Tamarisk beetle follow the shrubs along rivers

By Sun Advocate

(This is the second in a three part series on tamarisk, an invasive species of tree which dominates the Colorado River and its tributaries banks. This week’s story picks up just a few years ago, when the tamarisk beetle was introduced to southeastern Utah. The beetle provides natural control for the trees in their native, Asian habitat—control which was lacking here).
Tamarisk eradication has been a priority for a number of public land agencies and large private land owners for years. The invasive trees take over ecosystems, increase soil salinity, channelize riverbeds, and create a fire hazard.
The trouble is, tamarisk is a pernicious weed. Each flower produces thousands of airborne seeds, and the steady upstream breeze along the Colorado River corridor insures that the plants will propagate themselves. Herbicide treatments and mechanical removal can clear an area, but tamarisks and other weeks soon move back in.
Grand County weed supervisor Tim Higgs said he did have some success with mechanical removal. However, that’s within the limited scope of his operations—the county doesn’t own much property. He concedes that one of those successes was quickly obscured by other weeds.
“Where we used it at Lion’s Park (just south of the Colorado River bridge north of Moab) people kept telling me it didn’t work, but there was probably 85, 90 percent kill of the tamarisk, you just couldn’t see it,” Higgs said.
Physically battling weeds, as any gardener knows, is a huge challenge. Conversely, poisoning weeds is expensive and hazardous. However, as any organic gardener knows, there is usually a natural counter to invaders.Turning to natural predators is called bio-control.
In the case of the tamarisk, its natural enemy is a small beetle, simply called the tamarisk beetle. In Asia, the tamarisk’s natural habitat, the beetle flourishes along with the plant. The small, striped insect feeds on the tamarisk’s foliage, limiting its growth, even killing some plants.
There had been limited releases of the beetle in Utah and Colorado, but with limited success. Then, in 2004, working with Utah State University and the Bureau of Land Management, Higgs helped release the first beetles in Grand County.
“In other areas they were trying to cover a large area, but with small amounts of beetles in each area,” Higgs said. “We were trying to get just a few areas with a large amount of beetles, and our area took off when the rest of the state really didn’t. Last year they started doing it the way we did, and they’re starting to see the effect.”
That effect of the bio-control has been dramatic. After the first year, the insects appeared to be doing their job, turning green tamarisks brown in a limited area around the releases. But by 2006, the beetles were moving rapidly up and downstream, giving new meaning to the term “brownout.”
“This year we’re probably going to see a total brownout along the river from around Cisco or a little north of the Cisco boat dock,” Higgs said. “It’s probably going to be a total brownout all the way down to Cataract Canyon. They’re going into the canyons in the Book Cliffs, where they’re browning out stuff up there as well.”
To say that the beetles have been prolific hardly covers it.
“I have no idea how to estimate how many are out there now,” Higgs said. “Out of all the releases, we probably had a couple hundred thousand. You’re probably talking hundreds of millions. In the wild, one female can produce 200 eggs, and you get two or three life cycles a year. If you bring in several thousand, and they do that—well, I’d have to play with the numbers.”
There is a long list of groups interested in the beetle’s success, and most of them are members of the Southeast Utah Tamarisk Partnership. The partnership includes most every state and federal land agency in Utah, as well as non-profit advocacy groups, conservancy groups, businesses, and land owners.
“It’s been an incredibly collaborative arrangement,” Grand Canyon Trust executive assistant Eleanor Bliss said. “The Nature Conservancy and the Grand Canyon Trust put forth some money so that we could get the management plan done. It was really important that we have a strategic plan so that we could actually apply for federal money. And there was a carrot out there in the form of federal legislation that was going to put some big money toward restoration work with tamarisk and Russian olive. So we got organized with the hopes of being able to apply as a group for some federal grants.”
With the 100-page strategic plan in place to guide the partnership, members have some direction to try to keep up with the voracious beetles. One of the most active members of the group has been the Bureau of Land Management, which manages large stretches of the Colorado River corridor, where the tamarisk invasion is worst.
“The beetle has really forced our hand because it’s been so effective and so widespread in its effect,” BLM fuels program manager Brian Keating said. “It has also elevated, at least in the short term, the fire hazard from the tamarisk.”
That presents a major issue in the river corridor.
“Last year we went to the extreme of actually closing some of the campgrounds along the river, because we really felt that there could be potentially a loss of life if there was a fire,” Keating said. “Some of these campgrounds, like Negro Bill, are one way in, one way out. The fire could close you off, and then you’re trapped.”
So Keating has overseen 250 acres of tamarisk treatment over the past winter to follow up on the bio-control. On 35 different units, crews have removed dying tamarisks to eliminate danger to the public, firefighters, infrastructure, and the remaining native vegetations.
“We don’t want to lose what’s already out there,” Keating said. “We’ve got fuel breaks out there where we could make a stand and stop the fire so we don’t lose the entire river corridor, so we don’t lose the stands of cottonwoods or pose a hazard to our recreational users.”
To avoid campground closures, some of the facilities were stripped of fuel.
“This winter we treated a lot of those campgrounds, and some of them that were 100 percent tamarisk cover are now clear cut,” Keating said. “The idea was that we could deal with the tamarisk and the beetle and the increased fire risk by closing these campgrounds, which isn’t a desirable outcome for either the BLM or our visitors, and we’d have to do that year after year. Or we could go in and remove the fire risk and follow up with an aggressive revegetation program.”
There have been some anxious moments for those taking on the tamarisks, even with the beetle’s success. This past spring was colder than normal, and some of the tamarisks began greening up before the beetles started to hatch.
“We were sort of speculating whether we were going to see brownout again, whether it was going to take some time to come back, how this was going to work,” Bliss said of speculation early in the summer. “Having it brown out in a week or 10 days made me realize that yes, they’re coming back, year after year, they’re doing really well here. They’re already starting to kill some of the trees where they were first released. We’re starting to see the first die-off.”
With that, members of the partnership will enter a new era in tamarisk control—an era of reclamation.