Biocontrol of Sclerotinia sclerotiorum and Verticillium longisporum by the mycoparasite Microsphaeropsis ochracea

Abstract: Microsphaeropsis ochracea is a newly discovered mycoparasitic species of Coelomycetes that was first isolated in the 1990s from dead apple leaves originating from Canadian apple orchards (Bernier et al., 1996). By using M. ochracea in vitro and field experiments, it is possible to control Botrytis squamosa, Rhizoctonia solani and Venturia inaequalis (Carisse et al., 2000; 2001; 2006).The antagonistic effect of M. ochracea against the oilseed rape pathogens Sclerotinia sclerotiorum and Verticillium longisporum was investigated in laboratory and field experiments. In laboratory investigations we showed that the germination rates of sclerotia and microsclerotia were reduced by M. ochracea treatments. Decrease of germination strongly depended on M. ochracea inoculum density, the incubation temperature and the duration of incubation. In order to check the effect of M. ochracea on the two oilseed rape pathogens under field conditions we designed two long-term field experiments under an oilseed rape monoculture and an oilseed rape – winter wheat rotation. M. ochracea was applied as a formulated product (2,5 x 109 spores/g) in autumn before sowing and in spring before the start of stem extension at application rates of 1 kg/ha and 2 kg/ha.The results indicated lower infestations of rape plants with S. sclerotiorum in M. ochracea treated plots than in untreated plots.