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Research Project: Integrated Water and Nutrient Management Systems for Sustainable and High-Quality Production of Temperate Fruit and Nursery Crops

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Title: Comparing methods for inducing root rot of Rhododendron with Phytophthora cinnamomi and P. plurivora

item MESTAS, ANGELA - Oregon State University
item Weiland, Jerry
item Beck, Bryan
item Davis, Elizabeth
item Grunwald, Niklaus - Nik
item Scagel, Carolyn

Submitted to: Phytopathology Supplement; APSnet (Plant Pathology Online)
Publication Type: Abstract Only
Publication Acceptance Date: 9/28/2017
Publication Date: 12/1/2017
Citation: Mestas, A., Weiland, G.E., Beck, B.R., Davis, E.A., Grunwald, N.J., Scagel, C.F. 2017. Comparing methods for inducing root rot of Rhododendron with Phytophthora cinnamomi and P. plurivora [abstract]. Phytopathology. 107:S5.189.

Interpretive Summary:

Technical Abstract: Root rot, caused by Phytophthora cinnamomi and P. plurivora in containerized Rhododendron, can cause significant losses in the nursery industry. Studies commonly use a 48 h flooding event to stimulate root infection. While flooding rarely occurs in container nurseries, plants may sit in a shallow puddle of water when irrigated too frequently and drainage is poor. Nursery transplant practices can damage roots and may predispose plants to more rapid disease progression. A greenhouse study was conducted comparing disease development on 1.5-year-old R. 'Boule de Neige' plants inoculated with P. cinnamomi or P. plurivora, then either flooded (48 h, then maintained at container capacity) or placed in a saucer kept permanently full of water. The effect of low vs. high transplant damage was also evaluated. The experiment was a full factorial RCBD with 10 replicates of each treatment. Plants were evaluated weekly for symptom development. Regardless of water or damage treatment, plants inoculated with P. cinnamomi were more chlorotic and had a greater number of wilted and dead plants by week 12 than noninoculated controls or plants inoculated with P. plurivora. Noninoculated and P. plurivora-inoculated plants were similar, with few symptoms of chlorosis or wilt, and no dead plants. Results suggest that both methods of inducing high substrate moisture (flooding vs. saucer) are effective for inducing root rot symptoms in plants inoculated with P. cinnamomi.