Studies on relative toxicities of six insecticides on epigeic earthworm, Perionyx excavatus

The 96 h LC(50) values of six insecticides were determined on a non-target epigeic earthworm Perionyx excavatus under laboratory conditions. Cypermethrin was found most toxic to P. excavatus (LC(50)-0.008 mg/kg), followed by endosulfan (LC(50)-0.03 mg/kg), carbaryl (LC(50)-6.07 mg/kg), chlorpyrifos (LC(50)-7.3 mg/kg), aldicarb (LC(50)-10.63 mg/kg) and monocrotophos (LC(50)-13.04 mg/kg). When these LC(50) values were compared with their respective recommended agricultural doses, aldicarb and carbaryl appeared more dangerous than other pesticides because of their lower LC(50) values than their respective recommended agricultural dose. Mean lethal time to cause 50% mortality at recommended agricultural dose (LT(50)) also indicated that aldicarb achieved the fastest LT(50) (26 h) followed by endosulfan (38 h) and carbaryl (44 h) indicating the danger of these pesticides to P. excavatus.