Impact of Diuron Applications to Commercial Catfish Ponds on Musty-Odor Cyanobacteria, Musty Off-Flavor Compound Concentrations, and Channel Catfish Fillet Flavor Quality

Abstract “Musty” off-flavor in pond-raised Channel Catfish Ictalurus punctatus can result in an unpalatable and unmarketable product for catfish farmers in the southern United States. Certain species of cyanobacteria (blue-green algae) in the catfish ponds produce 2-methylisoborneol (MIB), which accumulates in the Channel Catfish flesh and causes musty off-flavor. One management approach available to United States catfish farmers is the application of algicides to ponds to reduce the abundance of noxious cyanobacteria. Diuron is one approved algicide to specifically manage MIB-related off-flavor caused by the common cyanobacterium Planktothrix perornata f. attenuata. In this study, three commercial ponds determined in the early summer to contain musty off-flavor Channel Catfish were monitored over approximately 2 months to determine the impact and pattern of weekly diuron applications on the abundance of P. perornata, chlorophytes (green algae), MIB concentrations in the pond water, and flavor characteristics of the sampled Channel Catfish collected during the treatment period. After several diuron applications to each pond, the abundance of P. perornata and MIB concentrations in pond water decreased dramatically. Channel Catfish in each pond were determined to be “on-flavor” approximately 2 months after the initial diuron application. This study demonstrates that diuron applied via label-specified treatment protocols provides catfish farmers with a practical management approach for P. perornata and subsequent MIB-related off-flavor.