Zonal pathogen complex of sunflower in the left bank Forest-Steppe of Ukraine

Abstract

Aim. To determine a set of sunfl ower pathogens and their variability infl uenced by hydrothermal conditions of the crop growing season. Methods. Over the period of 2007–2016, due to phytosanitary monitoring of breeding crops of the scientifi c crop rotation of the Plant Production Institute named after V.Ya. Yuriev of NAAS, the prevalence degree, development intensity and variability of sunfl ower diseases in the Eastern Forest-Steppe of Ukraine were estimated. The hydrothermal coeffi cient (HTC) is presented for the sunfl ower growing season and by developmental phases of the crop. Results. Phomopsis blight (Phomopsis/Diaporthe helianthi Munt.- Cvet. et al.), gray mold (Botrytis cinerea Pers.), dry rot (Rhizopus sp.), charcoal rot (Sclerotium bataticolaTaub), and downy mildew (Plasmopara helianthi Novot. f. helianthi) were the most common diseases on sunfl ower in the Eastern Forest-Steppe of Ukraine in 2007–2016. The weather conditions of 2007–2016 considerably varied and were characterized by fl uctuations in the hydrothermal coeffi cient (HTC) from 0.57 in 2009 to 1.1 in 2014. Assessing the incidence of the fi ve most common and harmful sunfl ower diseases (dry rot, charcoal rot, gray mold, Phomopsis blight, downy mildew) by cluster analysis for the ten-year study period in relation to the weather conditions of a year, we found that both dry and charcoal rots were co-associated with aridity, while downy mildew and gray mold were frequently promoted by waterlogging during a certain period of sunfl ower development. Unlike the other diseases, Phomopsis blight, being an annual disease, appears to have no clear dependence on any specifi c conditions. Conclusions. Based on the phytosanitary monitoring results of crops in the Eastern Forest-Steppe of Ukraine, the sunfl ower phytopathogen complex composition was determined. The prevalence degrees for Phomopsis blight, gray mold, dry rot, charcoal rot, and downy mildew as well as the development intensities of Phomopsis and gray mold were established. The co-incidence of the fi ve most harmful sunfl ower diseases in the Eastern Forest-Steppe of Ukraine (dry rot, charcoal rot, gray mold, Phomopsis blight, downy mildew) was evaluated during the ten-year study period, depending on the weather conditions of a year.