Effect of crop rotation on the incidence of soil-borne fungal diseases of potato

Abstract

Effects of crop rotation on the incidence of soil-borne pathogens and on the performance of potato were investigated in five field experiments. Rotations differed in cropping frequency of potato and in crop sequence. Incidence of stem canker caused byRhizoctonia solani was strongly influenced by the cropping frequency of potato and not by crops with which the potato was alternated in the rotation. Cropping frequency of potato also affected the occurrence of black scurf, but less pronounced than for stem canker. The antagonistVerticillium bigutatum slightly reducedR. solani (black scurf) in plots on sandy soil continuously cropped with potato. Incidence of stem canker was also strongly affected by granular nematicides applied to the soil, nitrogen level and the cultivar grown. Stem infections byVerticillium dahliae depended on the cropping frequency of potato, by the crop with which the potato was alternated in the rotation and by the density and virulence of endoparasitic nematodes, especiallyMeloidogyne spp. Crop rotation had no effect at all on incidence of common scab on tubers, whereas the effect of cropping frequency of potato on netted scab was highly significant. When cultivars were grown susceptible to both scab types, netted scab supressed common scab.