Saltcedar (Tamarix spp.) is an invasive riparian shrub/tree in the western US that displaces native plants, increases soil salinity and wildfires, and lowers water tables. Diorhabda elongata feeds exclusively on saltcedar in Europe and Asia. The biological control potential of seven ecotypes is being tested: Fukang and Turpan, China; Chilik, Kazakhstan; Thessaloniki and Crete, Greece; Karshi, Uzbekistan; and Tunis, Tunisia. The Fukang ecotype is being released and defoliating large acreages of saltcedar at research sites in the northern half of the western US. In the southern half the Crete ecotype is being released. Although different ecotypes have been released in the western US, the effects of hybridization between ecotypes need to be understood before deliberately mixing ecotypes. All ecotypes will hybridize in controlled settings when not given a choice of mate. Some of these hybrids produce sterile offspring which could disrupt long-term population dynamics in field populations. The objective of this research was to determine if beetles in a population of two or more ecotypes will mate only with their own ecotype or will mate with any other ecotypes. The Crete ecotype was tested with Tunis, Karshi, Fukang and/or Turpan ecotypes. Tests were conducted in a controlled, small caged environment, differing in male and female ratio, in a controlled, larger caged environment, differing in ecotype numbers, and in a large controlled, open greenhouse. Pure-breeding and cross-breeding was observed in testing Crete ecotypes with other ecotypes. Implications for biological control will be discussed.