TOXICITY EVALUATION OF SINGLE AND CHEMICAL-MIXTURES OF ROUNDUP, GARLON-3A, 2,4-D, AND SYNDETS SURFACTANT TO CHANNEL CATFISH (ICTALURUS-PUNCTATUS), BLUEGILL SUNFISH (LEPOMIS-MICROCHIRUS), AND CRAWFISH (PROCAMBARUS SPP)

The acute toxicity of individual and mixtures of three herbicides (2,4 -D, Garlon-3A, and Roundup) and a chemical additive (Syndets surfactan t) was evaluated using three species of freshwater organisms (channel catfish, bluegill sunfish, and crawfish). Among the three herbicides, Roundup was more toxic to catfish and bluegill than Garlon-3A and 2,4- D. The order of toxicity in fish (Roundup > Garlon-3A > 2,4-D) was rev ersed in bioassays with crawfish, indicating a significant difference in interspecies (vertebrate vs invertebrate) biological variability. A djusted 96 h LC50's were 14.5, 13.0, and 21, 632.8 mg/L for Roundup, 1 09.5, 91.0, and 6,397.5 mg/L for Garlon-3A, and 181.2, 266.3, and 750. 1 mg/L for 2,4-D, for catfish, bluegill, and crawfish, respectively. F or Syndets surfactant, LC50 values of 1.9 mg/L (bluegill), 2.3 mg/L (c atfish), and 15.2 mg/L (crawfish) were recorded, indicating that this chemical additive was much more toxic than the three herbicides. Bioas says with herbicide mixtures resulted in combined toxic effects that w ere slightly antagonistic and/or additive. Lethal concentrations of he rbicide mixtures were found to be lower than recommended field formula tions, but it was anticipated that such hazardous amounts would be rar ely reached in roadside ditches where the presence of large volumes of water is likely to provide dilutions to levels that may not pose a th reat to aquatic life. (C) 1997 by John Wiley & Sons, Inc.