Tamarisk beetle introduction shows signs of progress, says BLM

GRAND JUNCTION — After three years of releasing leaf beetles to combat the invasive tamarisk tree along the Colorado and Dolores Rivers, officials are reporting a marked improvement.

The Colorado Department of Agriculture’s Palisade Insectary and the Bureau of Land Management recently announced these observations.

The research findings will improve the effectiveness of future beetle releases throughout the state by determining the best times of year, temperatures and even time of day to release the beetles, officials said in a news release.

Currently, tamarisks have been completely defoliated from Gateway to the state line on the Dolores River, and beetles can be found wherever there is tamarisk from McPhee Reservoir to the Utah state line. On the Colorado River, this is the first year of major defoliation in Ruby Canyon west of Loma, and there are large populations of beetles from Loma to the state line, the news release noted.

The BLM Grand Junction Field Office, in consultation with the USDA Animal Plant Health Inspection Service, provided five initial release sites in Mesa County in 2005 and provided the areas for the monitoring of tamarisk biocontrol to take place.  Since 2005, the Montrose BLM has also provided several sites along the Dolores River.

In 2009, the Insectary staff and BLM expect complete defoliation from Loma to the state line, and major beetle movement into the Grand Valley. Defoliated tamarisk are expected to begin turning brown by June 2009, the BLM said. Defoliation stresses the tamarisk, reducing competition with willows, cottonwoods and other desirable plants.