The evolution of virulence in UK oat powdery mildew (Blumeria graminis f.sp
. avenae) populations is presented along with comparative information on th
e deployment of resistant cultivars. Virulence frequencies have followed cl
assical gene-for-gene principles, and there are no effective resistance gen
es currently deployed in cultivars grown in the UK. The incidence of powder
y mildew in continental Europe and pathogen variation is reviewed as well a
s other strategies for the control of this disease. New resistant sources h
ave been identified and are being used in breeding programmes throughout Eu
rope.