Studies on sensitivity of microorganisms colonizing the leaves of winter wheat cultivar Almari to Amistar 250SC, Bravo 500SC fungicides and Bion 50WG plant resistance stimulator were performed in 2000-01. The studied fungicides decreased growth of hyphae fungi colonizing the leaves of winter wheat cultivated in pots, especially 24 hours after treatment, compared to control. Created free ecological niche was inhabited by bacteria and yeast-like fungi. From leaves treatment with Bion 50WG, the number of isolated microorganisms was bigger than control. In vitro fungicides Bravo 500SC and Amistar 250SC were very toxic to fungi Rhodotorula sp., Saccharomyces sp. and Cryptococcus sp. Colonizing the leaves of winter wheat. Bion 50WG plan resistance stimulator was toxic, but only in concentrations of 50 and 500 µg to Rhodotorula sp. Studied plant protection agents stimulated of strain Candida albicans.