Comportamento em populações de Sitophilus zeamais resistentes a inseticidas

• Autor(a) principal: Guedes, Nelsa Maria Pinho
• Data de Publicação: 2008
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/850
• topic: Sitophilus zeamais; Comportamento; Inseticidas; Sitophilus; Insecticidae; Insect behaviour; CNPQ::CIENCIAS BIOLOGICAS::FARMACOLOGIA::TOXICOLOGIA

The main control method used against maize weevil infestations in tropic regions is the use of insecticides, particularly pyrethroids, due to the lack of suitable control alternatives. Adaptative costs associated with insecticide resistance were reported in Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae). Pyrethroid-susceptible and resistant strains of maize weevil were used to assess the behavioral process and the ecological outcome of larval competition inside the grain and also the behavioral resistance and plasticity of adults of maize weevil exposed to increasing doses of deltamethrin. The number of eggs laid in a seed and the consequent number of hatched larvae guide the larval behavior within the seed determining its outcome scramble or contest. The low adult emergence in the maize weevil resulted from a contest process of competition with direct interference among the larvae for both strains studied. There was no reduction in body mass with increased competition in either strain, and they exhibited similar optimal clutch size (two eggs/seed). Feeding plasticity is a component of phenotypic plasticity not usually considered in insect strains adapted to insecticide-altered environments, but which may either accentuate or mitigate insecticide resistance. One susceptible and two pyrethroid-resistant strains of maize weevil were subjected to free-choice and no-choice tests with maize grains sprayed with increasing doses of deltamethrin. The resistant strains exhibited higher feeding avoidance with increased deltamethrin doses than insects from the susceptible strain when subjected to free-choice tests. In addition, the resistant strains performed better under sprayed grains and exhibited low levels of feeding deterrence (≤ 12%) than the susceptible strain (50%). Locomotion plays a major role determining insecticide exposure. The behavioral responses to deltamethrin-sprayed surfaces differ among the maize weevil strains. Such responses were dose-dependent for flight take-off (reducing with insecticide concentration) in two strains of maize weevil, but not for an insecticide-resistant strain, while walking response was dose-independent for all of the strains. Behavioral resistance was independent from physiological resistance with one resistant strain exhibiting higher rates of flight take-off, and the other resistant strain exhibiting lower flight take-off. Female mobility was similar for all strains, unlike male mobility. Males of each strain exhibited a pattern of mobility following the same trend of flight take-off.