Interference by common leaf saprophytic fungi with the development of Phoma betae lesions on sugarbeet leaves

SUMMARY When sugarbeet leaves were inoculated simultaneously with the parasitic Phoma betae and the saprophytic Aureobasidium pullulans or Torulopsis Candida, the development of expanding lesions caused by P. betae was curtailed. Two other common saprophytes, Sporobolomyces pararoseus and Cladosporium cladosporioides, also decreased numbers and sizes of expanding lesions in the presence of pollen. The numbers of saprophyte cells applied to inoculum areas were similar to those occurring naturally on sugarbeet leaves in the summer. Lesion development was not affected by a mixture of heat‐killed cells of the four saprophytes.