Potential of chemical insecticides on fourth larvae instar of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

Abstract

Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) is an important pest of Brazilian agriculture, whose management is oriented mainly towards controlling larvae. The objective of the research was to analyze the effect of chemical insecticides on fourth instar larvae of H. armigera. The research was conducted under laboratory conditions, corresponding to the treatments control, zeta-cypermethrin (37.5 mL /500 L); lambda-cyhalothrin (75 mL/ 150 L); chlorpyrifos (1.0 L / 300 L); bifenthrin + carbosulfan (1.0 L / 350 L); and beta-cyfluthrin (60 mL / 250 L). The bioassays were conducted in plastic containers containing an artificial diet. After treatment applications on the food substrate, and subsequent drying, two larvae were inserted per container, the set of four containers being considered a replicate, totaling four replicates per treatment, with mortality evaluations after 24, 48, 96 and 144 h after the applications. The sublethal effect was analyzed by evaluating the average weight of larvae and pupae (g), and emergence of adults (%). The active ingredients chlorpyrifos and bifenthrin + carbosulfan caused 100% mortality of fourth instar larvae of H. armigera from 48 h after the applications. After 96 h of phytosanitary application, lambda-cyhalothrin was responsible for causing mortality above 80%. Regarding the sublethal effect, better results were observed in the lambda-cyhalothrin and beta-cyfluthrin treatments, influencing the average weight of the larvae and the emergence of adults. The active ingredients chlorpyrifos, bifenthrin + carbosulfan and lambda-cyhalothrin are potential insecticides in the management of fourth instar larvae of H. armigera.