Walfiporia dilatohypha, previously known from eastern North America on
ly, is reported from Arizona on fallen silverleaf oak. Distinctive cul
tural characters include lack of clamps, profuse development of arthro
spores and chlamydospores, and negative oxidase reactions. Agar block
decay tests with silverleaf oak and white fir test blocks resulted in
little change in weight or appearance of the blocks.