2006 Annual Report 4d.Progress report. This report serves to document research conducted under a Non-Funded Cooperative Agreement between ARS and Nature Diagnostics, Inc. of Blacksburg, VA. Additional details of research can be found in the report for the inhouse project 6408-41000-005-00D, Control of Undesirable Microbes and Off-flavors in Aquaculture with Natural Products. Nature Diagnostics, Inc., has developed one novel method for synthesizing the patented algaecide. The lead ARS scientist of this research project evaluated a sample of this novel algaecide as synthesized by Nature Diagnostics, Inc. Results from the bioassay evaluation found toxicity towards the odor-producing species of blue-green algae to be about 20 times less toxic than the algaecide when produced by the method outlined in the patent. Based upon chemical analysis of the sample provided by Nature Diagnostics, Inc., impurities are present in the sample and this may account for the reduced activity. Nature Diagnostics, Inc., plans to continue to refine their method to enhance recovery and purity of the end product. In addition, this commercial partner plans to develop other additional synthetic methods to develop a more cost-effective method for manufacturing the patented algaecide.