Estabilidade da resistência à lambda-cialotrina em Eriopis connexa (Germar) (Coleoptera: Coccinellidae)

Abstract

In the current study was investigated the stability of the resistance to lambda-cyhalothrin in the lady beetle Eriopis connexa (Germar) (Coleoptera: Coccinellidae). One resistant population (R-SEL) was maintained under selection pressure, while one subpopulation from R-SEL was reared without selection pressure (R-NSEL) during eight generations and compared with R-SEL and the population reference for susceptibility (SUS). The resistance ratio (RR) declined 2.10-fold for R-NSEL at 4th-generation after relieving the selection pressure, but maintained stable after when determined at 8th-generation compared to R-SEL. Likewise, alpha and β sterases activity measured at 8th-generation also declined in R-NSEL. The decreased in the resistance of R-NSEL observed at 8th-generation after relieving selection pressure was not enough to return to the susceptibility status (39-fold RR compared to SUS). The decline in the resistance level and activity of detoxifying enzymes did not reimburse the fecundity, which still being ~50% lower for females R-NSEL compared to females SUS. Yet, in the current study was characterized the susceptibility of a recently field-collected population of E. connexa (SUS-C), what allowed to investigating the performance of SUS-CxR-SEL progenies. The RR was ~200-fold between R-SEL and SUS-C. Furthermore, developmental time from larva to adult for SUS-C was 6 days delayed and adults were smaller compared to R-SEL and to the progenies from SUS-CxR-SEL. The egg production did not differ across parental populations and progenies, although numerically females from SUS-C and progenies from SUS-CxR-SEL produced more than 130 eggs, tallied during 35 days, than females R-SEL. Survival of adults from R-SEL and progenies from SUS-CxR-SEL, exposed to dried residues of lambda-cyhalothrin, varied from 77.4 to 100%, while adults from SUS and SUS-C exhibited null survival. Our data suggest that R-NEL exhibited stable resistance to lambda-cyhalothirn after eight generations without selection pressure. Furthermore, progenies from SUS-CxR-SEL gain benefits regarding development and reproductive output, and still owning resistance level enough to survive insecticide exposure similarly to their parental RSEL.