Fitness costs associated with field-evolved resistance to chlorantraniliprole inPlutella xylostella(Lepidoptera: Plutellidae)

Abstract

Plutella xylostella (L.) is the most important pest of Brassicaceae worldwide, with a recent estimate of US$ 4-5 billion expenditure for the control of this insect. A case of very high resistance of this pest to chlorantraniliprole was recently associated with reduced efficacy in a Brazilian field of Brassica spp. Although diamide resistance has been characterized, the fitness of insects due to such resistance has yet to be examined. Therefore, in this study, biological parameters were assessed in both susceptible and resistant strains of P. xylostella subjected to sublethal chlorantraniliprole concentrations. The field strain showed high resistance to chlorantraniliprole (RR50=27,793-fold), although resistance rapidly decreased in the first generations, showing instability. The exposure of susceptible and resistant larvae to their respective LC1, LC10, and LC25 values led to an increased duration of the larval and pupae phases and reduced weight in both strains; however, no significant differences in pupal viability across the treatments were observed. The resistant insects presented significantly lower larval weight and fecundity and higher larval and pupal periods, hatchability, and male longevity when not exposed to chlorantraniliprole, suggesting a fitness cost associated with resistance. In addition, resistant females showed a significantly higher egg-laying period and longevity at LC25, whereas the males lived longer at LC1. Chlorantraniliprole negatively impacted the biological parameters of both strains tested, although these effects were more relevant to the resistant insects. Resistant P. xylostella showed negative and positive biological trade-offs when compared with the susceptible individuals in both the absence and presence of chlorantraniliprole. Despite the important role that these trade-offs may play in the evolution of resistance to chlorantraniliprole, practical applications still depend on such information as the dominance of fitness costs and resistance.

Rapid selection for resistance to diamide insecticides in Plutella xylostella via specific amino acid polymorphisms in the ryanodine receptor

“…Similar data has also been collected for susceptible field strains from Brazil (Ribeiro et al, 2014, da Silva et al, 2012) and Japan (Steinbach et al, 2015). …”

First report of Tuta absoluta resistance to diamide insecticides

“…A second key question concerning the Italian populations is on the resistance mechanisms in the particular environment. Studies in diamide resistant P. xylostella have shown that reversal of resistance may occur in absence of selection pressure (Wang et al 2013;Ribeiro et al 2014). On the other hand, other P. xylostella strains have shown long term stability suggesting absence of fitness cost (Steinbach et al 2014).…”

Novel mutations and mutation combinations of ryanodine receptor in a chlorantraniliprole resistant population of Plutella xylostella (L.)

“…However, intensive and repetitive use of the diamides have led to the rapid development of resistance in both P. xylostella and S. exigua 781014.…”