Suscetibilidade de Anthonomus grandis Boh. (Coleoptera: Curculionidae) e sobrevivência de inimigos naturais de pragas do algodoeiro a inseticidas

Abstract

The boll weevil, Anthonomus grandis Boh. (Coleoptera: Curculionidae), is the most important cotton pest in Brazil. Despite the cotton ecosystem harboring large complex of natural enemies insecticides usage is the main control method against boll weevil and other pests. This work evaluated the susceptibility of boll weevil to commercial insecticides in single or in mixture ready-to-use and the impact of seven selected insecticides from different chemical groups applied at highest and lowest recommended field rates to cotton pest control on six predators [Chrysoperla externa Hagen, Eriopis connexa (Germar), Euborellia annulipes (Lucas), Hippodamia convergens Guérin-Méneville, Podisus nigrispinus (Dallas), and Solenopsis invicta Buren)] and four parasitoids [Aphelinus gossypii Timberlake, Bracon vulgaris Ashmead, Telenomus podisi (Ashmead), and Trichogramma pretiosum Riley)], key species for cotton pest managment. The LC50s calculated to boll weevil varied from 0.004 to 0.114 g a.i./L, and the relative pontency estimated were 1.37 to 29.59-fold. Futher, boll weevil adults were more susceptible to lambda-cyhalothrin and thiamethoxam in single formulation compared to chlorantraniliprole, fenitrothion and esfenvalerate. The mixture ready-to-use of lambda-cyhalothrin+chlorantraniliprole resulted in sinergistic effect; while the remaining mixtures tested were antagonistics. Methidation caused 100% mortality of all tested natural enemies. Among the natural enemies, E. annulipes exhibited high survival rate across all remaining tested insecticides. In addition, all predators and parasitoids exhibited high survival exposed to pymetrozin and chlorantraniliprole dried residue. Lambda-cyhalothrin and thiamethoxam at highest and lowest field rates and chorantraniliprole at highest field rate caused high mortality to P. nigrispinus, S. invicta and H. convergens and to all parasitoids. Based on the results, only the mixture of lambda-cialotrina+chlorantraniliprole demonstrated potential to boll weevil control with the remaining mixture ready-to-use with potential of use when targeting different pest species simultaneously. Pymetrozin, chlorantraniliprole and spinosad caused overall low impact on tested natural enemies; hence, becoming options to cotton pest management.