Toxicidade relativa de inseticidas à joaninha Hippodamia convergens (Guérin-Méneville) (Coleoptera: Coccinellidae)

Abstract

Aiming to offer harmonization of biological and chemical controls, we evaluated the toxicity of chlorantraniliprole, lambda-cyhalothrin and dicrotophos to the lady beetle Hippodamia convergens (Guérin-Méneville) (Coleoptera: Coccinellidae). Chlorantraniliprole toxicity was determined through concentration-mortality bioassays to H. convergens, Alabama argillacea (Hübner) and Chloridea virescens (Fabr.) (Lepidoptera: Noctuidae), whereas lambda-cyhalothrin and dicrotophos were tested on three populations of H. convergens collected from localities with different historical usage of insecticide. Furthermore, we applied a mixture of lambda-cyhalothrin and dicrotophos on a resistant population of H. convergens, and evaluated the biological traits of three populations in absence of insecticide exposure. Contact with dried residues and ingestion of contaminated moth eggs showed similar toxicity to H. convergens, being topical application a less toxic route. The field rates (FRs) currently recommended against A. argillacea e C. virescens were 383- and 37-fold greater than their respective CL90s. Lady beetles from one population were highly resistant to both lambda-cyhalothrin and dicrotophos, but the other two populations were susceptible to both insecticides. Beetles from the resistant population treated with these insecticides in mixture exhibited similar mortality to those receiving only dicrotophos, but it was twice greater than those exposed to lambda-cyhalothrin alone. Egg fertility was superior for resistant H. convergens population, the only different biological trait across all populations evaluated. We concluded that both route of exposure and concentrations may affect toxicity of chlorantraniliprole to H. convergens, and suggested that current FRs against A. argillacea and C. virescens may provide adequate control of these pest species, although showing risks to H. convergens. Finally, we suggested that resistance to lambda-cyhalothrin and dicrotophos in H. convergens reflect their exposure history to these materials.