Relative efficacy of some insecticides against the field population of bean aphid (Aphis craccivora Koch.) and safety to the associated aphidophagous coccinellid complex occurring on Lathyrus, lentil and chickpea crops

Out of the five insecticides tested for their bio-efficacy against the field population of bean aphid (Aphis craccivora Koch.), cypermethrin (0.004%) proved most efficacious on all the three test crops, viz., Lathyrus (Lathyrus sativus L.), lentil (Lens esculenta Moench.), and chickpea (Cicer arietinum L.); whereas monocrotophos (0.04%) in Lathyrus, endosulfan (0.07%) and dimethoate (0.04%) in lentil, and dimethoate (0.04%) and monocrotophos (0.04%) in chickpea were evaluated as alternatives for cypermethrin (0.004%). The predatory coccinellid complex of Aphis craccivora consisted of seven species, the dominant one being Coccinella septempunctata Linn. Dimethoate (0.04%) proved most toxic to coccinellid grubs in all the three test crops, whereas cypermethrin (0.004%) followed by endosulfan (0.07%) both in Lnthyrus and 1entil; and endosulfan (0.07%) followed by fenvalerate (0.02%), and monocrotophos (0.04%) in chickpea crop proved relatively safe for the coccinellid predator. For the coccinellid adults, dimethoate (0.04%) in Luthyrus, dimethoate (0.04%) as well as monocrotophos (0.04%) in lentil, and monocrotophos (0.04%) in chickpea crop proved highly toxic. On the other hand, fenvalerate (0.02%) in Lulhyrus and lentil, and endosulfan (0.07%) as well as fenvalerate (0.02%) in chickpea crop caused minimum reduction in the coccinellid population. Taking both the grub and adult populations of coccinellid predators into account and from the risk/benefit ratio point of view, fenvalerate (0.02%) followed by endosulfan (0.07%) in Lnthyrus, cypermethrin (0.004%) followed by endosulfan (0.07%) in lentil, and endosulfan (0.07%) in chickpea crop proved less risky and more selective for aphid management.