Control ofRhizoctonia solani in potato by biological,chemical and integrated measures

Summary The effects of biological, chemical and integrated control on the formation of selerotia ofRhizoctonia solani on new potato tubers were studied in experimental fields. Sprouts of seed tubers, sprouted in daylight, were inoculated withVerticillium biguttatum, an ecologically obligate mycoparasite ofR. solani. Fungicides were mixed with the top soil. Biological control byV. biguttatum increased the percentage of harvests with less than 5% loss due to grading from 24% (non-inoculated) to 56%. Fungicides at the recommended rates usually gave good results but lower doses were less effective in sand than in loam soils. When fungicides were combined with biological control, the results were often, better: harvests with less than 5% sorting loss increased from 56 to 81%. Integrated control with pencycuron at 25% of the recommended rate was about equal to chemical control with pencycuron at full rate. The advantages of integrated control are discussed. Subsequently to the paper being provisionally accepted by the processing Editor, a shorter version of this paper was published in the Proceedings of the First Conference of the European Foundation for Plant Pathology, ‘Biotic Interactions and Soil-borne diseases’ held at Wageningen, 1990.