Adult Diorhabda elongata (Saltcedar Leaf Beetle)
Tamarix (aka saltcedar) is an invasive tree species that has colonized virtually all perennial drainage areas in the southwestern United States. In addition to being a huge consumer of precious water resources, saltcedar displaces native shrubs and trees, increases soil salinity within infested areas and boosts the fire potential of its new habitat.
In response to a growing need to control saltcedar along the Canadian River, Texas Agricultural Experiment Station began working with an insect that attacks only saltcedar in 2004. Also participating in this biological control initiative are the National Parks Service, Canadian River Municipal Water Authority, Texas Water Development Board, Texas Water Resource Institute and the US Bureau of Reclamation.
Dense saltcedar stand near the Canadian River in Oldham County
The defoliating beetle, Diorhabda elongata (pictured above), originates from several parts of Europe and Asia. TAES released beetles originally collected from Posidi, a town in Northern Greece whose climate is similar to the Texas High Plains. Since their release in early spring, 2004, beetles have established on saltcedar at Lake Meredith and have survived two Texas Panhandle winters, flooding, extreme heat and drought. Although it is early in the course of biological control (typically, one expects 3-5 years before seeing serious damage to a host weed by insect bioagents), all active stages of the beetle can be seen attacking saltcedar foliage.
Additional releases of D. elongata were made in Borger in 2006, this time originating from Uzbekistan. Studies have shown that beetles collected from different locations can have varying efficacy and establishment potential. Releasing insects from an alternative point of origin allows us to maximize the potential for establishment and success of this biological control agent in the control of Texas Panhandle saltcedar.
Diorhabda elongata larval feeding (above) causes mild damage to saltcedar (below left) to complete tree defoliation (below right).