Resistência fisiológica e comportamental de populações de Sitophilus zeamais à permetrina, esfenvalerato e esfenvalerato + fenitrotiona / Physiological and behavioral resistance of populations of Sitophilus zeamais to permethrin, esfenvalerate and esfenvalerate + fenitrothion

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

The maize weevil, Sitophilus zeamais Motschulsky, 1855 (Coleoptera: Curculionidae) is considered the main pest of stored maize in Brazil and its control is achieved mainly by insecticides. The massive and intensive use of these compounds may lead to selection of resistant populations and consequently compromise the control efficacy of this insect pest in Brazilian storage facilities. This work was a survey of physiological and behavioral resistance to the insecticides esfenvalerate, permethrin and the insecticide mixture esfenvalerate + fenitrothion in 27 populations of S. zeamais collected in several Brazilian counties and Paraguay, and also investigated possible costs associated with this phenomenon. The insects were subjected to concentration-mortality bioassays to determine the lethal concentrations LC50 and CL95. The populations were also subjected to two walking trials on surfaces treated and untreated with dried insecticide residues for detection of behavioral resistance. We also determined the instantaneous rate of population increase (ri), maize consumption and body mass of individuals of each population. We also determined the respiration rate, as well as amylase and lipase activity of the insects from each population as an indication of their metabolic rate. The concentrationmortality bioassays indicated resistance ratios ranging from 0.63 to 66.65x for esfenvalerate, 1.00 to 5.02x for the insecticide mixture esfenvalerate + fenitrothion from 0.79 to 69.59x for permethrin compared with the susceptible standard population (Sete Lagoas). These results indicate a decrease in pyrethroid resistance in Brazilian populations of maize weevil compared with previous studies. The behavioral characteristics of walking in treated area varied among populations and sex. There was avoidance to permethrin- and esfenvalerate- treated surfaces by females from different populations. There was no correlation between physiological and behavioral resistance, indicating that physiological resistance is independent of behavioral resistance in the populations tested. There was no significant difference in the instantaneous rate of increase (ri), body mass and respiration rate among the insects. In contrast, there were significant differences in food consumption and amylase and lipase activity among populations. Therefore, we conclude that there was no fitness cost associated with levels of resistance observed in the populations studied.

ASSUNTO(S)

stored grain pests peritróides fitossanidade comportamento adaptative cost cross resistance resistência cruzada behavior pragas de grãos armazenados custo adaptativo pyrethroids

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