Protect and Enhance the Nation’s Resource Base and Environment

Managing Invasive Species With Their Native Biological Controls

Issue (Who cares and why?)
     Saltcedar has taken over many of Nevada’s stream banks and lake margins, according to Tom Dudley, associate research professor in the Department of Natural Resources and Environmental Science at the University of Nevada.
      With roots that can seek groundwater as deep as 100 feet underground and the ability to drink water too salty for other plants, saltcedar (a.k.a. tamarisk) leaves other southwestern plants unable to compete. It spreads rapidly and can survive almost anything, from being submerged in water for more than a year to being consumed by wildfire.
      Originally brought to the U.S. as an ornamental plant and to stabilize soil, saltcedar is at least partially to blame for lack of adequate water flowing into a number of lakes in Nevada. Dudley says saltcedar has caused major economic damage to Nevada’s agricultural producers. Mechanically and chemically removing the plant is costly. “Farmers in Nevada area can’t economically justify the cost to control saltcedar, and they want to put the land back into production.”

What has been done?
     The newest enemy of the invasive saltcedar is a tiny leaf beetle called Diorhabda elongata. Researchers at the University of Nevada are finding that the beetle, from China, is successfully killing off the tree. The quarter-inch long beetle is a good biocontrol of saltcedar because both larvae and adults feed exclusively on the plant, and the adults produce two or more generations of offspring per year. They not only eat the green vegetation, but in doing so create holes in the leaves through which water escapes, causing branches to wither and die.
      The beetle was first introduced to Nevada inside multiple enclosed areas across several ecosystems so that researchers could study the effects beetles had on saltcedar. The beetles were then introduced to the wild in Pershing County, Nevada 2002. To date, scientists are following the beetle’s movements and survivorship along with saltcedar’s reactions to being defoliated.

Impact
      According to Dr. Dudley, using the beetles has obvious advantages over bulldozing the saltcedar. It is less disruptive and can easily treat a large area. Except for the cost of the research, it is basically free, whereas mechanical clearing costs $1,000 to $5,000 per acre.
      Dr. Dale Devitt, a University of Nevada professor of soil and water based in Las Vegas noted that if, through removal or defoliation of saltcedar, the trees' water consumption could be reduced by half, an extra 50,000 acre-feet of water per year could make its way to Lake Mead. That's enough water to supply 125,000 people.
      Allen Brinkerhoff a local grower in Pershing County, NV, said he is thrilled by the results the beetles have had on the saltcedar on his land. "They have done a good job. The effect is amazing." Two years ago the beetles defoliated 25-30 acres of Brinkerhoff’s land and they now have defoliated over 1,000 acres of land.
      The beetle is the first approved by the USDA as biological control agent for saltcedar in the United States.

Contact
Tom Dudley
Natural Resources and Environmental Science /186
University of Nevada
Reno, Nevada 89557