Crops that decrease the survival rate of sclerotia of Sclerotium cepivorum Berkeley in their root systems and attenuate the progress of white rot disease

We examined the influences of cultivation of several crops on sclerotia of the allium white rot pathogen, Sclerotium cepivorum Berkeley. The survival rate of sclerotia that were buried in the root systems of soybean, bell pepper, or corn (maize) was significantly less than that of sclerotia in soil that was left fallow. Although soils in which bell pepper, sweet potato, and corn had been grown attenuated the progress of white rot disease, the filter-sterilized exudate of these soils did not affect hyphal growth or the virulence of sclerotia. These results indicate the existence of unknown factors that attenuate white rot disease through crop rotations other than soil physiochemical properties. The combination of prior corn cultivation followed by pre-planting irrigation with fungicide for Welsh onion seedlings gave a significantly higher disease protection rate than either practice alone. These results support the promotion of crop rotation for labor-saving crop protection against white rot disease.