Synergism in tertiary mixtures of pesticides

Two compounds, a pyrethroid , decis and a carbamate sevin both effective molluscicides against the snail demonstrate synergistic activity when mixed in a 1:46 ratio (decis:sevin). The observations show that the LC values decreases sharply. For example, the 96h LC10, LC50 and LC90 of decis decreases 272.72, 112.82 and 10.92 times respectively. When the esterase inhibitor MGK-264 is mixed with the binary mixture in a 1:46:5 ratio (decis:sevin:MGK) it was found that the lethality of the tertiary mixture was much higher than the binary mixture of decis and sevin. It seems that sevin and MGK-264, both being esterase inhibitors prevent the deactivation of the decis in the body of the snail and thereby increase the toxicity of the latter.