Cause The fungus Erysiphe diffusa (formerly Microsphaera diffusa) has been reported from Oregon, Washington and Idaho while Podosphaera clandestine has been reported from Washington and Idaho.
Symptoms White to gray powdery growth on the surface of leaves. Leaves may be deformed if infected when not fully expanded.
Control There are no reports about the control of this disease and there seem to be no fungicides specifically registered for this crop.
Reference Braun, U. and Cook, R.T.A. 2012. Taxonomic Manual of the Erysiphales (Powdery Mildews). CBS-KNAW Fungal Biodiversity Center, The Netherlands.