Abstract: The Czech Republic is one of the European leaders in reducing pesticides in
agriculture. The narrow selection of active substances as well as the demand of retail chains for the least chemically loaded fruit is thus a great obstacle for fruit growers. We tested two
treatment systems against apple scab and powdery mildew. In the first system we tested copper and sulfur fungicides applied in combination with alternative products of two companies (alternatives: in trial 1 – potassium bicarbonate, earthworm compost extract; in trial 2 – plant defense stimulator based on plant extracts and oils, boretalonamine, soy lecithin and sunflower oil, potassium fertilizer, chitosan hydrochlorid) on apple cv. Idared. Efficacy against powdery mildew was 22-63 %, against scab on leaves 80-91 %, and against scab on fruit 74-96 %. In the second system we tested only alternative products (copper and zinc-based fertilizer, potassium fertilizer, chitosan hydrochlorid, zinc and chitosan hydrochlorid based biostimulant) without copper and sulphur fungicides on apple cvs. Rubinola, Melrose and Gala. The highest efficacy was achieved by the scab resistant cv. Rubinola, i. e., 65 % against scab on leaves and 75 % on fruits. The efficacy for the sensitive cvs. Gala and Melrose was 44-49 % against scab on the leaves whereas, only 26-30 % on the fruits.