Goal. To determine the species pathogens composition of sunflower diseases and to study the dynamics of development of the most harmful in the conditions of the western Forest-Steppe of Ukraine. Methods. The research was carried out during 2018—2019 in the research field of the Ukrainian Scientific Research Station on Plant Quarantine of Institute of Plant Protection using laboratory (pathogen identification) and field (examination of sunflower crops with sampling of plant material) methods. Results. Since the 1940s, the sunflower area in Ukraine has increased almost in 10 times: from 669 thousand hectares in 1939 to 5034 thousand hectares in 2017. The main crops — 75—80% are located in the steppe, and about 20% — in the Forest-Steppe zone. The sunflower crops are moving further to the west of Ukraine, where its areas increased in 2015—2017 by 1.7—6.4 times with large-scale climate change. However, the instability of weather conditions in this region and violations of the rules of agricultural technology lead to the defeat of sunflower plants by diseases of various etiologies. Researches studying the development of fungal diseases of sunflower have shown that the threat to crops was: embelizia (plant damage in the yellow basket phase was 73.3—100% with the development of the disease 36.7—75.5%); Alternaria (plant damage was 100% with the development of the disease 45—65.0%), verticillium wilt — the number of affected plants reached 35%, rust — for 100% of the affected plants, the intensity of sunflower damage was 3 points (for 5 score scale); the prevalence of phomosis and phomopsis for two years did not exceed 43.5%, and development — 15.4%. Conclusions. The most common during the study period (2018—2019) were: Alternaria alternata (Fr.Fr) Keissl.), embelizia (Alternaria helianthi Tub. et Nish.), verticillium wilt Verticillium albo-atrum Reinke et Berthold, V. dahliae Kleb., phomoses (Phoma oleraceae var. helianthi Sacc.) and phomopsis (Phomopsis helianthi Munt.Cvet. et al) in the western region of the Forest-Steppe of Ukraine.

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