Pesticide sprayed via drone in Millcreek, Parley's canyons to kill invasive weed

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SALT LAKE CITY — The Division of Wildlife Resources recently sprayed pesticides in the foothills of Millcreek and Parley's canyons to try and kill myrtle spurge, a nonnative invasive species of weed whose sap can cause skin irritation, redness, swelling, and blisters in humans and kill habitats for wildlife.

The treatments, however, worried residents and one environmental advocacy group who said the chemicals are harmful, despite their Environmental Protection Agency approval.

The spray is a combination of Roundup (glyphosate) and Telar (chlosulfuron), along with a surfactant and a purple or blue dye. The dye was included so people and pets could know where it was sprayed before it dried.

The agency said the treatment was the most effective and EPA-approved solution to kill these potentially harmful weeds.

"The herbicides that we have been using, they've been approved by the Environmental Protection Agency for land managing agencies to use when dealing with invasive plants," Faith Heaton Jolley, a spokeswoman for the division, said. "And they have found there are no risks to human health when this type of treatment is used in accordance with its current label."

But the local environmental advocacy group Utah Physicians for Healthy Environment said the chemicals have known harmful impacts, like cancer.

"These chemicals are biologically toxic, not just to vegetation, but to mammals, to wildlife and to humans," Brian Moench, the group's president, said.

"No one would say that cigarettes are safe to smoke. Yet the FDA has approved the sale of cigarettes. The EPA has approved the sale of these pesticides. That doesn't mean that they're safe to use, and it doesn't mean they're safe to use in this kind of context from drones and in an area that's fairly heavily populated," Moench said.

Earlier this year, a Pennsylvania jury ruled that Roundup caused a man's cancer because of its key ingredient glyphosate and awarded him punitive damages.

Thousands have sued the makers of Roundup over similar claims. But in 2020, the EPA approved both the herbicides and determined there are no risks of concern to human health when used in accordance with its label.

Over the last several years, the Utah Division of Wildlife Resources has been pulling these weeds in Parley's and Millcreek canyons manually.

Suicide Rock is seen in Parley's Canyon in 2023 before the myrtle spurge was sprayed with treatment.
Suicide Rock is seen in Parley's Canyon in 2023 before the myrtle spurge was sprayed with treatment. (Photo: Utah Division of Wildlife Resources)

"Mechanical removal by hand has proven to be minimally effective with myrtle. With how widespread the infestation has become, mechanical removal is not feasible," Jolley said.

They started using a drone to spray along foothills and in areas that were hard to reach.

"It's a targeted treatment area, and we have specific guidance when we're using these," Jolley said. "We've used these according to the label so that we're making sure the mixture doesn't become airborne, and it's sticking to these plants and not going all across the landscape when we're using it."

The drone use, Jolley said, proved much more effective.

Suicide Rock is seen in Parley's Canyon in the spring of 2024 after the area was sprayed with treatment for myrtle spurge.
Suicide Rock is seen in Parley's Canyon in the spring of 2024 after the area was sprayed with treatment for myrtle spurge. (Photo: Utah Division of Wildlife Resources)

"Roundup kills the myrtle spurge and kind of the roots so they won't come back. And then telar helps prevent the seeds from germinating," Jolley said.

But Moench worries that the danger of the use of the chemicals won't be realized until years down the road.

"The idea that we just have to get rid of myrtle spurge at any cost, and it's worth spraying this kind of biologic toxic chemical throughout the community in order to achieve that, we think that's a terribly misplaced priority," he said.

The spraying started in March and will wrap up this month.

Areas sprayed are at Parley's Pointe, and Grandeur Peak Open Space in Parley's Canyon and in east and west Millcreek Canyon. People and pets are advised to avoid these areas if they see the blue-dyed leaves.

The Division of Wildlife Resources determines where and how to spray, but the project has the sign-off of several other agencies who are working with them, including the Salt Lake County Health Department.


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Lindsay Aerts
Lindsay is a reporter for KSL-TV who specializes in political news. She attended Utah State University and got a degree in Broadcast Journalism. She previously reported for KSL NewsRadio.


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