Phytophthora species Can Be Reliably Detected by Dogs Both From Infested Substrates and Infected Plants.

In recent years, reports of Phytophthora detections have increased from plant production facilities supplying plant stock for restoration projects (Garbelotto and others 2018). When introduced into new natural habitats through infected plant stock, the potential for Phytophthora infection and spread is high. Monitoring of nursery stock is key to reducing new introductions into wildlands, however, sampling in nurseries is currently considered too expensive and complex to be performed on a large scale. This study was undertaken to determine if it would be possible to train ecological scent detection dogs to discern Phytophthora species and discriminate Phytophthora odors from other scents in leaves and soil of infected plants. The U.C. Berkeley Forest Pathology and Mycology Lab teamed with H. T. Harvey & Associates to develop a Phytophthora detection dog pilot study (Swiecki and others 2018), starting with a single dog. The training has occurred in phases, first to expose the dog to recognize Phytophthora odor in a range of media. Four species of Phytophthora - P. ramorum, P, cinnamomi, P. nemorosa and P. cactorum - were grown in four different media - soil-water solution, soil-water-pea broth solution, local soil collected under oak trees, and commercial potting soil. The dog had a 100% detection level in blind testing consisting of 10 trials each. Phase two of the training employed infected Rhododendron plants for the scent trials. P. ramorum and P. nemorosa were inoculated on leaves, while P. cinnamomi and P. cactorum were soil inoculated. The dog again had a 100% detection success level in blind testing. In phase three, discrimination training of Phytophthora from co-occurring Pythium isolates was performed to ensure that the detection is genus specific. In addition, we tested the dog's ability to correctly identify Phytophthora infection in plant species other than Rhododendron spp. A fifth species of Phytophthora - P. tentaculata - was added to the dog's repertoire during this phase. The dog had 100% detection rate in double-blind testing consisting of 10 trials on the new Phytophthora species and very promising results during the Pythium discrimination trial. Results from the study so far suggest that ecological scent detection dogs may offer an innovative and reliable method to survey for Phytophthora in a variety of settings. Dogs could offer a rapid way to reliably detect the pathogen in a variety of controlled environments, such as nurseries; to prescreen plants before they are installed at habitat restoration sites; and possibly to identify infected naturally occurring plants and soil in the field. [ABSTRACT FROM AUTHOR]