Abstract
The German cockroach (Blattella germanica L.) is a worldwide pest that lives exclusively in human environments. B. germanica threatens human health by producing asthma-triggering allergens, vectoring pathogenic/antibiotic-resistant microbes, and by contributing to unhealthy indoor environments. While insecticides are essential for reducing cockroach populations and improving health outcomes, insecticide resistance has been a consistent barrier to cockroach control since the 1950s. We conducted seminal field studies to compare three insecticide resistance intervention strategies for cockroaches and evaluated resistance evolution across multiple generations. Using pre-treatment resistance assessment to drive decisions, we found that single active ingredient (AI) treatments can successfully eliminate cockroaches if starting resistance levels are low. We further established that rotation treatments intuitively reduce selection pressure, and are effective when insecticides with no/low resistance are used. We also found that mixture products containing thiamethoxam + λ-cyhalothrin AIs were universally ineffective and highly repellent; and finally, evolution of cross-resistance among AIs is a significant, previously unrealized challenge.
Highlights
B. germanica is a worldwide urban pest species that lives entirely in human settings
Broad resistance to most available insecticide classes was identified at both study sites based on pre-treatment resistance assessments (RAs) for 14 active ingredient (AI), including: indoxacarb, abamectin, boric acid, beta-cyfluthrin, bifenthrin, λ-cyhalothrin, fipronil, dinotefuran, imidacloprid, acetamiprid, clothianidin, thiamethoxam, chlorfenapyr and hydramethylnon[38]
Insecticide products with AIs having lowest resistance levels were chosen for application in the field study, i.e., abamectin (Avermectin class; IRAC category 6), boric acid (Inorganic class; IRAC category 8), thiamethoxam (Neonicotinoid class; IRAC category 4)
Summary
B. germanica is a worldwide urban pest species that lives entirely in human settings. B. germanica and other cockroaches impact human health through production of asthma and rhinitis-triggering allergens, vectoring of enteric pathogens and by causing psychological stress. Sensitization to cockroach allergens is one of the strongest risk factors for the development of asthma in low-income urban populations worldwide. Insecticide resistance has occurred to every insecticide class introduced for cockroach control since the early 1950s25–31. This is because B. germanica lives in relatively closed populations[32,33] which facilitates rapid selection for high-level resistance[28,34]. Cockroach baits have been revolutionary for both controlling cockroaches and reducing pesticide loads in urban housing[24,35], but baits have not been immune from resistance[29,36,37]. B. germanica populations tested in this study, but findings presented here provide some initial insights for future characterization
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