Early detection of resistance to acaricides in Tetranychus urticae Koch (Acari: Tetranychidae) populations is important for the implementation of efficient control methods. Current methodologies to detect resistance in the laboratory require exposure to acaricides for 24 to 72 h. Our objective was to design a reliable method faster than the current one. We modified the existing Insecticide Resistance Action Committee method to obtain results in less than 4 h. Experiments were conducted using a susceptible laboratory population of T. urticae and a field population from raspberry Rubus idaeus L., obtained in Tlazazalca, Michoacán state, Mexico. Susceptibility to the acaricides abamectin, acequinocyl, fenpropatrin, propylene glycol monolaurate, and bifenazate was evaluated. Reliable results were obtained in less than 30 min for all acaricides except bifenazate, for which results were obtained in 3.5 h. For abamectin, relative resistance (RR) of the field population compared with the susceptible colony achieved values of 13.99× (RR50) and 6.5× (RR95). For bifenazate, RR50 and RR95 values were 14.9× and 12.9×, respectively. For all other acaricides, the RR values were <10×.