Me. Hostetler et Rj. Brenner, BEHAVIORAL AND PHYSIOLOGICAL RESISTANCE TO INSECTICIDES IN THE GERMAN-COCKROACH (DICTYOPTERA, BLATTELLIDAE) - AN EXPERIMENTAL REEVALUATION, Journal of economic entomology, 87(4), 1994, pp. 885-893
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 b
ehavioral resistance, choice-test experiments were done to determine w
hether adult males and females from physiologically resistant and susc
eptible strains differed in avoidance of three emulsifiable formulatio
ns (chlorpyrifos, cypermethrin, and chlordane). Physiological resistan
ce was verified by estimation of LC50s. Within 6 h, each cockroach cho
se between an untreated and a treated harborage. In the resistant stra
in, both sexes avoided harborages treated with cypermethrin and surviv
ed the choice tests, but more females than males avoided harborages tr
eated with chlorpyrifos and survived. In the susceptible strain, neith
er sex avoided harborages treated with cypermethrin or chlorpyrifos, a
nd 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 betwee
n the strains, the strains did not differ in avoidance of treated harb
orages or survivorship. Avoidance of treated harborages may be facilit
ated by high levels of physiological resistance, but we detected no be
havioral resistance traits. High levels of physiological resistance pe
rmitted cockroaches to absorb an amount of pesticide that led to detec
tion and subsequent avoidance of treated harborages. Results of our st
udy suggest that previous research on insects has not demonstrated the
evolution of stimulus-dependent behavioral resistance in field popula
tions exposed to pesticides.