Osjetljivost suncokreta na biotski stres uvelike određuje vrijednosti agronomskih svojstava. Uzročnici biotskog stresa mogu biti različiti, a u svijetu pa tako i u Hrvatskoj se po svome utjecaju izdvajaju bolesti. Uslijed pojave različitih biljnih bolesti, u pojedinim godinama prinosi zrna i ulja suncokreta mogu biti reducirani i preko 50%. Najčešći uzročnici bolesti suncokreta su gljive, a prema stupnju štete koje prave ističu se Sclerotinia sclerotiorum, Diaporthe/Phomopsis helianthi i Plasmopara halstedii te u nešto manjoj mjeri Alternaria helianthi, Phoma macdonaldii, Puccinia helianthi, Verticillium spp., Botrytis cinerea, Macrophomina phaseolina i Erysiphe cichoracearum. Kreiranje otpornih/tolerantnih linija iz divljih formi suncokreta, a zatim transfer poželjnih gena u komercijalne linije i hibride je najčešći oblik povećanja otpornosti/tolerantnosti linija i hibrida suncokreta na biotski stres. U ovom postupku značajnu ulogu ima primjena molekularnih markera. Pored toga važan je stalni monitoring, ali i pravovremena primjena agrotehničkih, kemijskih i bioloških mjera.; The sensitivity of sunflower to biotic stress largely determines the values of its agronomic traits. In Croatia, as well as in the world, the causes of biotic stress can be different so diseases regulary appear due to their influence. Sunflower grain and oil yield can be reduced over 50% in some seasons accordingly. The most common causes of sunflower disease are fungi. According to the extent of damage they cause - Sclerotinia sclerotiorum, Diaporthe /Phomopsis helianthi and Plasmopara halstedii belong to major causers, whereas infestation with Alternaria helianthi, Phoma macdonaldii, Puccinia helianthi, Verticillium spp., Botrytis cinerea, Macrophomina phaseolina and Erysiphe cichoracearum keep a lower extent. Developing resistant/ tolerant lines from wild forms of sunflower and then transferring desirable genes to commercial lines and hybrids are the most common form of increasing the resistance/tolerance of sunflower lines and hybrids to biotic stress. The use of molecular markers plays a significant role in this process. In addition, constant monitoring is of the utmost importance as well as timely application of agrotechnical, chemical and biological measures.