Abstract
Sixteen isolates of Pezicula alba Guthr. were examined. The intensity of growth on various media, pathogenicity to apple fruits and twigs, colour of cultures and size of conidia were measured. Some isolates are pathogenic to fruits, some others to twigs; one isolate (only no. 19) is pathogenic to both twigs and fruits; many isolates are not - pathogenic at all. Culture growth, sporulation and size of conidia are not correlated with the pathogenicity of the isolate. The mean size of conidia is 21.29µm x 3.48µm.