Submitted to: Plant Health Progress
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/3/2005
Publication Date: 11/22/2005
Citation: Hartney, S., Glawe, D.A., Dugan, F.M., Ammirati, J. 2005. First report of powdery mildew on corylus avellana caused by phyllactinia guttata in washington state. Plant Health Progress. doi:10.1094/PHP-2005-1121-01-BR. Interpretive Summary: Phyllactinia guttata is a powder mildew fungus which grows parasitically on a wide range of deciduous trees and a smaller number of herbaceous hosts. It has previously been reported on several cultivars of hazelnut (Corylus species) in the Pacific Northwest and elsewhere, and was previously reported on European hazelnut (C. avellana) in Oregon. This is the first report of P. guttata on European hazelnut in Washington State. The fungus was found in 2004 on C. avellana variety contorta (contorted hazelnut) in Pullman, Washington, and also on C. avellana (variety unknown) in Seattle, Washington. In each instance, damage to the host was minimal.
Technical Abstract: Contorted hazelnut (Corylus avellana variety contorata) is an ornamental tree introduced to North America from Europe. In the fall of 2004, powdery mildew caused by Phyllactinia guttata was observed on contorted hazelnut located on the campus of Washington State University, Pullman, Whitman Co. Powdery mildew also was observed on several C. avellana trees (European hazelnut, unknown cultivar) on the campus of the University of Washington, Seattle, King Co. There are previous reports of P. guttata occurring on C. avellana in Europe, Iran, and Canada but within the US P. guttata has been reported on this host only in Oregon. This report documents for the first time the occurrence of P. guttata on C. avellana in both eastern and western Washington. Signs of the disease included white mycelial growth and accompanying chasmothecia on abaxial leaf surfaces. Symptoms included production of chlorotic areas on adaxial leaf surfaces. Chasmothecia, asci and ascospores matched standard descriptions for the species. Several conidia resembling those reported for this species were observed but were in poor condition. Voucher specimens were deposited with the Mycological Herbarium (WSP) of the Plant Pathology Department at Washington State University. Phyllactinia guttata attacks a very broad range of deciduous trees and a smaller number of other plants.