Existem custos adaptativos em Plutella xylostella (L.) (Lepidoptera: Plutellidae) resistente ao lufenurom?

Abstract

Plutella xylostella is the most important brassica pest in the world, the rapid evolution of resistance to different active ingredients is a major problem in its control. In Brazil the first report of resistance of this pest to lufenuron was in 2011. The objective was to evaluate the existence of adaptive costs (fitness) associated with resistance of P. xylostella to lufenuron. To this end, susceptibility bioassays were performed for the susceptible population REC. -S and resistant BZR-R as for their F1 and F1 'progenies and the resistant population after four generations without BZNS selection pressure, biological parameters between REC-S and BZR-R were evaluated and compared with life and fertility tables beyond effect of insecticide feeding on adults. The BZNS LC50 reduced 1.8-fold after four generations. The larval period was lengthened, and the pupal weight reduced to F1 and F1 'mainly. BZNS male survival was reduced. The mean generation time (T), intrinsic growth rate (rm) and population doubling time (TD) were different for REC-S, F1 and F1 '. F1 fitness values of 0.52 and F1 'of 0.64 were observed. After adults were exposed to field dose, longevity, oviposition period, fecundity and fertility of BEZ-R females, they were higher than those of REC-S, and survival of BEZ-R was higher than REC-S. The results suggest that there is no fitness associated with P. xylostella resistance to lufenuron; Lufenuron resistance is stable and probably recessive, heterozygotes have lower fitness than their parents, and lufenuron resistant populations have an advantage over susceptible populations at field dose exposure. However, studies on cross resistance profile, stability and inheritance model of this resistance still need to be clarified for greater success in the management of this pest.