Factors affecting biological control of Sclerotinia sclerotiorum by fungal antagonists

Studies were conducted to determine the effects of soil moisture (9, 16 or 24% w/w) and temperature (5, 15, 20 or 25 degrees C) on the control of sclerotia of Sclerotinia sclerotiorum by five fungal agents in sterile and natural field soil. All five biocontrol agents were effective in reducing the survival of sclerotia of S. sclerotiorum in sterile soil under dry (9% moisture) or wet (24% moisture) conditions at 20 degrees C, but only Coniothyrium minitans was effective in natural soil. Coniothyrium minitans was the most effective in reducing sclerotial viability at the temperature range of 15-25 degrees C. Trichoderma virens was effective against sclerotia of S. sclerotiorum to a lesser extent than C. minitans, and in non-autoclaved soil, it performed best at 25 degrees C. Although Epicoccum purpurascens, Talaromyces flavus and Trichothecium roseum were effective against sclerotia of S. sclerotiorum in some instances, they were less effective than C. minitans and T. virens. Sclerotia of S. sclerotiorum conditioned for myceliogenic germination were more vulnerable to attack by the biocontrol agents than dormant sclerotia. The implications are discussed with respect to enhancement of biological control of crop diseases caused by S. sclerotiorum in different geographic regions.