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Multiple tactics target invasive weedMultiple tactics target invasive weed

In Wyoming, ranchers and farmers use herbicides and a weed-eating bug to get the job done.

August 16, 2019

4 Min Read
Dalmatian toadflex
BIG TROUBLE: Dalmatian toadflax started as an ornamental plant imported to the United States and is now a troublesome weed, but a coordinated effort to control it is making a difference for Wyoming ranchers.George Beck, James Sebastian, Bugwood.org

Recently, the University of Wyoming issued a feature release based on a recent Dalmatian toadflax field day. What follows is that report:

Cheyenne-area rancher Nina Haas walked slowly in the range grass, which was lush from summer rain, looking down at Dalmatian toadflax plants. Then she stopped.

Something had grabbed her attention, and she went down to one knee for a closer look. “There,” she pointed to one of the leaves on a plant. A round hole had been bored through, one telltale indication of a Dalmatian toadflax stem boring weevil (Mecinus janthiniformis) at work.

UW Extension invasive plant specialist Dan Tekiela. the USDA Animal and Plant Health Inspection Service and the Laramie County Conservation District were also involved with the Dalmatian toadflax field day.

As if coming out from behind a curtain on cue, a little black weevil with legs churning treaded from under a leaf and continued upward, oblivious to humans. It was going about fulfilling its USDA-mandated biocontrol job of munching, and ultimately injuring, the invasive plants on the range at the High Plains Grasslands Research Station just west of Cheyenne.

Those attending the Dalmatian toadflax field day recently would later wave sweep nets and sweep the insects off plants. USDA workers used respirators to suck the valuable bugs into small glass jars for attendees to take them home and release them.

The beetles were only 10 feet away from herbicide trials by Dan Tekiela, UW Extension invasive weed specialist.

The side-by-side examples were exactly what Tekiela wanted attendees to see — multiple approaches to Dalmatian toadflax control.

Working in tandem

“Herbicides aren’t the only option,” Tekiela said. “An integrated approach is appropriate, but understand not all management approaches are applicable to all situations. That’s really important.”

Dalmatian toadflax is native to the Mediterranean region (including the Dalmatian Coast of the former Yugoslavia) and was intentionally introduced into the U.S. as an ornamental plant in the late 1890s or early 1900s. Tekiela said horticultural reports from 100 years ago state the plant seemed to survive well, but wasn’t very pretty.

“That’s such a perfect statement of an invasive,” Tekiela said. “Here we are, 100 years later, and it’s one of the more problematic species in the Western U.S.”

The weed hasn’t yet blown to proportions like Canada thistle. Dig a teaspoon of soil anywhere in Wyoming, and Canada thistle seeds are there, Tekiela said. He believes there is an opportunity to slow Dalmatian toadflax’s spread because the plant hasn’t advanced that far.

“You can save a lot of money if you don’t let it get to that point,” he said. “With the increasing density of Dalmatian toadflax is the decreasing density of the other desirable plants you want. Getting those back is hard. Killing a plant is easy. It’s getting what you want there that is hard.”

There isn’t one silver bullet, and thinking about multiple management strategies on your property may lead to the best result, he said. Biocontrol can work in some scenarios but is not feasible in others, Tekiela said. Herbicides may be good options in others.

Justin Lauderbach and son Devon Lauderbach of Cheyenne looked for Dalmatian toadflax boring weevils. Those attending the field day could catch and take home weevils.

The herbicide trials showed more than what would wreak havoc on the invasive weed. Tekiela is also interested in knowing and showing how much the surrounding native plant community can benefit from management.

“I can go out and kill plants, make a moonscape out of something — but that’s not what our goal ever is,” he said. “[That goal is] get rid of one plant and keep everything else.”

Beating a challenging weed

Dalmatian toadflax has been a focus for Tekiela because it is challenging to manage. He said its waxy coating makes herbicide control difficult. Leaves will even squeak if rubbed together.

“That wax is almost like a protective coating, a coat of armor” to herbicides, he said. But not to the beetles.

Adult females lay eggs in the stems in the spring, and the larvae hatch and begin feeding on the inside of a stem. The beetles do not kill a plant but greatly reduce its vigor, according to information from the Colorado Department of Agriculture. After many years, sites have been known to collapse.

Bruce Shambaugh, Wyoming USDA Animal and Plant Health Inspection Service director, explained to attendees the process the agency uses for control of Dalmatian toadflax boring weevils. The beetles may have been a bit of a novelty for attendees: Many probably have applied herbicides, but not as many have netted beetles.

The participants could take them home if they provided information about how many beetles were released and where. Tekiela said tracking the beetles will enable better management decisions based on where they have been successful.

“The fact you are collecting a living organism that theoretically will be good for you if everything goes well is a neat concept,” he said. “Those weevils are not inexpensive, and to go out with an expert in the field like Bruce Shambaugh and collect weevils and take them home is incredible — not only for them [field day attendees], but it’s a neat opportunity for us in the weed management world.”

Source: University of Wyoming. The source is solely responsible for the information provided and is wholly owned by the source. Informa Business Media and all its subsidiaries are not responsible for any of the content contained in this information asset.



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