Extensive pesticide usage in the Southern High Plains has led to the development of resistance in many
pest species, as well as some non-target organisms. Thamnocephalus platyurus derived from agriculturally
impacted watersheds are between two and three times less sensitive to commonly applied agrochemicals
than T. platyurus from native grassland watersheds. Biological mechanisms that convey such resistance
are currently unknown. This study identified the contribution of metabolic enzymes to T. platyurus pesticide
resistance using the synergists piperonyl butoxide (PBO) and S,S,S-tributyl phosphorotrithioate
(DEF) to inhibit cytochrome P450s or hydrolases, respectively. Inhibition of cytochrome P450s and hydrolases
partially restored cyfluthrin and DDT sensitivity in T. platyurus, suggesting other resistance inferring
mechanism(s) were also involved. However, inhibition of hydrolases with DEF completely restored methyl
parathion sensitivity in pesticide resistant T. platyurus. DDT resistance paralleled cyfluthrin resistance,
but did not for methyl parathion resistance. These data suggest that the primary mechanism for the
development of resistance to agrochemicals in T. platyurus is due to increased metabolic detoxification.
Extensive pesticide usage in the Southern High Plains has led to the development of resistance in manypest species, as well as some non-target organisms. Thamnocephalus platyurus derived from agriculturallyimpacted watersheds are between two and three times less sensitive to commonly applied agrochemicalsthan T. platyurus from native grassland watersheds. Biological mechanisms that convey such resistanceare currently unknown. This study identified the contribution of metabolic enzymes to T. platyurus pesticideresistance using the synergists piperonyl butoxide (PBO) and S,S,S-tributyl phosphorotrithioate(DEF) to inhibit cytochrome P450s or hydrolases, respectively. Inhibition of cytochrome P450s and hydrolasespartially restored cyfluthrin and DDT sensitivity in T. platyurus, suggesting other resistance inferringmechanism(s) were also involved. However, inhibition of hydrolases with DEF completely restored methylparathion sensitivity in pesticide resistant T. platyurus. DDT resistance paralleled cyfluthrin resistance,but did not for methyl parathion resistance. These data suggest that the primary mechanism for thedevelopment of resistance to agrochemicals in T. platyurus is due to increased metabolic detoxification.
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