First report of Tuta absoluta resistance to diamide insecticides

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.