Beetle release targets invasive tamarisk

MONTROSE — The introduction of a beetle to combat invasive tamarisk in local riparian sites is beginning to show signs of effectiveness.

The Bureau of Land Management Uncompahgre Field Office (UFO) worked with the Colorado Department of Agriculture’s Palisade Insectary to release Diorhabda elongata deserticola Chen, the tamarisk leaf beetle, in July 2007.

The groups released 34,000 beetles in two releases last year, and a “boost,” at one site and one release at a new site this year, the BLM said. The beetles were released last summer at an undisclosed site along the Dolores River in western Montrose County.

Tamarisk plants in the Bedrock area are now showing some defoliation following the releases in 2007. Staff are working on establishment along the Gunnison River.

“Riparian sites, selected for release of the tiny beetle with a huge appetite for tamarisk leaves, have long since lost their native vegetation to decades-old growth of tamarisk,” the BLM noted. According to the agency, manually removing tamarisk stands can cost $1,500 to $3,000 per acre. By comparison, the tamarisk leaf beetle offers treatment of tamarisk stands for less than $10 per acre.

“By 2009, we expect to see large-scale defoliation of tamarisk at the release sites,” said Insectary Director Dan Bean in a statement. “With Diorhabda, we can be hopeful that waterways and riparian areas throughout the West will once again be prime habitat for native willows and cottonwoods.”

Years of research and interagency cooperation preceded last year’s release of the beetle.

“The Palisade Insectary, operated by the Conservation Services Division of the Colorado Department of Agriculture, plays an important role in the release and monitoring of the insect, which underwent more pre-release testing than any other biological control agent in U.S. history,” the BLM stated.

The Insectary has taken on a huge workload for the UFO, monitoring these sites and bringing invaluable, in-depth experience to the project, said BLM Uncompahgre Field Office Manager Barb Sharrow in a statement. “It is a great relationship we have going—good for both the Palisade Insectary and the BLM.”