Monitoring of Phytophthora ramorum in the north central United States

Frances S. Ockels and Pierluigi Bonello, Dept. of Plant Pathology, The Ohio State University, Columbus, OH 43201; 216-688-5409; ockels.1@osu.edu; Manfred Mielke, USDA Forest Service, St. Paul, MN 55108

Participating in the 2004 US Forest Service SOD monitoring program, our lab surveyed nursery perimeters and forest sites and processed samples from Ohio, Indiana, Illinois, Missouri, Iowa, and Wisconsin. As part of the USFS protocols, samples were stored in an ice chest on sealed coolant and shipped to lab for P. ramorum detection within 72 hours of collection using PCR-based procedures. Results showed that 89 samples from Ohio, 100 samples from Indiana, 75 samples from Iowa, 75 samples from Missouri, and 219 samples from Wisconsin were free of the pathogen. During surveys, the process of storing the samples on coolant and shipping every two days became cumbersome in terms of expense and convenience. Thus, we explored the feasibility of desiccating the samples as a way of preserving tissues at ambient temperature. Symptomatic leaves were placed in a plastic bag in the presence of a sachet containing Drierite. Fungal DNA extracted from Drierite-desiccated samples was successfully amplified by PCR using universal ITS primers. However, further work is needed to show that P. ramorum infected leaves can be desiccated and still allow for PCR-amplification of P. ramorum DNA. Currently, our lab is not permitted to work with P. ramorum infected material.

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