Finding the right prescription to battle weeds

Aug 15, 2017

Paul Schreiner of EcoRx sprays weeds near the Rim Trail in Snowmass Village.
Credit Elizabeth Stewart-Severy / Aspen Public Radio

Across the west, noxious weeds damage ecosystems, and local governments are tasked with keeping them at bay. But the solution — chemical herbicides — doesn’t always sit well with residents.


Paul Schreiner spends his days hunting noxious weeds, like hounds tongue. When he spots one, he kills it. Though he has a different take on his work.


“I’m kind of like the doctor that’s writing the prescription,” Schreiner said. “I go out there, my patient is this hillside.”


On one stretch of roadside in Snowmass Village, Schreiner can spot a host of maladies. He points out plumeless thistle, Canada thistle, poison hemlock, oxide daisy, mayweed chamomile, hounds tongue.


They are all noxious weeds — non-native, invasive plants that pose a threat to the ecosystem.  Schreiner is the owner of Eco Rx. He’s been hired by several local agencies, including the Town of Snowmass Village and Pitkin County Open Space and Trails, to manage these weeds.


Schreiner studied both botany and chemistry. He said an area like this, which is about half noxious weeds, is a serious problem.

“Really it’s a starvation zone for our food chain," he said.


Noxious weeds are toxic or inedible to native insects. When the bugs can’t find enough food, the ripple effects move up through the food web.


“Once we start losing small rodents and birds, then we start losing raptors and small predators, and then, of course, there's a direct effect on our herbivores," Schreiner said.


Schreiner’s prescription to eradicate the weeds is chemical. He walks through the tall grasses with a pressurized backpack full of liquid herbicide. He admits that he’s pretty heavy-handed in his treatment, continuing with the doctor analogy as he pumps and sprays herbicide on a hillside in Snowmass.


“You're going to cause some damage to native cells,” he said. “But once you’re cured of the cancer, you’re expecting that damage will repair itself.”


His take is that, post-herbicide, the weeds die off, but the ecosystem heals and the native plants and grasses reclaim their territory.


But this chemo-therapy approach doesn’t sit well with some residents.


“We spray chemicals on things and we just walk by and say, ‘Ok, well it’s the lesser evil,’” said Kendall Cafritz, who lives in Snowmass Village.


Some residents in Snowmass Village have asked that town officials exempt their neighborhoods from chemical herbicide.
Credit Elizabeth Stewart-Severy / Aspen Public Radio

Herbicides aren’t the only means for controlling weeds – but they are the preferred method for large stretches of roadside. The chemical fix is faster and more efficient than pulling the weeds by hand, for example, and cheaper than a creative fix like using goats. But Cafritz thinks using manpower would be worth it.

“Something in my gut says we can do a lot better, and that we’ve taken an easier route, and it’s just us being a little bit lazy,” she said.


Plus, she’s concerned about the health impacts of pesticides. By definition, herbicides are toxic to some plants. These types of chemicals are tested by the EPA, but some have criticized the process for not being cautious enough, and Cafritz has a host of concerns, including irritation to the eyes and skin and respiratory symptoms.

But Ben Carlsen, city forester in Aspen, said local governments use the least harmful herbicides, ones that are not toxic to mammals.


Residents who feel some of those adverse effects of herbicides can join the state of Colorado’s pesticide sensitive list, and some neighborhoods in Snowmass Village have posted signs saying “Do not spray, pesticide free zone.” Still, land managers in Colorado are required by law to control noxious weeds.


Carlsen said working to protect the ecosystem from invasive species is complex – and there’s not one magic bullet.


"You need to be able to mechanically pull weeds, you need to be able to spray weeds, you need to be able to set biological controls like insects that will eat the weeds," he said.


And some weeds can’t be controlled by hand.

"If you pull a perennial weed, the roots just sprout 10 more plants in the same spot,” Carlsen said. “So the only effective way to treat a perennial weed is to spray it.”


Schreiner agreed, looking at a hillside sprouting weeds in Snowmass Village.


“I could treat this one-acre in 45 minutes,” he said. “It would take a hand crew of three probably a day and a half, two days.”


Each plant can have thousands of seeds, which are viable in the soil for sometimes over a decade. Seeds are dispersed by cars, winds, even on clothing, and they take root easily in any soil that has been disturbed by humans. Think construction sites and new trails.

“Man is an excellent vector,” Schreiner said. “We're the ones that cause this."


And the ones tasked with undoing the damage.