Location: Horticultural Crops Research UnitTitle: Irrigation affects severity of root rot caused by Phythophthora plurivora and P. cinnamomi on rhododendron
Submitted to: Hortscience Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 5/12/2017
Publication Date: 9/19/2017
Citation: Scagel, C.F., Weiland, G.E., Grunwald, N.J., Davis, E.A., Beck, B.R., Mitchell, J.N. 2017. Irrigation affects severity of root rot caused by Phythophthora plurivora and P. cinnamomi on rhododendron. Abstract for American Society for Horticultural Science Annual Conference; Sept 19-22; Waikoloa, HI.
Technical Abstract: Plant pathogens in the genus Phytophthora cause root rot that decrease product quality and result in plant death and economic losses to the nursery industry. Recently, we found Phytophthora plurivora prevalent on rhododendron in nurseries in the Pacific Northwest, USA, but there is little information available to compare its pathogenicity in different environments to P. cinnamomi, a more well-studied rhododendron pathogen. Substrate moisture in container production can influence plant vigor as well as pathogen survival and inoculum build-up. We evaluated how irrigation frequency and volume affected the ability of P. plurivora and P. cinnamomi to cause disease on Rhododendron catawbiense ‘Boursault’ and ‘Roseum Elegans’. Plants were grown for 26 weeks in non-infested media (controls) or media infested with 1 propagule per gram (ppg) or 100 ppg of P. plurivora or P. cinnamomi. Our results indicate that (1) P. plurivora can cause similar losses in rhododendron plants as P. cinnamomi; (2) low substrate levels of Phytophthora can decrease plant health; (3) plants grown in media free of Phytophthora can adapt to a broader range of irrigation regimes than plants grown in infested media; and (4) irrigation management alters the incidence and severity of Phytophthora on rhododendron.