The introduction of Tamarix spp. (saltcedar) into the United States has significantly impacted riparian ecosystems, including reduced biodiversity and altered fire and flood cycles. Due to the high costs and variable success associated with traditional controls, scientists and researchers hope to implement the widespread use of the biological control agent, Diorhabda elongata. Although Diorhabda is viewed as an ideal biological control agent due to its high host specifity and adaptability, successful establishment has been inconsistent across the Western United States. Certain Diorhabda populations have been able to successfully establish and control saltcedar in some U.S. locations, while other populations have struggled. Although this limited success could be due to a variety of environmental factors, host plant genetics and origin are thought to be very important in driving Diorhabda population dynamics. In this experiment, we look at a variety of species/biotypes of Tamarix grown in a common garden from different locations across the Western United States to determine how they will affect Diorhabda biology and population dynamics. Beetle fitness, including egg production, development rate and success, was measured by caging beetle egg clusters on individual branches in sleeve cages. The influence of Tamarix accessions on different Diorhabda elongata ecotypes will be presented. The implications of these differences on the potential establishment of Diorhabda populations in the future and the improved probability of predicting the success or failure of establishment will be discussed.