The effect of crop year (2018 and 2019) and agrotechnical factors (sowing date, crop density, fungicide treatment) was observed on the leaf, stem and head diseases of the sunflower hybrid ES Loris, as well as its stem rigidity and yield on calcareous chernozem soil in the Látókép Experiment Site (47°33’, 21°27’) located in the Hajdúság region of Hungary. The obtained findings showed that the extent of Alternaria, head disease, Phoma, Sclerotinia and Diaporthe infections was reduced by the late sowing date and the applied fungicide treatment, while higher crop density increased infection. In 2018, the yield of ES Loris was between 3607–4977 kg ha-1, while it ranged between 3204–4795 kg ha-1 in 2019. In 2018, early sowing (early April) proved to be optimal, while late sowing (early June) showed better results in 2019. Due to the high level of infection and lodging, lower crop density (35–55 thousand plants per ha) provided the highest yield in both years. As a result of fungicide treatment, the yield surplus obtained in comparison with the control treatment ranged between 150–600 kg ha-1 in 2018 and 350–500 kg ha-1 in 2019. Under the given ecological and agrotechnical circumstances, the highest impact on the yield of ES Loris was observed in the case of the fungicide treatment (43%) and crop density (31%).

Keywords: sunflower, sowing date, fungicide, crop density, diseases, yield