Nowadays, phytopathogenic fungi cause the most serious yield loss in open field cultures, and sunflower (Helianthus annuus) is no exception to this phenomenon. Sclerotinia stalk and head rot (Sclerotinia sclerotiorum) is present in the whole area of Hungary, and can cause serious financial loss. In our experiment, sunflower hybrids were tested for resistance to Sclerotinia sclerotiorum infection. 16 sunflower hybrids were examined at the Experimental Breeding Site in Jászboldogháza. Pesticide treatment and also nutrient replacement were applied on the sunflower fields.