This study was proposed with the aim to establish in Colombia a standard methodology to evaluate the level of sensitivity of fungi and oomycetes to QoI fungicides. The used model was the causal agent of late blight of potato Phytophthora infestans and the fungicide fenamidone, an imidazolinone recently introduced in the world market. The methodology included inoculation of leaf discs with a suspension of pathogens sporangia, evaluation of five doses of fungicide applied as active ingredient and commercial formulation, two techniques of application, statistical analysis using the Probit model and a molecular test based on sequencing the cytochrome b gene. This molecular test could be used both before or afterwards the biological evaluation, according to the availability of a supporting laboratory. We hope that this study can stimulate a continuous monitoring of the sensitivity level to QoI of populations of plant pathogens in Colombia.