Combined action of carbaryl and phenthoate on a freshwater fish (Channa punctatus bloch).

The toxic potencies of carbaryl and phenthoate were studied on a freshwater fish, Channa punctatus, by evaluating the percentage kill at different concentrations of exposure. To determine the combined action of these compounds, LC studies were performed by using carbaryl (C) and phenthoate (P) mixtures in the 1:3, 1:1, and 3:1 ratios. The 48-hr LC50 values obtained by calculating the data with probit method were 8.71 ppm for carbaryl and 0.473 ppm for phenthoate. Similar values on the mixtures were 0.717, 0.741, and 0.750 ppm for 1:3, 1:1, and 3:1, carbaryl:phenthoate mixtures. The toxicities of carbaryl and phenthoate have been discussed in relation to sensitivity of the species and their interaction with the target enzyme. Effectiveness of the joint action of carbaryl and phenthoate was determined by measuring three different parameters: the CTC value, the V value, and the CI value. This analysis showed that 3C:1P combination exerted marked synergism, 1C:1P exerted moderate synergism, and 1C:3P showed moderate antagonism.