Virginia mallow is a plant from the central and eastern states of North America. A large amount of high quality biomass obtained from V. mallow led to interest in this plant for bioenergy purposes. Unfortunately, high incidence of white rot disease caused by Sclerotinia sclerotiorum destroyed plantations of this plant. In previous attempts, various control strategies were not successful and all treatments failed (including the use of Coniothurium minitans). The aim of the study was to find and evaluate yeast-like fungi for biocontrol of S. sclerotiorum, evaluate the optimal thermal condition for biocontrol efficacy, and describe possible modes of action of potential biocontrol organisms. In dual bioassay test with 19 strains of yeast-like fungi with S. sclerotiorum, antagonistic potential were obtained. At different temperatures variations in antagonistic activity of yeast-like fungi were observed. At all tested temperatures (i.e., 4, 12, and 23°C), positive results were obtained. Extracellular enzymes were produced by the majority of antagonistic yeast, such as: amylases (the most frequent), chitinases, proteases, pectinases and xylanases. In this research, reduction in white rot symptoms on V. mallow stems was significant (P < 0.05). The highest inhibition of disease was observed after treatment with strains (114/64) Candida albidus and (117/10) Pichia anomala.