Gardeners And Farmers At Increased Risk Of Unintended Effects From Increased Herbicide Use

With temperatures heating up and spring showers moving in, this is a busy time of year for gardeners. But experts are warning gardeners and farmers to be more aware of the mulch and organic material they add to their soils.

Jim Rye loves to garden. A Monongalia County master gardener, he’s been doing it for close to 40 years, and extols its virtues not just for the fruits and flowers in yields, but also for its educational benefits. 

“I would like to see more schools, elementary schools especially, making room for school gardening as a means to teach science, math, English, language arts,” Rye said.

It even lays a foundation, he said, for a future career in biology or environmentalism. Which is why a few years ago, Rye was devastated to see that something was wrong with the tomatillos he was helping a Morgantown elementary school grow.

“We noticed that the leaves were curling and some of the leaves looked like cups,” he said. “I’m pretty familiar with tomato leaves.Tomatillos are a relative of tomatoes, soiI just didn’t look right to me.”

Rye is fairly certain the contamination came from grass clippings that were donated to the garden by a school family and used as mulch. He believes the clippings had been treated with an herbicide to suppress weeds, something he had specifically warned against, and suspects the herbicide then seeped into the soil to ultimately damage the tomatillos.

Mahfuz Rahman, a plant pathology extension specialist and the director of the West Virginia University Plant Diagnostic Clinic, said the damage Rye describes is typical of herbicide contamination. 

“People are using those to control weeds in their fields, in their farms, in their backyard, and also there are herbicides used for controlling invasives,” he said. “It has a huge impact on agriculture. We need it, but at the same time, we need to be very cautious in how we use it.”

Rahman said herbicides can linger on grass clippings or hay from lawns and fields for years. Once contaminated material is applied to a plot, the soil becomes contaminated too. 

“If they see something, some plants are affected, or showing symptoms of herbicide contamination, they can definitely, not use the compost in the same year,” Rahman said. “But if they can keep that compost for another couple of years, most of the active ingredients can be degraded, so after that period of time, it can be safe for them to use.”

Rahman said herbicide contamination and damage has been an issue as long as the treatments have existed, but they do seem to be on the rise in recent years. Since 2019, state extension programs across the country, from Washington to North Carolina, have started publishing warnings to gardeners and farmers to be careful not only when using herbicides but also when using materials that have been treated with herbicides. Rahman published his own “Ag Alert” for West Virginians in April of 2023.

He theorized the increase in contamination is due, in large part, to longer growing seasons causing more weeds to grow.

Some of the plants used to grow in the south, and some of the disease-causing organisms we used to see in the southeast, now we are seeing it here because of the temperature change,” Rahman said. “So some of the invasives are getting to the north and also their growing season is longer.”

Easier access to these chemicals is also driving use and contamination.

”These products are getting more and more available in the local stores,” Rahman said. “If you don’t want to go to the store, just go online and place an order. It will be on your doorstep in two, three days.” 

On top of that last point, Rahman said the issue boils down to misuse. He said oftentimes, the homeowners and agricultural workers that contact him do not fully understand the products they use, or accidentally cross-contaminate by using the same sprayers for herbicide and insecticide.

“The toxicity of these products to humans is very low,” Rahman said. “But the most important thing is when you are buying these products, you have to follow the label. On the label it says how to use it. After using how many days you should not harvest or you should not enter into that treated area.” 

Rakesh Chandran, professor and extension specialist of weed science at WVU, agreed with Rahman that it is the herbicide user’s responsibility to use the products safely and understand the full impact of what they’re doing.

“If a herbicide is used according to the label, there are minimal risks associated with it,” he said. “For example, there are a few herbicides that are labeled or they’re used in pastures or hay fields, whereby it specifically states on the label that ‘Do not remove the hay or any clippings from the field where it was applied outside the farm.’ In other words, all the hay should stay within the farm where it was treated.”

The damage to Rye’s tomatillos could have been avoided if someone had just read the label. 

Chandran said it can be difficult to pinpoint what he calls “non-target” damage caused by herbicides. Chandran and Rahman both suggest conducting what is called a bio-assay to confirm contamination. 

“If it’s a straw mulch, you take some of that mulch and mix it with good potting mixture, good meaning uncontaminated potting mixture,” Chandran said. “Then you sow some sensitive seeds, say cucumber or peas or tomatoes. Once it germinates, if it shows any signs of distorted growth, then that’s an indication that herbicide residue is present. To confirm that, what one would need to do is to have a control or have a treatment which was not contaminated.”

On a small scrub field on WVU’s Animal Science farm in Morgantown, weeds have been allowed to grow freely. Here, Chandran has treated two patches. One lacks the thistles and tall weeds of the surrounding field, but still has clovers and some other plants growing. The other is yellowed and dry, with almost no life. 

“This is typically the kind of injury that you would see in a garden,” Chandran said. “For example, if it’s a pepper plant or a tomato plant, it will show exactly this type of injury from herbicide residues. Whereas the new herbicide that we are developing, you don’t see those types of injuries.”

Chandran is developing the next generation of herbicides, one he hopes will be even more focused on controlling unwanted plants and leave beneficials like clover, and the unsuspecting tomatillo, alone. 

But even once the new stuff hits the markets in a few years, it will still be worthwhile to read the label.