Resistance levels to propargite in field populations of Brevipalpus yothersi (Acari: Tenuipalpidae) from Brazil's citrus belt

Brevipalpus yothersi Baker is a vector of citrus leprosis virus C (CiLV-C), the primary viral disease affecting orchards across the citrus belt of Brazil. Disease management is based mainly on the use of synthetic acaricides to control this mite, with propargite being one of the main acaricides currently in use. The objective of this study was to estimate the levels of resistance to propargite in field populations of B. yothersi. A direct contact bioassay was established on leaf discs of jack bean plants, exposing females to propargite for 48 h. The LC50 and LC95 values were determined for the susceptible laboratory population and for the field populations. In addition, ArcGIS software was used to spatially represent the resistance ratios found. The susceptible laboratory population presented LC50 and LC95 values of 34.97 and 87.70 mg L−1, respectively. Field populations showed LC50 values ranging from 15.35 to 94.54 mg L−1, with resistance ratios in LC50 between 0.44 and 2.70-folds that of the laboratory population, indicating low levels of resistance to propargite. Using ArcGIS, the geographic impact of the resistance status was visualized. Currently, the development of resistance to propargite in B. yothersi is low and can be prevented, allowing continued effective control of the vector. To maintain this situation, it is essential to implement resistance management strategies, such as the rotational use of acaricides with different modes of action, adapted to the characteristics of each region.