Field-evolved resistance of Liriomyza sativae Blanchard (Diptera: Agromyzidae) populations to insecticides with distinct modes of action

Liriomyza sativae (Blanchard) is a key pest of high-value crops such as melon and tomato, where chemical insecticides remain the primary control strategy. Increasing growers’ reports of control failure and shifts in susceptibility to cyromazine, cyantraniliprole, and spinetoram raise concerns about the sustainability of current management programs. This study assessed the susceptibility of L. sativae populations from major production areas in Northeastern and Southeastern Brazil using diagnostic concentrations, label rates, and concentration–mortality bioassays. Cyromazine mortality ranged from 7.7 to 93.0%, whereas cyantraniliprole remained highly effective (85.1–100%). Spinetoram exhibited substantial variability, with mortality ranging from 12.2 to 100%. Field-evolved resistance to spinetoram was confirmed in Arapiraca (ARP), Petrolina (PTL), Poções (PÇS), and Inhuçú (INH) populations. LC 50 values ranged from 5.53 to 86.61 mg a.i./L for cyromazine, 0.12 to 0.91 mg a.i./L for cyantraniliprole, and 0.03 to 44.16 mg a.i./L for spinetoram, with lethal ratios reaching up to 1652-fold relative to the most susceptible population. Overall, the results demonstrate heterogeneous susceptibility among Brazilian L. sativae populations and confirm resistance to cyromazine and spinetoram in several regions. These findings underscore the urgent need for proactive insecticide-resistance management to safeguard the long-term efficacy of key insecticides used against L. sativae .