First Report of Powdery Mildew Caused by Erysiphe aquilegiae on Columbine in the United States

Abstract

Columbine (Aquilegia sp., Ranunculaceae) is a late summer to fall flowering ornamental. Powdery mildew was collected from columbine plants growing outdoors in the botanical garden at the Center for Urban Horticulture, University of Washington (47.65°N; 122.29°W) in October 2016. Morphological characteristics of the fungus were consistent with those of Erysiphe aquilegiae. To confirm species identification, the internal transcribed (ITS) region of rDNA was amplified with the primers ITS4/ITS6. E. aquilegiae (LC009944) was the most similar species with eight nucleotide differences (98.6% similarity). Based on morphological and molecular characteristics, it was concluded that the powdery mildew fungus was E. aquilegiae. To the author’s knowledge, this is the first unequivocal report of E. aquilegiae occurring within the United States. These results are important for the U.S. floral industry, for which Aquilegia is a major crop.