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The tomato borer Tuta absoluta (Lepidoptera: Gelechiidae) is an invasive pest of tomato crops that is rapidly expanding around the world. It is considered a devastating pest and its control heavily relies on application of insecticides. Diamides are a novel class of insecticides acting on insect ryanodine receptors and are highly effective against lepidopteran pests. To date, chlorantraniliprole and flubendiamide have been registered in the market and they have been extensively used to manage T. absoluta. In this study, a survey was conducted in Greece and Italy monitoring diamide resistance. The populations originating from Sicily (Italy) exhibited LC 50 s that ranged between 47.6-435 for chlorantraniliprole and 993-1.376 for flubendiamide, while for Crete (Greece) LC 50 s ranged between 0.14-2.45 for chlorantraniliprole and 1.7-8.4 for flubendiamide (LC 50 s in mg L -1 ). Comparing this result to the susceptible reference strain, high resistance levels for the Italian populations were detected, i.e., up to 2,414-and 1,742-fold for chlorantraniliprole and flubendiamide, respectively. Resistance ratios for Greek populations were found up to 14-fold for chlorantraniliprole and 11-fold for flubendiamide, suggesting that diamide resistance is low but increasing considering monitoring data over time. Hereby, we report for the first time, cases of resistance development to diamide insecticides in T. absoluta. These findings underline the importance of committing to the resistance management strategies for diamide insecticides.

36Insect ryanodine receptors (RyR) are the molecular target-site for the recently introduced 37 diamide insecticides. Diamides are particularly active on Lepidoptera pests, including tomato 38 leafminer, Tuta absoluta (Lepidoptera: Gelechiidae). High levels of diamide resistance were 39 recently described in some European populations of T. absoluta, however, the mechanisms 40 of resistance remained unknown. In this study the molecular basis of diamide resistance was 41

Bemisia tabaci resistance evolved differently in each of the three insecticides studied. Imidacloprid resistance seems less established and less persistent than alpha-cypermethrin resistance. The low resistance levels for pirimiphos-methyl suggest absence of cross-resistance with other organophosphates or carbamates used.