Survival of Phytophthora ramorum in Tanoak and Rhodendron Leaves

I. McLaughlin, W. Sutton, E. Hansen, Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon, USA

Wild rhododendron and tanoak leaves inoculated with P. ramorum were placed in the field. Leaves were shaded or unshaded, and placed above ground or buried. Leaves were collected at intervals across two or three months. More than 90% of leaves were PCR positive. In the fall trial, 89% of buried leaves and less than 50% of surface leaves were culture positive for P. ramorum. In the summer trial, however, about 50% of buried leaves were culture positive and less than 5% of surface leaves were culture positive. Sporulation occurred on 32% of inoculated leaves that were culture positive.

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