Resistance status of Brevipalpus yothersi (Acari: Tenuipalpidae) to cyflumetofen and spirodiclofen in citrus orchards of São Paulo State, Brazil

The mite Brevipalpus yothersi Baker (Acari: Tenuipalpidae) is a vector of the citrus leprosis virus (CiLV-C, Cilevirus leprosis), the causal agent of citrus leprosis, which is the most important viral disease affecting citrus in Brazil. Leprosy management has primarily relied on synthetic acaricides to control the mite vector. However, the continuous use of the same active ingredients favors the evolution of resistance, consequently reducing control efficacy. This study aimed to monitor the susceptibility of B. yothersi populations collected from orchards in the citrus belt of São Paulo (SP), Brazil, to the acaricides, cyflumetofen and spirodiclofen, which are the main active ingredients currently used to control this mite. Discriminating concentrations of 0.72 mg L −1 cyflumetofen and 16.4 mg L −1 spirodiclofen were used to assess the susceptibility of mites. Significant differences were observed among the B. yothersi populations in response to both compounds. For cyflumetofen, three of the eight populations evaluated showed survival rates above 50%, with the highest survival rates (≥94%) recorded in populations from Colômbia, São Paulo. For spirodiclofen, nine of the fifteen populations evaluated showed survival rates above 50%, with the highest (93.8%) being observed in a population from Gavião Peixoto, São Paulo. These findings highlight the need for continuous resistance monitoring and rotation of modes of action, which may assist growers in implementing more effective resistance management programs and contribute to the sustainable control of this key pest in Brazilian citrus production.