These beetles help with invasive trees

Colorado officials have found a powerful ally in the war against the water-guzzling, fast-growing invasive tree tamarisk, which has overgrown stream banks across the West, including Fountain Creek and the Arkansas River basin.

Swarms of allies that are hungry and a long way from home.

On the Western Slope, the Colorado Department of Agriculture has had success in curbing the tenacious tree with Chinese beetles, which come from the same central Asian highlands as tamarisk, and have a taste for its leaves. Large stretches of the Dolores and Colorado rivers, once heavily infested with tamarisk, have been defoliated.

While one type of beetle - mountain pine beetle - threatens to destroy Colorado's lodgepole pine forests, this beetle could save its rivers and streams from another invader.

This summer saw the first large-scale releases of the Chinese beetles along Fountain Creek, as well as along the Arkansas near Lamar.

Officials hope other successes can be replicated here.

"The No. 1 benefit that immediately strikes people is cost. It's virtually free," said Dan Bean, director of the state's Palisade Insectary, where the beetles are bred. "Compared to going with bulldozers, it's way cheaper. The beetles defoliate the trees and they're extremely specific."

Tamarisk, also known as salt cedar, was brought to the U.S. in the 1800s as an ornamental tree and to protect stream banks from erosion.

But with no natural controls, it spread and began taking over river and stream banks. It has overtaken native cottonwoods along most of Colorado's rivers, and the Arkansas River is the most infested in the state, according to a 2006 report by the Grand Junction-based Tamarisk Coalition. Fountain Creek and the Huerfano River have the most tamarisk of any tributaries in the state.

It's not just biologists concerned. A single tree can consume 200 gallons of water a day, a huge amount of loss in the arid West. The report said the Arkansas River and communities that depend on its water, including Colorado Springs, are losing 53,834 acre-feet of water - more than 17 trillion gallons- a year to tamarisk.

Tamarisk is resistant and prolific, and new plants can grow from dead ones, so it can cost up to $1,000 an acre to remove, with yearly follow-up checks to make sure it is not re-growing.

In July , the state, working with the National Resource Conservation Service, released 8,500 beetles along Fountain Creek just north of Pueblo, in cooperation with a land owner. Another 18,000 were released a few weeks later.

Late-summer checks of revealed no beetles on the tamarisk, said conservation service biologist Patty Knupp."

"That's not to say they're not there. They weren't on our monitoring trees," Knupp said.

That's not unusual, said Bean, with the state insectary. It takes a year before beetles are stable and numerous enough to attack a tree. Once the tamarisk is gone, the beetles die.

In 1999, after more than a decade of study, the federal government approved the use of beetles for tamarisk control. Pueblo Reservoir, where some shores are lined with tamarisk, was selected as one of six test sites, with 1,000 beetles released in 2001.

Seven years later, the quarter-inch-long beetles are right at home. The tamarisk isn't dead, but a 100-acre area is defoliated, and the tamarisk has not spread, said Denise Hosler, botanist for the U.S. Bureau of Reclamation, which runs the reservoir.

"You can release the beetles and they don't actually kill everything but they do tend to hold it in a static state, so we don't see an increase in salt cedar populations," Hosler said.

The project has shown the beetles can survive the area's harsh winters and they don't attack other plants or pose a nuisance to people using the reservoir, she said. Monitoring will continue.

"This is an ongoing study. We're in the very early stages of trying to move them around. It does appear we have a sustainable population there and they are helping to keep the sprouts in a check sort of situation," Hosler said.

Colorado got in the beetle business in 2005, with beetles from entomologists in China and Kazakhstan. Small releases in Mesa County were successful, and beetles from the state insectary have been released on the Western Slope every year since. With its leaves gone, a tamarisk sucks just 5 percent of its normal thirst.

Along the Colorado and Dolores rivers, the beetles are migrating on their own across large swaths. Several other Western states are spreading the Chinese beetles, with mostly similar success.

"It doesn't always work. It's not a sure bet that you throw beetles out and you're definitely going to get some success," Bean said.

But one thing is for sure: "The beetles have come a long way."