Bioefficacy of some insecticides and mixed formulations against mango mealy bug, Drosicha mangiferae (green)

Abstract

Contact toxicity of some insecticides and mixed formulations was determined against nymphs of Drosicha mangiferae by nymphal dip (LC50) and topical application (LD50) methods. The LC50 value of deltamethrin + triazophos was 0.00007% showing 4.28 and 5.71 times higher toxicity compared to novaluron + indoxacarb (0.0003%) and chlorpyriphos + cypermethrin (0.0004%), respectively at 24 hours after exposure (HAE) against 2nd instar nymphs (average wt. = 0.029 g/nymph). Chlorpyriphos + cypermethrin exhibited almost similar toxicity (LD50 = 1.8 and 1.7 pg/nymph) respectively at 12 and 24 HAE against 3rd instar nymphs (average wt. = 0.038 g/nymph); profenofos + cypermethrin resulted in LD50 of 2 pg/nymph at both 4 and 6 HAE, likewise ethiprole + imidacloprid at 48 and 72 HAE resulted in LD50 of 1.0 pg/nymph, respectively against 4th instar nymphs (average wt. = 0.078 g/nymph). The LD50 values of imidacloprid and monocrotophos were 545.0 and 588.0 pg/nymph, respectively at 6 and 12 HAE against 3rd and 2nd instar nymphs. Among SP insecticides, lambda-cyhalothrin was most toxic (LD50 = 0.03 pg/nymph) showing 33 times higher toxicity compared to least toxic cypermethrin (1.0 pg/nymph); alphamethrin and deltamethrin at 6 and 48 HAE resulted in similar amount of toxicity (LD50 = 0.5 pg/nymph) showing 12.5 and 16.66 times lower toxicity than lambda-cyhalothrin (0.04 and 0.03 pg/nymph) against 4th instar nymphs, respectively.