The population of oomycete Plasmopara halstedii (Farl.) Berl. et de Toni (sunflower downy mildew pathogen) has been monitored in Krasnodar and Rostov regions and the Republic of Adygea for more than 15 years. Prior to the beginning of the 2000s there were races 100 300 310 and 330 in the regions. In the period from 2004 to 2007 races 100 300 310 and 700 were recorded sporadically. The race 330 was the most common; in a number of agrocoenoses it was 100 % of samples. In some fields races 710 and 730 prevailed. In 2008'2011 only races 330 710 and 730 were found; the race 330 have been still prevailed and was also found on Ambrosia artemisiifolia L. Since 2012 in the majority of fields races 710 and 730 prevailed and the race 330 wasn't allocated in many of them; for the first time in Russia pathotype 334 that able to overcome Pl 6 was found in Krasnodar region. In the period of 2013'2015 increased distribution of the race 334 in the Krasnodar region and the Republic of Adygea was observed. At the same time in 2014 in one field in the Rostov region only races 310 and 330 (prevailed) were identified. The virulence of the pathogen population is closely connected with the cultivated assortment of sunflower. Further spread and accumulation of P . halstedii race 334 and the emergence of new pathogen pathotypes in the said regions are predicted.