pyrimidinones and indoxacarb

Insect pests, including the German cockroach, Blattella germanica (L.), are prone to the development of physiological resistance when exposed to a number of insecticide sprays, and cross-resistance is frequently observed. Toxic baits are often used as a primary method of controlling German cockroaches, also resulting in heavy selection pressure from insecticidal baits. In response to this pressure, cockroach populations have developed aversion to specific inert ingredients in bait. Here, we examined the effect of exposure to baits containing fipronil, indoxacarb, or hydramethylnon on the development of physiological resistance to the same and other insecticides in a number of German cockroach strains. We found that prolonged exposure to baits containing fipronil or indoxacarb increased physiological resistance to these compounds. However, no increase in physiological resistance against any insecticide was observed in response to exposure to hydramethylnon bait. Additionally, we found that exposure to fipronil bait increased cross-resistance to indoxacarb. On the other hand, exposure to indoxacarb bait did not increase cross-resistance to fipronil. Neither fipronil nor indoxacarb bait exposure increased resistance to hydramethylnon. Interestingly, the development of insecticide resistance in response to bait exposure was strain-dependent and influenced by bait palatability. Our results demonstrate that exposure to toxic baits, particularly those containing fipronil, plays a significant role in the development of insecticide resistance, including cross-resistance, in German cockroaches. Further, although insecticide resistance in response to baits is mediated by exposure through the oral route, the molecular mechanisms at play are likely different for each insecticide.

Topics: Animals; Blattellidae; Insecticide Resistance; Insecticides; Oxazines; Pheromones; Pyrazoles; Pyrimidinones

Bait formulations are considered to be the most effective method for reducing German cockroach (Blattella germanica) infestations. An important property of some bait formulations is secondary kill, whereby active ingredient (AI) is translocated in insect-produced residues throughout the cockroach population, especially affecting relatively sedentary early-instar nymphs.. B. germanica was collected from a location where baits containing hydramethylnon, fipronil or indoxacarb had become ineffective, and these AIs were topically applied to adult males. Results revealed the first evidence for hydramethylnon resistance, moderate resistance to fipronil and extremely high resistance to indoxacarb. Insecticide residues excreted by field-collected males that had ingested commercial baits effectively killed nymphs of an insecticide-susceptible laboratory strain of B. germanica but failed to kill most nymphs of the field-collected strain.. We report three novel findings: (1) the first evidence for hydramethylnon resistance in any insect; (2) extremely high levels of indoxacarb resistance in a field population; (3) reduced secondary mortality in an insecticide-resistant field-collected strain of B. germanica. We suggest that, while secondary mortality is considered to be advantageous in cockroach interventions, the ingestion of sublethal doses of AI by nymphs may select for high insecticide resistance by increasing the frequency of AI resistance alleles within the population. © 2015 Society of Chemical Industry.

Topics: Animals; Blattellidae; Insect Control; Insecticide Resistance; Insecticides; Male; Nymph; Oxazines; Pyrazoles; Pyrimidinones