Impact of seed sowing rate on disease occurrence on sunflower in the Krasnodar region

In 2021-2022, we studied the dependence between sunflower hybrid plants infection (Status, Aurus, Tyzar, Klip, and Surus) with different diseases and seed sowing (40, 60, and 80 thousand seeds/hа). Disease prevalence on plants of the studied sunflower hybrids was as following: root rot - 28%, Alternaria blight - 14-20, dry rot - 11-18, Phomopsis - 0-2, Phoma rot - 2-15%. Environmental conditions influenced a lot the plants infection with pathogen and their occurrence. Thus, in 2021, the crops were infected weakly with Phomopsis (Phomopsis helianthi Munt.), Phoma rot (Phoma macdonaldii Boerema), and rust (Puccinia helianthi Schw.) - within 1-2%, and in 2022, Phoma rot and rust - 15-16%. At a sowing rate of 40 thousand seeds/ha, sunflower plants infection with Phoma rot, dry rot, and bacterial disease raises, and at thickening up to 80 thousand seeds/ha, the plants infection with charcoal rot, rust, and alternaria blight increases. Depending the research year, there was noted a weak infection of hybrids Aurus, Tyzar, and Status with fusarium wilt and rust, Tyzar and Aurus - with bacterial disease, Aurus - with dry rot and alternaria blight.