A Pilot Evaluation of the Toxicity of EarthTec® QZ on Invasive ( Bithynia tentaculata ) and Native ( Physa gyrina ) Snail Species from the Upper Mississippi River

We used a comparative approach to investigate the effects of a copper-based pesticide (EarthTec® QZ) on embryos of an invasive snail (Bithynia tentaculata) and a native snail (Physa gyrina). Embryos were exposed to one of three treatments: control (0 mg/L Cu2+), low-dose (0.1 mg/L Cu2+), or high-dose (0.6 mg/L Cu2+), which reflect manufacturer-recommended low and medium 4-day molluscicide treatment concentrations. Exposure to 0.6 mg/L Cu2+ over 4 days generated 100% mortality in both invasive and native snail embryos; however, reducing the exposure time from 4 to 1 day resulted in 100% mortality in B. tentaculata but some hatching (7%) in P. gyrina. In contrast, embryos of both species exposed to 0.1 mg/L Cu2+ treatment for 4 days showed almost 100% survivorship. Further manipulations of Cu2+ concentrations and exposure times may yield regimes that maximize mortality in B. tentaculata while minimizing negative impacts on native species.