Sudden oak death (SOD) is caused by Phytophthora ramorum, an exotic pathogen introduced multiple times in California, Oregon and Washington. The pathogen has been spreading in California and Oregon forests at relatively modest rates from the initial introduction points, covering mostly distances in the range of hundreds of meters, and only occasionally spreading 3-5 km away from established infestations. In California, oak (Quercus spp.) and tanoak (Notholithocarpus densiflorus) are infected only when infected California bay laurel (Umbellularia californica) trees are within tens of meters, hence, a fine-scale knowledge of infected bays is important to assess the risk for oak infection at any given location. Since 2008, the University of California-Berkeley Forest Pathology Laboratory has been enlisting and training volunteers to survey woodlands for the presence of SOD. Symptomatic leaves are collected by volunteers and tested at U.C. Berkeley. Since 2012, results of these citizen-science efforts have been combined with results of surveys by researchers and government agencies and displayed jointly in the web-based SODmap. In 2013, a mobile app was launched to view SOD distribution in the field and to determine the risk for oak infection at any given location. This is one of the first large-scale joint efforts between volunteers, government agencies and academia resulting in valuable management tools for a forest disease.
