5-Aryloxy-5-azolyl-3,3-dimethylpent-1-en-4-ones and -ols of the formula ##STR1## in which Ar is an optionally substituted aryl group,Az is a 1,2,4-triazol-1-yl, 1,2,4-triazol-4-yl or imidazol-1-yl group, andB is a keto group of a CH(OH) grouping,or addition products thereof with physiologically acceptable acids or metal salts are suitable for use as plant protection agents, and can be employed with particularly good success for combating those fungi which cause powdery mildew diseases, thus for combating Erysiphe species, Sphaerotheca species and Podosphaera species, and for combating diseases of rice.