Effects of inhibitors of sclerotium formation on the sclerotial mycoparasite Coniothyrium minitans and its host Sclerotinia sclerotiorum

The formation of sclerotia is inhibited by certain chemicals. These resting fungal structures are also parasitized by mycoparasites. This study report s results of experiments on the effect of four sclerotial inhibitors on the sclerotial mycoparasite Coniothyrium minitans and was carried out in an at tempt to determine possible compatibilities between sclerotial inhibitors a nd mycoparasites. Thioglycolic acid was the most toxic to mycelial growth w hile its sodium salt was totally non-toxic. Mercaptoethanol and mercaptoeth ylamine were intermediate. At low concentrations, pycnidial formation by C. minitans was not hindered by any of the compounds tested. All four compoun ds inhibited the formation of sclerotia in Sclerotinia sclerotiorum. Sclero tia are also parasitized by C. minitans. Na-thioglycolate should be tested further as it had no adverse effect on the mycelial growth and pycnidium fo rmation in C. minitans, while it inhibited extensively the formation of scl erotia in S. sclerotiorum. These data suggest that Na-thioglycolate and C. minitans should be considered for use in integrated control.