Field-Evolved Resistance and Cross-Resistance of Brazilian Tuta absoluta (Lepidoptera: Gelechiidae) Populations to Diamide Insecticides.

Tuta absoluta (Meyrick), one of the most important tomato pests worldwide, is heavily controlled by the application of insecticides. Diamide insecticides represent a new class of products recently registered to control T. absoluta After 6 yr of use, control failures have been reported in populations of this pest, suggesting a hypothetical resistance development. Therefore, a resistance survey was performed using nine populations of T. absoluta that were collected in open fields, including from areas with reports of a reduced efficacy of diamides in the Northeast and Central regions of Brazil. Initial surveys with diagnostic and label doses proved the reduced efficacy of diamides against most populations. The LC50 values of chlorantraniliprole varied from 0.0044 (Brasília) to 1,263 (América Dourada) mg AI liter-1 (the resistance ratios [RR50] ranged from 1.0- to 288,995-fold), whereas the LC50 values for cyantraniliprole and flubendiamide, respectively, varied from 0.015 (Brasília) to 281 (América Dourada) mg AI liter-1 and from 0.038 (Guaraciaba do Norte) to 3,018 (Gameleira 1) mg AI liter-1 The resistance ratios (RR50) ranged from 1.0- to 18,423-fold for cyantraniliprole and from 1.0- to 80,413-fold for flubendiamide. The log LC50 values of pairwise diamides were strongly and significantly correlated, which denoted cross-resistance among them. Very high resistance to diamides in T. absoluta was observed in this study, suggesting that strategies to mitigate resistance and thereby control the pest must not include only insecticides. Other control tactics must be carefully implemented over time to increase the life span of diamides, including rotational practices with other molecules.