Insecticide resistance mechanisms and their responses to insecticide selection pressures in the German cockroach, Blattella germanica (L.)
Abstract
Field and laboratory studies were conducted to characterize insecticide resistance mechanisms and their responses to insecticide selection in the German cockroach. In preliminary field studies, an insecticide mixture (lambdacyhalothrin + pyriproxyfen) was used to reduce an insecticide resistant cockroach population (Munsyana) by 80% over three generations. In survivors of insecticide treatments, oxidative enzyme (cytochrome P450) content, hydrolytic enzyme (esterase) activity, and insecticide tolerance increased significantly. Esterases and cytochromes P450 were subsequently purified from the pre-treatment Munsyana population (chlorpyrifos and cypermethrin resistant). Esterase purification identified both over-expression and potential qualitative adaptations which lead to a greater affinity for, and longer sequestration of organophosphate insecticides in comparison to the susceptible Johnson Wax strain. Antisera (anti-P450 MA) to purified cytochrome P450 (P450 MA) identified an over-expressed cytochrome P450 form(s) which catalyzes N-demethylation activity. Laboratory selections of a hybrid German cockroach strain (Johnson Wax x Munsyana) with either chlorpyrifos or cypermethrin led to significant increases in resistance to each insedicide. Chlopyrifos selected for the enhanced expression of an esterase electromorph (E2), and increases of total cytochrome P450 content, cytochrome P450-mediated N-demethylation activity, and P450 MA expression. Selection with cypermethrin also led to increases of total cytochrome P450 content, however, cytochrome P450-mediated N-demethylation activity and P450 MA expression decreased. Differential levels of cross-resistance occurred, as cypermethrin selected for cross-resistance to chlorpyrifos, however, chlorpyrifos selected for increased susceptibility to cypermethrin. In conclusion, overall results indicate a resistance management approach consisting of both insecticide rotation and mixture-based strategies. Specifically, a rotation-based approach utilizing chlorpyrifos, then cypermethrin, followed by a mixture of lambdacyhalothrin + pyriproxyfen is recommended as a resistance management strategy. This strategy, however, should be further researched under field conditions before it is recommended for use by pest management professionals.
Degree
Ph.D.
Advisors
Bennett, Purdue University.
Subject Area
Entomology|Pharmacology|Molecular biology|Genetics
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