Brevipalpus phoenicis (Geijskes, 1939) is one of the most important citrus pests in Brazil. Organotin acaricides represent more than 40% of the acaricide-treated citrus area for controlling B. phoenicis. For preserving the life-time of organotin acaricides, the objective of this research was to collect basic information for implementing a resistance management program of B. phoenicis to organotin acaricides in citrus groves from the State of São Paulo, Brazil. Initially, baseline susceptibility data of the susceptible reference population of B. phoenicis to fenbutatin oxide and cyhexatin were obtained with the use of a residual contact bioassay. Based on concentration-response data of this population to these acaricides, a diagnostic concentration of 180 mg of [AI] L-1 of distilled water was defined for both fenbutatin oxide and cyhexatin in order to be used in a program for monitoring the susceptibility of B. phoenicis to these acaricides. Then, a survey of the susceptibility to fenbutatin oxide and cyhexatin was conducted in 26 populations of B. phoenicis collected from citrus groves with different regimes of organotin acaricide use in the past five years. All populations showed susceptibilities to fenbutatin oxide and cyhexatin similar to the susceptible population; except for one population which showed a significant higher survivorship to cyhexatin (10,7%) than that for the susceptible population (1,92%) at the diagnostic concentration. Therefore, although the intense use of organotin acaricides in citrus groves from the State of São Paulo, the susceptibilities of B. phoenicis populations to fenbutatin oxide and cyhexatin are still very high.
Citrus; fenbutatin oxide; cyhebatin; resistance; pesticide