Biocontrol of sclerotinia diseases (Sclerotinia sclerotiorum) of sunflower and bean by Talaromyces flavus and Coniothyrium minitans

The effect of Talaromyces flavus and Coniothyrium minitans on Sclerotinia sclerotiorum, causal agent of sclerotinia wilt of sunflower and white mold of bean was examined. Laboratory investigations indicate that T. flavus is destructive to hyphae of S. sclerotiorum. Tips of hyphal branches invaded the host by direct penetration of the cell wall. Infection of host cells by T. flavus resulted in granulation of the cytoplasm and collapse of cell walls. Examination, using transmission electron microscopy, of sclerotinia inoculated with T. flavus indicated that T. flavus is also pathogenic to sclerotia of S. sclerotiorum. Hyphae of T. flavus penetrated the cell walls directly. Etching at the penetration site suggests that wall-lysing enzymes may be involved in the process of infection.;A four-year field study (1983-86) at Lethbridge and a three-year (1983-85) study at Winnipeg indicate that the incidence of sclerotinia wilt of sunflower and seed yield losses were reduced significantly with the application of T. flavus and C. minitans. In 1985, application of sclerotia but no hyperparasites to plots treated with both sclerotia and hyperparasite(s) in the previous two years resulted in low levels of disease in the T. flavus and C. minitans-treated plots (Lethbridge) and in the C. minitans-treated plots (Winnipeg). In 1986 (Lethbridge), the carry-over of biocontrol did not continue. Seed yield of sunflower was increased with the application of hyperparasites during 1984-85 and 1984 at the Lethbridge and Winnipeg sites, respectively.;A field study at Lethbridge (1984-85) showed that T. flavus and C. minitans reduced the carpogenic germination of sclerotia of S. sclerotiorum in a bean field. Coniothyrium minitans was more effective than T. flavus in both years.;In both sunflower and bean fields, the application of T. flavus and C. minitans affected the survival of sclerotia of S. sclerotiorum. Fewer sclerotia were recovered from the hyperparasite-treated plots and viability of the recovered sclerotia was reduced. The percentage of recovered sclerotia infected by T. flavus or C. minitans was low but concentrated in the hyper-parasite-treated plots.