The decrease in soybean rust control using fungicide mixtures (DMAs+QoIs) reached very low levels for the harvest of 2012/13 (an average of 37% for the three main mixtures). This decrease is due to a decrease in Pp sensitivity to individual DMIs and QoIs, and mixtures thereof. Anti-resistance strategies have not been introduced in Brazil for preventing/delaying the development of resistance of the fungus that is the casual agent of rust (Phakopsora pachyrhizi) in soybean [plant form the family Fabaceae, Glycine max (L.) Merr.] and of the fungus that is the casual agent of yellow leaf spot (Drechslera tritici-repentis) in wheat [plant of the family Triticea, Triticum aestivum L.], as well as other disease complexes that attack the main crop plants in Brazil, such as corn, beans, cotton, inter alia. By means of said method it is possible to recover the efficiency of several mixtures (DMI+QoI and QoI+SDHI) due to a decrease in fungal sensitivity. The methods described by the present invention seek to increase the effective useful life of fungicides and increase grain yield.