields.

Both DuPont and Dow Agrosciences provide general guidelines about how much time it takes for the chemicals to dissipate from the soil. However, the rate of dissipation is dependent on multiple factors including temperature, soil moisture and the amount of organic material in the soil. In the case of Clopyralid, “Crop injury and yield loss may occur up to four years after application.” (EPA Registration for Clopyralid #34704-885, August 24, 2005.)

About 10 years ago, the composting facility for Washington State University experienced problems from herbicide contaminated manure and bedding. The University discovered that composts contaminated with these lawn herbicides—in amounts as small as 10 ppb (part per billion) — negatively affected susceptible vegetable and flower plants such as:

• Peas, beans, and other legumes

• Lettuces, endive, and sunflowers

• Tomatoes, peppers, potatoes and eggplants

• Carrots and celery

When sensitive plants are exposed to these lawn herbicides, they may develop cupped or fern-like leaves and twisted stems, and they do not produce well.


Lawn Herbicides: What’s In a Name?

Many sources recommend that you ask your supplier of straw, hay, mulch, manure or compost whether these chemicals have been used by them or on their land. However, I believe this is problematic itself. First, if you are able to speak directly to the supplier, asking about aminocyclopyrachlor, picloram, clopyralid, and aminopyralid is probably not enough. You’ll need to ask about specific trade names of the lawn herbicides, which include:

• Picloram: sold as Tordon, Access, Surmount, Grazon, and Pathway.

• Clopyralid: sold as Curtail, Confront, Clopyr AG, Lontrel, Stinger, Millennium Ultra, Millenium Ultra Plus, Reclaim, Redeem, Transline.

• Aminopyralid: sold as Milestone, Forefront, Pharaoh, Banish.

• Aminocyclopyrachlor: sold as Imprelis (prior to the EPA’s stop sale order in August 2011).

The chemicals are also listed on product labels under a variety of different names. For example, information found on the National Pesticide Information Center Web site showed the herbicide aminopyralid may be labeled under the following names:

NXDE-750 TIPA salt

NTriisopropanolamine salt of aminopyralid

N2-Pyridinecarboxylic acid, 4-amino-3,6-dichloro-, compd. with 1,1′,1″ -nitrilotr is[2-propanol] (1:1)

NXDE-750 Triisopropanolamine salt


N2-Pyridinecarboxylic acid, 4-amino-3,6-dichloro-

NCAS Reg. No. 150114-71-9


N4-Amino-3,6-dichloropyridine-2-carboxylic acid

Even if you asked a landscaping company or mulch supplier whether they use any herbicides containing aminopyralid, there is a strong possibility the supplier or landscaper may not know. Especially if the label does not clearly show that “XDE-750” is another name for aminopyralid.

Who Uses These Chemicals and Where?

These lawn herbicides are used by farmers and ranchers to control broadleaf weeds in pasture lands for grazing animals, and in crop fields where grass crops such as wheat, corn, or barley are grown. They are also used by landscaping companies and licensed handlers of these chemicals, such as highway departments or utility companies, in order to manage broadleaf weeds in golf courses, lawns, cemeteries, athletic fields, and along roadways or around transmission lines. There is even a chance nurseries or sod farms have applied these products—increasing the risk that homeowners could unknowingly bring the product onto their property.


Contamination can occur when a property owner uses contaminated materials such as:

• Contaminated mulch—hay, straw, grass clippings or wood chips.

• Contaminated manure and bedding from livestock which have been fed crops treated with these herbicides, or which have grazed in treated pastures.

Composting ingredients made from contaminated hay, grass clippings, animal bedding, and manure.

• Contaminated plant materials from a nursery or sod farm.

Contamination can also occur due to run-off or over-spray from an adjacent property where these chemicals are applied. Risks for cross-contamination can occur in dry, windy areas when treated soil becomes wind-blown into neighboring properties. Consider the properties adjacent to your own. Do you live next to a golf course, park, farm, or do your neighbors use a lawn care service? Is your property adjacent to power transmission lines or next to a roadway where herbicide spraying is conducted?

Taking a pro-active approach towards this issue is the most effective way to ensure your property does not become adversely affected by herbicide use.

• Do not accept compost, mulch or manure if you cannot verify its safety. Be suspicious of straw, mulch or compost sold specifically for use only on grassy areas.

• Test soil, mulch or compost before use. (See Testing for the Presence of Herbicides)

• Ramp-up your own composting operation so you are less reliant on external sources.

• Make your own mulch—use safe grass clipping or shredded leaves from your property.

• Sign-up for your state’s pesticide registry so you know more about the products lawn care companies use on neighboring properties. To find out if your state has a pesticide registry, contact your local EPA office or conduct a search online.

Testing for the Presence of Lawn Herbicides

Lab testing for lawn herbicides is available, but it is possible to conduct a simple soil test (also called a bioassay) to determine if herbicides are present.

To conduct the test, gather the following materials:

• 1 gallon of the soil, manure, compost or mulch material you want to test

• 2 gallons of commercial potting soil

• 6 small pots (sized about 4″)

• 6 pot saucers

• Pea, bean or other legume seeds (18 seeds)


Prepare the control pots by filling them with commercial potting soil, and mark these pots as the control pots. Place a pot saucer under each pot. Next, plant three seeds in each control pot, then water.

Prepare the test pots by mixing one part of the test material with one part of the commercial potting soil. Fill the test pots and clearly mark them. If you are testing hay or mulch, just use the materials to provide two inches of top-dressing in pots filled with commercial potting soil. Be sure to place a pot saucer under each pot. Next, plant the test pots with three seeds per pot, then water. Important: be sure to use pot saucers to reduce the risk of cross-contamination resulting from water leaching from one pot to another. Continue to water the pots as needed, letting them grow for about three-to-four weeks — until the plants have at least three sets of leaves.

Reviewing Test Results

After plants have obtained three sets of true leaves, compare the plants in both groups. Look for signs of abnormal growth in test pots, such as twisted stems, cupped leaves, or fern-like growth on new shoots. If the plants in the test pots appear abnormal in comparison to plants in the control pots, there is a strong possibility of contamination. If all the plants grow normally, it is fairly safe to assume the material is safe.

A similar test can be conducted on a field scale by planting legumes randomly across the suspected area.

Many university extension offices provide detailed instructions and information about soil testing and field bioassays.

Dealing with Lawn Herbicide Contamination

If contaminated materials have already been applied to your property, sow a non-sensitive cover crop and let it grow for a year or two to help the lawn herbicides break down. Alternatively, smaller locations can be remediated by removing all existing plant materials and replacing the first few inches of topsoil with clean material mixed with activated charcoal. Be sure to do a soil test before planting any sensitive crops. Harmful incidents resulting from lawn herbicide use should be reported to the state environmental agency and to the National Pesticide Information Center.

Have you dealt with damage from lawn herbicides? Tell us your stories!


Online list of state environmental agencies: www.epa.gov/epahome/state.htm.

National Pesticide Information Center Web site: http://npic.orst.edu/reportprob.html; E-mail: npic@ace.orst.edu. Phone: 1-800-858-7378. Mailing address: National Pesticide Information Center, Oregon State University, 333 Weniger Hall, Corvalis, OR 97331-6502.

Originally published in Countryside March/April 2012 and regularly vetted for accuracy.

Leave a Reply

Your email address will not be published. Required fields are marked *