S. Swain and M.M. Garbelotto. California Agriculture 69(4):237-241. DOI: 10.3733/ca.v069n04p237. October-December 2015.
Phytophthora ramorum, the causal agent of the disease sudden oak death has killed millions of trees on the north coast of California. An introduced pathogen both in North America and Europe, it was discovered in California in 1995. P. ramorum often forms lethal bark lesions on oaks (Quercus spp.) and the related tanoak (Notholithocarpus densiflorus), but it spreads by spores formed on foliar lesions on scores of other plant species, including common landscape plants. New foliar hosts have been discovered annually since 2002, and the symptoms can vary substantially from host to host. The disease keeps spreading to new locations through limited-distance natural dispersal, infected nursery stock and perhaps through other yet unknown means To help prevent the spread of the pathogen to new localities, movement of infected plant material is highly regulated. Debris from infected plants is almost certainly taken to local composting facilities, which are subject to restrictions on shipping product out of the quarantine area if found to be not pathogen-free. Finished compost has a well-established history of suppressing a variety of plant pathogens when incorporated into potting mixes or planted into soil. The survival of P. ramorum in finished compost, however, had not previously been evaluated. The purpose of this research was to address the question of whether P. ramorum may have a high survival rate in finished compost if reached by dispersal propagules that may be transported by wind or water from fresh green waste or infectious plants within or near composting facilities.
The results show that P. ramorum may be present and infectious if introduced into finished compost, and that variations in compost characteristics appear to influence survival rates.
For the complete article see: https://ucanr.edu/repositoryfiles/cav6904p237-159798.pdf