title: Behavioral and physiological resistance to insecticides in the German cockroach (Dictyoptera: Blattellidae): an experimental reevaluation.
abstract: Although physiological resistance to pesticides has been demonstrated in German cockroaches, Blattella germanica (L.), behavioral resistance has not been shown clearly. To test for the possible development of behavioral resistance, choice-test experiments were done to determine whether adult males and females from physiologically resistant and susceptible strains differed in avoidance of three emulsifiable formulations (chlorpyrifos, cypermethrin, and chlordane). Physiological resistance was verified by estimation of LC50s. Within 6 h, each cockroach chose between an untreated and a treated harborage. In the resistant strain, both sexes avoided harborages treated with cypermethrin and survived the choice tests, but more females than males avoided harborages treated with chlorpyrifos and survived. In the susceptible strain, neither sex avoided harborages treated with cypermethrin or chlorpyrifos, and most died. The physiologically resistant strain was more resistant to chlorpyrifos and cypermethrin than was the susceptible strain, with females generally having higher LC50s. However, in choice tests with chlordane in which physiological resistance levels were similar between the strains, the strains did not differ in avoidance of treated harborages or survivorship. Avoidance of treated harborages may be facilitated by high levels of physiological resistance, but we detected no behavioral resistance traits. High levels of physiological resistance permitted cockroaches to absorb an amount of pesticide that led to detection and subsequent avoidance of treated harborages. Results of our study suggest that previous research on insects has not demonstrated the evolution of stimulus-dependent behavioral resistance in field populations exposed to pesticides.
authors.affiliation: Department of Zoology, University of Florida, Gainesville 32611-2009.
authors.forename: M E
authors.initials: ME
authors.lastname: Hostetler
authors.forename: R J
authors.initials: RJ
authors.lastname: Brenner
mesh_terms: D000818:Animals; D002706:Chlordan; D004390:Chlorpyrifos; D003058:Cockroaches / Q000502:physiology; D005260:Female; D007305:Insecticide Resistance / Q000502:physiology; D007306:Insecticides; D008297:Male; D011722:Pyrethrins
chemical_list: D007306:Insecticides; D011722:Pyrethrins; D002706:Chlordan; C017160:cypermethrin; D004390:Chlorpyrifos