Saltcedar beetles introduced to help control the water-consuming, invasive saltcedar tree along the Upper Colorado River have defoliated 18 acres of a saltcedar stand, an increase in defoliation of 10 times each year for 3 years, according to a researcher involved in the project.
“We expect the beetles to begin actually killing trees in 2 more years but, in the meantime, the damaged trees are so small that they use little water and allow the grass to return,” said Dr. Jack DeLoach, entomologist with the U. S. Department of Agriculture-Agriculture Research Service (USDA-ARS). He said researchers expect this rate of increase to continue for several years.
DeLoach said this increase was a remarkable early successful control. “We expect that we can provide the beetles to landowners to control saltcedar on their own lands beginning next year,” DeLoach said.
Saltcedar was introduced to the western United States in the 1800s from central Asia as an ornamental tree and planted along riverbanks for erosion control. Without a natural predator, the tree soon out-competed native plants and has now infested an estimated 500,000 acres of Texas streams and riverbanks. The beetles are used as a companion to other methods of saltcedar control, including herbicide treatment and controlled burning.
DeLoach, Dr. Allen Knutson, an entomologist at Texas Agricultural Research and Extension Center at Dallas and other scientists from Texas Agricultural Experiment Station, Texas Cooperative Extension and USDA-ARS have worked to introduce saltcedar beetles from Greece to research sites near Big Spring. In 2004, the researchers released 38 adult beetles from Crete, Greece onto saltcedar trees. “They reproduced to about 500 by mid-July and defoliated 2 small trees, when we released the remaining 500 beetles from the cage with them,” DeLoach said.
They over wintered well in the open underneath the saltcedar trees, he said, and by September 2005 these beetles had increased to an estimated 200,000 and defoliated 210 trees in 1.6 acres of the saltcedar stand. By September 2006 they had defoliated 18 acres.
“We expect biological control to provide effective, safe, inexpensive, permanent and environmentally friendly control of saltcedar in areas where the beetles are adapted to the habitat and climate” he said. “We have tested these beetles for over 10 years and demonstrated that they are safe. They damage only saltcedars (in the plant genus Tamarix) and no species of Tamarix are native in either North or South America.”
For more information, see the article “Natural Predator: Foreign beetle shows promise for controlling saltcedar,” at http://twri.tamu.edu/news/2006/06/29/natural-predator/.
