Biological control of black scurf on potato under organic management

Field experiments showed that Trichoderma harzianum, nonpathogenic Rhizoctonia (np-R) and cattle manure compost amendment (CMC-H) applied in furrow could reduce black scurf incidence in organically grown potatoes. Incorporation of T. harzianum applied to the soil surface had a relatively small effect compared to the in-furrow treatment. Application of two isolates of nonpathogenicbinucleate Rhizoctonia (RS 521 and RU 56-8-AG-P) also significantly reduced the incidence of infected tubers in field experiments. Although treatments significantly reduced disease incidence and severity, total yield was unaffected. For the first time the efficiency of T. harzianum and np-R in reducing the incidence of black scurf on daughter tubers was demonstrated using naturally infested soil and contaminated seed tubers.