Disturbance of phosphatase and transaminase activities in grubs of the red palm weevil Rhynchophorus ferrugineus (Coleoptera: Curculionidae) by certain insecticidal compounds

Abstract

Serious damage of red palm weevil to date palm encourages its control by various measures. The present work was carried out to investigate the effects of some insecticides of different categories (Pyriproxyfen, Neemazal, and Spinetoram) on the activities of phosphatases (acid phosphatase; ACP, alkaline phosphatase; ALP) and transaminases (glutamic oxaloacetic transaminase; GOT, glutamine pyruvic transaminase; GPT) in both haemolymph and fat body of the red palm weevil Rhynchophorus ferrugineus 5th instar larvae. After 24-h treatment by sublethal concentrations LC50 and LC75: 1067.5, 2317.5 ppm (Pyriproxyfen), 14,600, 27,100 ppm (Neemazal), and 18.37, 88.60 ppm (Spinetoram). Depending on the present results, the enzyme activities in both haemolymph and fat body tissues had been altered. Spinetoram inhibited the activities of both phosphatase and transaminase enzymes in the two tissues with an exception for the transaminases in haemolymph tissue at LC50. On the other hand, Pyriproxyfen stimulated GOT activity in the two tissues but inhibited GPT activity with no exception. While, phosphatases were inhibited with few exception. Neemazal LC75 stimulated phosphatases in the two tissues while transaminases were fluctuated. Spinetoram exhibited the most potent compound for inhibiting the enzyme activities.