The application relates to the methods for preventing, treating, or reducing an infection by phytopathogenic, facultative saprophytic or saprotrophic microbes (e.g. phytopathogenic fungi) in crop plants (pre-harvest), or in a crop plant material, or on surfaces in contact with the crop plant material, comprising: contacting them with a composition containing nootkatone and optionally an additional active ingredient; or comprising applying said composition to a vector pest. The application further relates to the compositions comprising nootkatone and optionally an additional active ingredient.