Suppressive effects of soils against sugar beet damping-off diseases induced by a fixed period of time after incorporation of dried crop residues

Abstract

The suppressive effects of soils amended with dried crop residues against damping-off of sugar beet and colonization of the pericarp by Rhizoctonia solani and Pythium ultimum were evaluated in a field soil infested with either or both pathogens. Pericarp colonization and damping-off by R. solani were both significantly suppressed when the pasteurized, pathogen-infested soil was amended with dried residue of komatsuna or peanut immediately before sowing and incubated at 22-17 ℃. However, the same soil treatment suppressed neither the saprophytic nor the pathogenic activities of P. ultimum. The same trends were observed when seeded soils were incubated at 32-27 ℃. Likewise, neither plant residue suppressed the disease when incorporated into non-pasteurized infested soil. High incidences of damping-off were also observed in non-infested field soil without residues. In contrast, damping-off was significantly suppressed when the non-pasteurized field soil amended with either residue was incubated at 22-17 ℃ or 32-27 ℃ for 25 days prior to sowing. These results indicated that dried residues of komatsuna and peanut plants could be an agent to induce soil suppressiveness against both pathogens, although induction of disease suppression was observed after a fixed period following post residue amendment in non-pasteurized soil.