Suscetibilidade de populações do bicudo-do-algodoeiro, Anthonomus grandis Boh. (Coleoptera: Curculionidae), a inseticidas

Abstract

Cotton in the Cerrados is an example of large-scale agriculture with adoption of technologies resulting in high yields and quality. However, characterisitcs of cotton ecosystem such as long phenology and cultivation during summer under a tropical weather results in the occurrence of multiple arthropod pests, which contribute to the most farming decisions. Within the pest complex, infestations of the boll weevil, Anthonomus grandis Boh. (Coleoptera: Curculionidae), cause significant yield losses wether not properly managed. As consequency of pest status, boll weevil control has relied on broad-spectrum insecticide against the adults. However, this addiction on broad-spectrum insecticides has been questioned, in especial, the lack of efficacy of pyrethroids and options of low impact insecticides to control boll weevil. In this study was tested the susceptibility of different populations of boll weevil to the pyrethroid beta-cyfluthrin, widely recommended compared to malathion. Furthermore, the impact of three insect growth regulators (IGRs) lufenuron, pyriproxifen, and methoxyfenozide on adult survival and reproduction, and the toxicity of the spinosyns (spinetoram and spinosad) to adult weevils. The low susceptibility of boll weevil to beta-cyfluthrin was verified for five populations from Cerrado resulting in resistance ratios up to 437-fold; while, two weevil populations from Semiarid were susceptible. Nonetheless, all populatios still susceptible to malathion. Among the IGRs and life history characteristics evaluated, only the egg viability was reduced for females contaminated with lufenuron, irrespective of females exposure before or after mating and male exposure. Both spinosyns were toxic to adult weevils with spinetoram exhibiting lower LCs compared to spinosad; produced mortality similar to malathion, and longer residual of control than malathion. About these data, we can conclude that: beta-cyfluthrin should be avoided to control boll weevil (i); among the IGRs, only lufenuron reduced egg viability (ii); and both spinosyns have potential to boll weevil control.