A year after beetles developed by scientists were released in selected tamarisk infestations at three sites in Colorado, the project is showing encouraging signs that the bugs will significantly defoliate the water-sucking trees that clog most Western rivers.
"It's still wait and see, but so far it's very encouraging," Dan Bean, manager of the Palisade Insectary, which helped develop the tamarisk leaf beetle, said Thursday. "If everything goes well, we'll see significant effects in two years."
Bean said 8,000 tamarisk leaf beetles, released last August in Horsethief Canyon west of Grand Junction, along the South Platte River in Adams County open space and at Bonney Reservoir in Yuma County, are taking hold and not being eradicated by ants, their main predators.
Releases in 2001 at four sites, two in Nevada and two in Utah, have matured and beetles are defoliating hundreds of acres of tamarisk. Bean also said that beetles released in 2004 near Moab, Utah, are taking hold.
The tamarisk, a tree native to Eurasia, has crowded out native species such as willows and cottonwoods and sucked up vast amounts of water in the West.
Mr. Bean was even more enthusiastic in the April issue of the Tamarisk Coalition Newsletter (pd and, yes, f):
Beetles released at the experimental field site near Delta, Utah were originally collected from a site near the town of Chilik, Kazakhstan . . . . The most spectacular successes for these Kazak beetles have occurred along the Colorado River near Moab, Utah. In 2006 beetles defoliated at least 18 river miles of dense tamarisk stands both upstream and downstream from Moab, after having defoliated only 2-3 total acres in 2005.The Rocky continues:
Labor-intensive efforts to eradicate tamarisk cost $1,500 to $3,000 per acre. The tamarisk leaf beetles may be able to do the job for less than $10 per acre, according to U.S. Bureau of Land Management spokeswoman Mel Lloyd.Those labor-intensive efforts are cutting, burning and poisoning--sometimes all three on the same stand.
The beetle, officially Diorhabda elongate deserticola Chen, has undergone more prerelease testing than any other biological control agent in the country's history, Bean said.
The BLM and the Palisade Insectary, operated by the Colorado Department of Agriculture, both play a role in the release and monitoring of the insect.
"They're slow and steady, but doing well," Bean said.
Sort of before: that's all tamarisk back there (Green River photo courtesy John G. Martin).
And sort of after: a pic blown up from the newsletter:
Crummy pic, and it may look better with the greenery from a distance, but tamarisk is a devil weed.