Abstract
Coccinellids beetles are considered one of the potential predators of the canola and mustard aphids. But the application of insecticides in field to manage aphids cause impairment of several key biological traits of the exposed coccinellids through physiological and behavioral effects. It is crucial to understand the effects of insecticides on the coccinellids. The current research was aimed at determining the intraguild predation (IGP) of different life stages combinations of Coccinella septempunctata and Coccinella transversalis in the presence and absence of prey and the impact of sublethal concentrations of insecticides on intra-guild predation (IGP) and aphid consumption by coccinellids. Data revealed that in the absence of prey larvae of C. septempunctata exhibited more predation on C. transversalis while the predation of C. septempunctata on C. transversalis was relatively less in the presence of prey. The larvae of C. septempunctata were found stronger and competitive than larvae and adults of C. transversalis during IGP. Higher IGP of C. septempunctata on C. transversalis was linked to its larger body size. Moreover, sublethal concentrations of insecticides (lambda-cyhalothrin, cypermethrin, thiamethoxam, imidacloprid, profenophos and chlorpyriphos) significantly affected the IGP of coccinellids beetles and their aphid consumption. The effect of insecticides was concentration dependent. None of the tested insecticides was found completely harmless to coccinellids. Imidacloprid was found relatively safe to coccinellids and hence, recommended for use in canola field. It is concluded that C. septempunctata is a stronger predator showing high value of IGP and the presence of prey affects the predation of C. septempunctata on C. transversalis. Sublethal concentrations of all test insecticides exert a negative impact on IGP and aphid consumption by both these coccinellids species. Imidacloprid is relatively safe for aphid control.