Controlling Water-Thirsty Saltcedar
Biological methods using imported leaf beetles are a hot topic
By Danielle Supercinski
Along the Rio Grande and Pecos River in Texas, saltcedar control methods vary from chemical to mechanical control. Biological control using leaf beetles, Diorhabda elongata, is a hot topic throughout these regions and other areas throughout Texas and the United States.
Dr. Mark Muegge, associate professor and Texas Cooperative Extension entomologist at Fort Stockton, has begun preliminary studies using leaf beetles imported from Central Asia and the Mediterranean area as a biological control for saltcedar at specific locations along the Pecos River ecosystem in Texas.
“Both adults and the immature stage, or larva, feed on the leaves and tender bark of saltcedar trees, and if beetle populations are high enough, they can completely defoliate a tree,” Muegge said. “Although the saltcedar tree will refoliate, this requires the tree to use the stored energy it has in its roots. Repeated defoliation by the beetles eventually causes stunting, death of limbs and finally tree death.”
Death of a saltcedar tree requires two or more years of defoliation by the beetles depending on the size and health of the tree, he said. There is very little risk of these beetles feeding on native plants because it has also been found that the beetle has no alternate source of food than saltcedar, except for another closely related species used as a shade tree in Mexico.
The preliminary studies Muegge is conducting will demonstrate the effectiveness of this method. Biological control is a less expensive and more natural method to rid streams and lakes of this water-thirsty invader than current chemical and mechanical control methods. Using the leaf beetles provides a new method that may be used alone or in combination with chemical and/or mechanical treatments.
“Biological control of saltcedar is not a replacement for other control methods such as chemical and mechanical control, but an additional tool that will aid in our efforts to control saltcedar,” Muegge said.
Muegge’s study is a pilot project as part of the Rio Grande Basin Initiative (RGBI). Other scientists throughout the state are working on similar biological control studies as well.
Dr. Jerry Michels, entomologist at the Agricultural Research and Extension Center at Amarillo, is working on biological control of saltcedar farther north at Lake Meredith on the Canadian River. Dr. Allen Knutson, Extension and research entomologist at Dallas, and Dr. Jack DeLoach, entomologist with the USDA-Agricultural Research Service at Temple, have successfully established field nursery sites for rearing saltcedar beetles in the Upper Colorado River watershed, near Big Spring.
A more detailed description of these projects can be found in Texas Water Resources Institute’s Summer 2006 “tx H2O” newsletter Vol. 2, No. 2, available at http://twri.tamu.edu/newsletters.php. For more general information on biological control of saltcedar, visit http://tcebookstore.org/pubinfo.cfm?pubid=1854 to view the Texas Cooperative Extension brochure.
As part of RGBI efforts, Texas Water Resources Institute and other partners throughout both New Mexico and Texas are seeking additional federal support to expand this program.
