A new mycoparasite, Aspergillus sp. ASP-4, parasitizes the sclerotia of Sclerotinia sclerotiorum

A species of Aspergillus (strain ASP-4), belonging to the Aspergillus aculeatus clade of the black aspergilli, which can parasitize and destroy the sclerotia of the economically important plant pathogen Sclerotinia sclerotiorum was isolated from a field plot where oilseed rape had been planted for nearly 20 years. This is the first time that a member of Aspergillus section Nigri has been described as a mycoparasite. Inoculation experiments of S. sclerotiorum sclerotia were conducted in both the laboratory and field plots over a three year period. The results clearly show that the effect of this mycoparasite on reducing numbers of germinating sclerotia and subsequent spread of this pathogen is highly significant. Therefore, Aspergillus sp. ASP-4 has the potential to be an important biocontrol agent. In addition, since Aspergillus sp. ASP-4 infects sclerotia, the application time and method for the prevention and control of Sclerotinia stem rot of oilseed rape can be made relatively easy compared to the critical timing of fungicide application during the early to mid-flowering season, as fungal spores can be sprayed directly on to soils after oilseed rape harvest.