Summit County has a secret weapon in fight against noxious weeds: bugs
Myrtle spurge, yellow starthistle, dyer’s woad, musk thistle — ingredients for a potion these are not.
They’re invasive, noxious weeds, and along with dozens of others are threatening native plant species around Summit County, a problem that can have economic as well as ecological impacts.
But in recent years, the county has enlisted an unusual ally in the fight for weed control: bugs.
The county’s Weed Superintendent Dave Bingham said his office uses a half-dozen techniques to curb the spread of invasive weeds, from education and outreach to herbicides and yanking them out by hand.
Bugs, under the “biocontrols” umbrella, are “one of the tools in the toolbag,” Bingham said. Biocontrols use invasive plants’ natural enemies like insects and fungi to slow, contain and control the invaders’ growth. He and the county rely on “Utah’s Bug Girl,” Amber Mendenhall, to help them in this effort. Bingham lauded her expertise and experience in setting up biocontrol management strategies.
“Amber’s checked into all of this, so I can go to work,” he said.
On a recent summer morning, Mendenhall and Bingham headed to a sort of insect farm on private land in the Weber Canyon. They were checking on a colony of stem-mining weevils they’d set up in a meadow near the river, with hills climbing steadily in the background and a clear blue sky overhead. The were breeding the bugs to combat a Dalmatian toadflax invasion on the site, and if the population grew large enough, they pllanned to move some of the bugs to other areas around the county and state.
Bingham had maintained the structure over the winter, tromping in his snowshoes to clear snow that threatened to crush it. Mendenhall said that’s one of the things that makes Summit County great to work with — the dedication of its staff, as well as their diligence in mapping patches of weeds and what they’ve done to mitigate them.
She said Summit County is a regional leader in adopting biocontrol techniques, along with Cache County.
“Summit County has the most well-researched plots in the state,” Mendenhall said, and with the most diversity of biocontrols.
Vegetation and treatment maps can become outdated in less than a year, she said, and the newer the data is, the easier it is for her to do her job. When Bingham uploads his teams’ field reports charting locations of weed patches and the techniques they’ve used on them, Mendenhall is able to create a biocontrol plan with a better chance of succeeding.
The insect-rearing cage is a mesh rectangle standing less than six feet tall. It increases the insects’ reproduction rate exponentially, allowing a population to establish itself within a year where it would otherwise take three to five years and more tending.
Dalmation toadflax is a deceptively pretty green plant with yellow flowers that, like other invasive species, chokes out native grasses.
Invasive plants can lower the number of animals an acre of land can sustain, kill food sources for wild animals and upend ecosystems, diminishing the value of crops. Areas that benefit from ecotourism have even more on the line, Mendenhall said.
Montana, for example, established a $1 million fund to fight noxious weeds after it was demonstrated that they crowded out elks’ natural food source and the animals’ population declined, reducing the number of hunters, Mendenhall said.
Inside the structure, the weevils had already decimated the toadflax. They’re known as “stem-mining” because the parents lay their eggs inside the stems and the larvae consume the inside of the plant.
“The children destroy stuff, the parents have sex,” Mendenhall said. “These plants are dead now, they just don’t know it.”
The parents also chew “windows” into the leaves, diminishing the toadflax’s ability to gather energy from the sun.
Pointing to a dessicated, gray stem, Mendenhall noted a dozen holes that indicate the bugs’ entrances and exits, and the two-inch seam the bugs had caused that she said spelled the plants’ demise.
The weevils are a “rockstar” biocontrol, Mendenhall said, unusually successful at killing their target. Mendenhall explained that biocontrol techniques generally kill plants by weakening them and paving the way for a secondary infection or infestation to take them out.
That’s one way invasive species attack native ones, too. Garlic mustard, for example, increases the stress on conifer species, disrupts the fungal network and weakens the trees to the point they can’t defend themselves against fire or attackers like beetles.
Mendenhall hopes for a 70 percent reduction of the toadflax population over 10 years, but noted that insects “don’t eat themselves out of house and home.”
She said biological controls have only gotten better in recent years and pointed to “better science” as the reason why.
“Ten or 15 years ago, we’d just shotgun it,” Mendenhall said, throwing biocontrols into the field because they’re low-cost and low-risk. Now she’s more reliant on data.
She and colleagues from Western states have quarterly conference calls that focus on what works and what doesn’t. They share experiences and sometimes raw materials.
Biological controls are less expensive and harmful than other techniques, but it wasn’t always so. Mendenhall told of some experiments in the 1960s when scientists released organisms that they then had to corral because of the damage they were doing to other species.
Since then, an international effort has led stiff regulation involving decade-long quarantines and oversight boards.
Now, when the weevils are released, Mendenhall and Bingham can be confident they won’t turn up munching on something that threatens the food supply.
Summit County spends about $10,000 a year on bugs, a number that Bingham said is well worth it.It has also received about $400,000 in state and federal grants to fight weeds for 2019, according to a presentation at a recent County Council meeting.
It’s up to private landowners to control the weeds on their property, but they have help from the county’s weed department. Bingham oversees a program that loans out different kinds of sprayers, from backpacks to tractor-mounted systems, all for free. He will also help in formulating a treatment plan.
He’ll recommend anything from Round-Up to weevils, though biocontrols are generally best on large parcels of land. He also sells herbicides to residents at the cost he paid for them. The county sold about $80,000 worth in 2018.
It’s easier to deal with noxious weeds than people think, Bingham said, often requiring a few hours a year and $25 or so for supplies.
At a recent County Council meeting, Bingham asked for more funding to add a second full-time enforcement officer. That would augment a team of six employees who also go out into the field and identify problem areas.
But the insect allies don’t need a salary, and at $1 a pop, are quite a deal. They’ll range and find the target plants in areas humans can’t or won’t go, and they hardly take a day off.
“By money, biocontrol is very small,” Bingham said, “but it does the most work.”
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