Estratégias no manejo de resistência de Plutella xylostella (Lepidoptera: Plutellidae) e de Spodoptera frugiperda (Lepidoptera: Noctuidae): Rotação de inseticidas e controle biológico com parasitoide

Abstract

The use of chemicals has presented flaws and cases of resistance for the control of Plutella xylostella (L.) (Lepidoptera: Plutellidae) and Spodoptera frugiperda (J.M. Smith) (Lepidoptera: Noctuidae). The objective of this study was to evaluate the susceptibility of Plutella xylostella (L.) (Lepidoptera: Plutellidae) populations in Serra da Ibiapaba-CE; the rotation of insecticides in the management of P. xylostella resistant to deltamethrin and Spodoptera frugiperda (J. M. Smith) (Lepidoptera: Noctuidae) resistant to metaflumizone; the possibility of cross-resistance between the insecticides used; the adaptive cost associated with the resistance e; the performance of Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) on the control of metaflumizone resistant S. frugiperda. In the experiments with P. xylostella four generations were evaluated: successive application of deltamethrin (D-Delta); successive application of chlorantraniliprole (D-CL); successive application of metaflumizone (D-MET); successive application of Bacillus thuringiensis (Bt) (D-Bt); alternation of insecticides and maintained in the absence of insecticides (D-Control). In the trials with S. frugiperda five generations were evaluated, being: successive application of metaflumizone (M-MET); successive application of spinetoram (M-ESP); alternation of the insecticides (M-Rotation) and maintained in the absence of insecticides (M-Control). With populations from each assays, it was generally evaluated biological parameters (viability and duration of the phases, pupal weight, sexual reason; the longevity of the adults, the daily and total fertility and the parameters of the fertility life table were estimated. For the T. pretiosum assays, cartons containing eggs of two populations of S. frugiperda, one resistant to metaflumizone and the other without exposure to the product, were exposed to the parasitoid females. It was evaluated: The percentage of parasitism; the percentage of emergency; sexual reason; the number of parasitoids emerged per egg and the longevity of adult parasitoids. As for susceptibility, all populations tested showed average resistance to deltamethrin. The populations showed no resistance to chlorantraniliprole, Bt and metaflumizone. Resistance frequency was increased when the populations of S. frugiperda and P. xylostella were exposed successively to only one insecticide. Alternating applications have significantly reduced the frequency of resistance over generations of pest arthropods. No cross-resistance was detected between the insecticides deltamethrin, indoxacarb and Bt. Populations of P. xylostella from treatments with successive exposure to insecticides reduced pupae weight, adult longevity, net reproduction rate and relative fitness. Similarly, a negative effect on the biological characteristics of S. frugiperda was observed in relation to the increase in egg incubation period, higher percentage of pupae deformation, larval and pupal period, reduction in the percentage of emergence and longevity of adults, in population parameters and relative fitness. For T. pretisoum, parasitism, emergence, number of parasitoids/egg, and longevity of S. frugiperda from the eggs resistance frequency population were observed. The application of insecticides in a successive way should be avoided and the alternation of active principles with different modes of action should be promoted in order to reduce the risks of resistance development, since populations of resistant pest arthropods are difficult to control and may also infer action of the natural enemy.