Tamarisk beetle (Diorhabda spp.) in the Colorado River basin: Synthesis of an expert panel forum

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Bloodworth, Benjamin R.; Shafroth, Patrick B.; Sher, Anna A.; Manners, Rebecca B.; Bean, Daniel W.; Johnson, Matthew J.; Hinojosa-Huerta, Osvel

Suggested Citation: 

Bloodworth, B.R., P.B. Shafroth, A.A. Sher, R.B. Manners, D.W. Bean, M.J. Johnson, and O. Hinojosa-Huerta. 2016. Tamarisk beetle (Diorhabda spp.) in the Colorado River basin: synthesis of an expert panel forum. Colorado Mesa University, Ruth Powell Hutchins Water Center, Scientific and Technical Report No. 1. 19 p.

In 2001, the U.S. Department of Agriculture approved the release of a biological control agent, the tamarisk beetle (Diorhabda spp.), to naturally control tamarisk populations and provide a less costly, and potentially more effective, means of removal compared with mechanical and chemical methods. The invasive plant tamarisk (Tamarix spp.; saltcedar) occupies hundreds of thousands of acres of river floodplains and terraces across the western half of the North American continent. Its abundance varies, but can include dense monocultures, and can alter some physical and ecological processes associated with riparian ecosystems.

The tamarisk beetle now occupies hundreds of miles of rivers throughout the Upper Colorado River Basin (UCRB) and is spreading into the Lower Basin. The efficacy of the beetle is evident, with many areas repeatedly experiencing tamarisk defoliation. While many welcome the beetle as a management tool, others are concerned by the ecosystem implications of widespread defoliation of a dominant woody species. As an example, defoliation may possibly affect the nesting success of the endangered southwestern willow flycatcher (Empidonax traillii extimus).

In January 2015, the Tamarisk Coalition convened a panel of experts to discuss and present information on probable ecological trajectories in the face of widespread beetle presence and to consider opportunities for restoration and management of riparian systems in the Colorado River Basin (CRB). An in-depth description of the panel discussion follows. 

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