S.A. Tjosvold1, D.L. Chambers2, J.M. Davidson3, and D.M. Rizzo3
Phytophthora ramorum, the causal agent of the disease commonly known as Sudden Oak Death is a prevalent pathogen in California with its effects evident in 12 counties and found on 14 different oak, tanoak and non-oak hosts. The disease has been commonly found in areas of high recreational use such as state parks and forest service lands. In some of the most heavily diseased areas, recreational hikers frequent the trail systems. It is important to understand if the pathogen inoculum is found in soil along the hiking trails and, if inoculum is there, whether it could be picked up on shoes of recreational hikers. The spread of inoculum could then be a real threat as the hiker visits new areas.
Sampling occurred following rainy periods in March and May and then monthly through the dry summer and fall period 2002 in a popular California State Park. At each sampling date, soil was sampled from five locations along a 1.3 km "nature trail" loop and from the bottom of shoes of hikers who had hiked the trail. In the laboratory, soil samples were baited with pears, inspected for characteristic P. ramorum lesions, and pear tissue from suspicious lesions were transferred to PARP media for pathogen identification.
In the spring rainy periods, the incidence of successful pear baiting for P. ramorum varied from 40 - 60 % success rate for trail soil and 40 - 95% success rate for soil removed from hiker’s shoes. In the dry summer period, no baiting was successful from trail soil or shoe soil.
