The Conundrum of Chemical Boll Weevil Control in Subtropical Regions

Susceptibility of boll weevil to ready-to-use insecticide mixtures

“…Various practices are recommended to restrain boll weevil infestation in cotton fields, which are deployed preventively, including cultural, behavioral, and legislative enforcement methods (TORRES et al, 2015;NEVES et al, 2013;, but after field colonization its population suppression in large scale fields relies mainly on insecticide usage (SHOWLER, 2012;LIMA JUNIOR et al, 2013). Chemical control is the most applied method of cotton pest control in Brazil and in other major cotton growing regions worldwide (WU; GUO, 2005;NARANJO, 2009;WILSON et al, 2018).…”

“…In Brazil, boll weevil is responsible for the largest number of insecticide sprays against a single target pest species in cotton fields (LIMA JUNIOR et al, 2013;BÉLOT et al, 2016). Cost estimations of cotton pest control indicate boll weevil as the pest that most inflates costs; its presence in cotton fields determines the spray frequency and insecticide choice during spray decision (SHOWLER, 2012;BÉLOT et al, 2016). When boll weevil infestation reaches the economic threshold, at least five sequential sprays are carried out to attain control of adults emerging over 20 -25 days of the developmental period (from oviposition to adult emergence).…”

“…Nonetheless, these advances have generated more benefits in areas where insect pests of cotton are less diverse, compared to the cotton ecosystem in Brazil. The major cotton growing areas in Brazil have a large diversity of sucking pest species not targeted by Bt-cotton, lepidopteran larvae either unsusceptible or with low susceptibility to Bt toxins, even using pyramided traits (TORRES et al, 2009), and boll weevil, which is the worse cotton pest there can exist (SHOWLER, 2012).…”

“…The whole development, from eggs to adulthood, takes place partially protected inside cotton fruiting structures (COAKLEY et al, 1969). Besides inflating control costs, by requiring sprayings to reach adults from successive emergences (SHOWLER, 2012;LIMA JUNIOR et al, 2013), recommended broad-spectrum insecticides have a large impact on non-target arthropods, producing either resurgence, or secondary pest species outbreaks, such as mites (WILSON et al, 1998), aphids (GODFREY et al, 2000, and whiteflies (OLIVEIRA et al, 2001).…”