Trade-off and adaptive cost in a multiple-resistant strain of the invasive potato tuber moth Tecia solanivora

Pesticide resistance in arthropods: Ecology matters too

Pesticide resistance development is an example of rapid contemporary evolution that poses immense challenges for agriculture. It typically evolves due to the strong directional selection that pesticide treatments exert on herbivorous arthropods. However, recent research suggests that some species are more prone to evolve pesticide resistance than others due to their evolutionary history and standing genetic variation. Generalist species might develop pesticide resistance especially rapidly due to pre‐adaptation to handle a wide array of plant allelochemicals. Moreover, research has shown that adaptation to novel host plants could lead to increased pesticide resistance. Exploring such cross‐resistance between host plant range evolution and pesticide resistance development from an ecological perspective is needed to understand its causes and consequences better. Much research has, however, been devoted to the molecular mechanisms underlying pesticide resistance while both the ecological contexts that could facilitate resistance evolution and the ecological consequences of cross‐resistance have been under‐studied. Here, we take an eco‐evolutionary approach and discuss circumstances that may facilitate cross‐resistance in arthropods and the consequences cross‐resistance may have for plant–arthropod interactions in both target and non‐target species and species interactions. Furthermore, we suggest future research avenues and practical implications of an increased ecological understanding of pesticide resistance evolution.

Inheritance and Fitness of Plutella xylostella (Lepidoptera: Plutellidae) Resistance to Chlorfenapyr

The diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), is a key pest of Brassicaceae worldwide. Populations have globally evolved resistance to various insecticides including chlorfenapyr, which was observed at high frequency in Brazil. We report the genetic characterization and fitness costs associated with chlorfenapyr resistance in a field-derived strain. The resistant strain (BZR-RR) and a susceptible strain (REC-SS) were used in both concentration-response bioassays and demography-based approach. Inheritance pattern of chlorfenapyr resistance was determined by conducting reciprocal crosses between susceptible and resistant strains, and by backcrossing. Next, life table analysis for the susceptible, heterozygotes, and resistant strains was performed to assess eventual fitness costs associated with chlorfenapyr resistance. Resistance of P. xylostella (BZR-RR) strain to chlorfenapyr was very high (RR50 = 421.58-fold) and also autosomal (no differences between reciprocal crosses), monofactorial and incompletely dominant (F1 pool DD = 0.26 ± 0.14). Dominance (h) was concentration dependent with 16 mg/l allowing at least 95% survival of the resistant heterozygotes. Recessive fitness cost was observed to be associated with resistance to chlorfenapyr. The relative fitness of heterozygotes (RS) and resistant homozygotes (BZR-RR) in comparison to the susceptible strain (REC-SS) was 0.91 and 0.23, respectively. Significant differences were found for many fitness components in the resistant homozygotes. Altogether, results suggest a rational use of chlorfenapyr in areas where susceptible populations still prevail, in parallel with the use of diagnostic concentrations (e. g., 20 mg chlorfenapyr/l), and rotation with different mode of actions, for which fitness costs of resistance are nonrecessive in P. xylostella.