The fungal mycoparasite Coniothyrium minitans infects and kills the sclerotia (survival structures) of the fungus that causes white mold (Sclerotinia sclerotiorum). This commercially available fungus can be sprayed on crops infested with white mold to reduce contamination of soil with sclerotia, lowering the risk of disease in subsequent crops.
Sclerotial survival was monitored for seven years, during 5 years of experimentation and during two subsequent years, when the field was returned to commercial agriculture. Potato, bean, carrot, and chicory, which are all susceptible to S. sclerotiorum, were grown in rotation. Crops were rotated in each plot, but treatments of C. minitans, Trichoderma spp. or no treatment were applied to the same plot every year. The Trichoderma treatment was replaced by a single spray with C. minitans during the fourth and fifth years of the trial, since it showed no effect on sclerotial survival during the first 3 years. The effect of treatments was monitored in the two subsequent seasons by counting apothecia (fungal fruiting structures) as a measure of surviving white mold sclerotia and scoring disease incidence.
C. minitans infected at least 90% of white mold sclerotia on treated crops by the end of the each season. The fungus also reduced the number of apothecia compared with the other treatments during the second year after the bean crop. During the fifth year of the trial, C. minitans reduced the number of apothecia by nearly 90% and reduced disease incidence in the bean crop by 50%, resulting in a slightly higher yield.
The final population size of sclerotia in soil at the end of the 7-year period was lower in all C. minitans plots than at the beginning of the trial, even in plots where two highly susceptible bean crops were grown during the period. This indicates that the mycoparasite C. minitans can keep contamination of soil with sclerotia low even in crop rotations that include several crops susceptible to white mold.
Gerlagh, M., H. M. Goossen-van de Geijn, N. J. Fokkema, and P. F. G. Vereijken. 1999. Long-term biosanitation by application of Coniothyrium minitans on Sclerotinia sclerotiorum infected crops. Phytopathol. 89(2):141-147.
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