Detection and survival of Phytophthora ramorum in Rhododendron root balls and survival in rootless substrates

Sabine Werres, Annelies Vercauteren, Marko Riedel, Martine Maes, Kurt Heungens

    Research output: Chapter in Book/Report/Conference proceedingC3: Conference Abstract


    Rhododendron is an important host for the spread of Phytophthora ramorum. Disease symptoms can develop on the upper plant parts of Rhododendron growing in contaminated soil or growing substrate, but root symptoms have never been observed in naturally infected Rhododendron. Nevertheless, the pathogen has been isolated from asymptomatic Rhododendron roots. Latently-infected Rhododendron plants can therefore be an important source of inoculum for the spread of P. ramorum.
    The detection and survival of P. ramorum were studied in three experiments. In experiment 1, discs of infected leaf material were buried below the surface of either 1) various undisturbed soil columns or 2) a growing substrate for Rhododendron. The soils and the growing substrate were incubated for 33 months outdoors under quarantine conditions. Recoverability was assessed during several seasons. In experiment 2, artificially inoculated Rhododendron root balls were sampled over time using a new baiting technique. Roots were also examined for disease symptoms and for P. ramorum infection. In experiment 3, Rhododendron plants from a commercial nursery were cultivated for 25 months under quarantine conditions in a greenhouse. Outdoor temperatures were simulated. Symptom development was monitored and samples from the root balls were examined using various baiting tests.
    Long-term survival of P. ramorum could be demonstrated in all three experiments. The roots did not show any disease symptoms in spite of the infection detected.
    Original languageEnglish
    Title of host publicationFifth Sudden Oak Death Science Symposium - Meeting Abstracts
    Publication date2012
    Publication statusPublished - 2012
    EventFifth Sudden Oak Death Science Symposium - Petaluma, United States
    Duration: 19-Jun-201222-Jun-2012

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