Notes on powdery mildews (Erysiphales) in Japan: I. Erysiphe sect. Erysiphe

• Powdery mildews belonging to Erysiphe sect. Erysiphe were described.
• Eight host species were reported as new hosts in Japan.
• First morphological and molecular data were presented for two Erysiphe species.

Erysiphe aquilegiae on Thalictrum tuberiferum and Trollius hondoensis, E. cf. aquilegiae on Aconitum grossedentatum, E. huayinensis on Isodon umbrosus var. excisinflexus, E. liriodendri on Liriodendron tulipifera, E. mayorii var. japonica on Cirsium shinanense and Ci. nipponicum var. incomptum, E. sedi on Sedum bulbiferum, E. trifoliorum on Trifolium dubium, and Pseudoidium cf. neolycopersici on Corchoropsis tomentosa are described and illustrated. Of the host species listed, eight, viz. Th. tuberiferum, Tro. hondoensis, A. grossedentatum, I. umbrosus var. excisinflexus, Ci. shinanense, Ci. nipponicum var. incomptum, Tri. dubium, and Co. tomentosa, are new hosts of powdery mildews in Japan.