Abstract
The cotton producers from southern Mato Grosso are currently experiencing control failure with the use of the use of insecticides against the cotton boll weevil Anthonomus grandis Boheman, the main pest species of this commodity. Therefore, the present study was designed to survey insecticide resistance and the associated likelihood of control failure among boll weevil populations in the region. Ten insect populations were sampled during the 2016/2017 season and subjected to time-mortality (contact) bioassays in glass vials impregnated with dried insecticide residues at their respective label rates. The three insecticides most frequently used in the region were surveyed: the organophosphate malathion and the pyrethroids beta-cyfluthrin and zeta-cypermethrin. The survival curves showed estimates of the respective median survival time (LT50) for each combination of insecticide and insect copulation. However, there were no significant differences in susceptibility among populations. The estimates of control failure likelihood for each compound at their respective label rates also indicated negligible risk of control failure with their use. These findings are consistent with time-mortality results indicating the lack of insecticide resistant populations at the surveyed sampling sites, suggesting that the reported field control failures result from other causes such as problems with insecticide application.
Highlights
Brazil is among the five largest cotton producers in the world and is one of the largest exporters of cotton (Ridley & Devadoss, 2012; 2014; Food and Agriculture Organization of the United Nation [FAOSTAT], 2013)
Notwithstanding, one factor limiting cotton expansion in Brazil is reduced yield resulting from pest attacks, by the boll weevil Anthonomus grandis Boheman (Coleoptera: Curculionidae) (Ribeiro et al, 2010)
The aim of this work was to survey and assess the occurrence of insecticide resistance, and to evaluate the risk of insecticide failure in populations of boll weevil sampled in the state of Mato Grosso
Summary
Brazil is among the five largest cotton producers in the world and is one of the largest exporters of cotton (Ridley & Devadoss, 2012; 2014; Food and Agriculture Organization of the United Nation [FAOSTAT], 2013). The main control method against the boll weevil is the use conventional insecticides, primarily compounds of the organophosphorus group and pyrethroids (Showler, 2007). These groups of insecticides were used to eradicate the boll weevil in the United States (Allen, 2008), and their use prevails in Brazil is (Azambuja & Degrande, 2014)
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