The broader impact & commercial potential of this Small Business Innovation Research (SBIR) project is the ability to control zebra & quagga mussel infestations with a cost-effective and target-specific biological treatment. In addition to the estimated $7 billion economic impact, mussel infestation causes substantial ecological impacts. Currently, there is no treatment option available following infestation by quagga or zebra mussels functional at the scale of commercial reservoirs without significant disruption of native species. The successful development of an efficient and specific treatment has the potential to improve the ability to restore and protect native aquatic ecosystems, water infrastructure, power production infrastructure, and native fisheries. Additionally, the approach has the potential to lower production cost, and require a lower effective dose when compared to current treatment options. This SBIR Phase I project proposes to develop a biopesticide comprised of the enzymatic portion of a toxin for the mechanism of action and the binding domains from antibodies for targeting zebra and quagga mussels. Control of infestation by chemical means is largely restricted to enclosed systems, and requires additional remediation prior to water use. Biopesticides, however, can be considered a reduced risk treatment option. The use of ScFv (single chain variable fragment regions) from mAbs (monoclonal antibodies) has become common place in pharmaceuticals like Herceptin and MT-3724 and can be used here, resulting in a treatment product with anticipated high specificity, high efficiency, known mechanism of action, limited half-life, no expected long-term environmental impact, and limited to absent off-target impact. This work is believed to be novel as biopesticides utilizing immunotoxin technology for the remediation of aquatic nuisance species are not well developed. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.