Evaluation of Risk of Resistance in Plant Pathogenous Fungi to Fungicides

Risk of resistance in plant pathogenous fungi to fungicides is composed of inher ent risk and management risk. At the beginning of the application of target fungicide, inherent risk of resistance can be predicted by artificial induct ion or fungicide selection, sensitivity variation of wild-type sensitive strain s, biological and genetic characteristics of resistant strains and mode of a ction of target fungicide. Several years after application of target fungicide, risk of resistance can be assessed according to the known experimental data, suc h as artificial induction or fungicide selection, efficacy appearance and resist ance occurrence in field, biological and genetic characteristics of resistan t strains, mode of action and application strategies of target fungicide. Curren tly, 4 methods have been adopted to evaluate risk of resistance. Inherent ri sk of resistance caused by diseases and fungicides can be divided into low, intermediate, and high level. High risk of resistance to phenylamide fungici des and lower risk of resistance to cymoxanil have been assessed in Phytopht hora infestans and Plasmopara viticola . Low or intermediate risk of resistan ce t o SBI has been forecasted in powdery mildew, rust, Fusarium spp. on whea t. Field resistance to high-risk fungicides can be delayed through suitable appl ication method, Unsuitable application of intermediate-risk fungicides may res ult resistance in field and outstanding decrease of control efficacy.