USDA Forest Service

Pacific Southwest Research Station
Pacific Southwest
Research Station

800 Buchanan Street
Albany, CA 94710-0011
(510) 883-8830
United States Department of Agriculture Forest Service. USDA logo which links to the department's national site. Forest Service logo which links to the agency's national site.

Research Topics: Insects and Disease

Main Topic | White Pine Blister Rust | Pitch Canker | Sudden Oak Death | Invasive Insects

Sudden Oak Death (Phytophthora ramorum)

Photo courtesy USDA Forest Service, Forest Health Protection

Since the mid-1990s, Phytophthora ramorum, the exotic plant pathogen that causes Sudden Oak Death, has killed millions of oak and tanoak trees, and millions more are infected in 14 coastal California counties and one county in southwestern Oregon. Phytophthora ramorum also causes a leaf or twig blight on over 125 plant species, including popular ornamental plants, such as rhododendrons and camellias. With many of these popular ornamental host plants being shipped nationally and internationally, there is concern over inadvertent pathogen transport and introduction. In the United States, European Union, Canada and over 60 other countries, federal and state quarantines are in effect to prevent pathogen hitch-hiking on plant materials.

The USDA-FS, Pacific Southwest Research Station (PSW) Sudden Oak Death/Phytophthora ramorum research program began in December 2002, with support from the Washington Office, and funding from Congress, for a national research program to address the emerging threat of sudden oak death. The research program has aggressively investigated key issues associated with this quarantine pathogen, providing findings to support decision-making by land managers, arborists, homeowners, regulators, nurserymen, policy makers, and others.

Because this quarantine pathogen was new to science, most research was initially conducted in California, where the disease occurred in the natural environment. The PSW adopted a peer-reviewed, grant-based approach to provide a nimble mechanism by which the program direction could evolve as researchers answered early questions and new ones arose. Over the past decade, more than $11.5 million in research has been supported (including some funds provided by the state of California). Approximately 40 agreements are currently in place at 20 organizations in eight states, the UK, and Germany.

Goals and objectives. The USDA-FS, PSW SOD Research Program is an applied research program aimed at serving the needs of stakeholders impacted by P. ramorum, and organizations and individuals seeking to protect natural, economic, and social resources by prevention of the pathogen's introduction or establishment. Additionally, the program aims to prevent the initiation of new damaging biological invasions by elucidating the lessons learned from this epidemic and by evaluating the risks of Phytophthoras to US forests, communities, and industries

These goals are being fulfilled through the following objectives:

  1. Develop methods and strategies to prevent, treat, manage, and mitigate the impacts of P. ramorum, and respond to the hazards it creates;
  2. Improve early detection and monitoring methods for SOD and related diseases; and
  3. Elucidate the ecological, economic, and social impacts of P. ramorum and other forest Phytophthora species.

Sudden Oak Death Science Symposia

The Proceedings of the Sudden Oak Death Fifth Science Symposium has been published in two volumes:

  • Frankel, S.J.; Kliejunas, J.T.; Palmieri, K.M.; Alexander, J.M. tech. coords. 2013. Proceedings of the Sudden Oak Death Fifth Science Symposium. Gen. Tech. Rep. PSW-GTR-243. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. 169 p.
  • Frankel, S.F. (ed). 2013. Tanoak: History, Ecology and Values. Madroño 60(2): 62-164. Articles found on pages 63, 87-94, 107-117, 130-138, 139-50, and 151-164 are available in Treesearch. *Due to policy or copyright restrictions, we are unable to provide a full-text version of this publication. Please check with your local library or contact Susan Frankel for information on obtaining this publication.

Prior symposia proceedings:

Sudden Oak Death references

Insect and Disease Response to Climate Change

Forest plant diseases are heavily influenced by weather and climate. For forest pathogenic fungi, bacteria, viruses and other microorganisms, the temperature and moisture conditions interacting with the host determine infection severity and disease distribution. Extreme weather, i.e. drought or typhoons, can kill large expanses of trees directly by overwhelming tree physiological and structural strength. Patterns and rates of wood decay, caused by forest fungi, are also expected to change in response to climate changes which will influence forest carbon cycles. Expected changes in climate coupled with the increasing stresses of invasive species, lack of fire, and forest fragmentation are creating conducive conditions for many forest plant diseases.

Forest Disease (Contact: Susan Frankel)

White Pine Blister Rust in Western North America

A disease native to Asia, white pine blister rust was introduced separately into both eastern and western North America early in the 20th century. In both cases, the vector was seedlings of native eastern white pine imported from European nurseries, where they had become infected. Blister rust had first appeared in Europe in the mid-nineteenth century, and within three decades had spread across the continent wherever the popular eastern white pine had been planted. More about this topic. [under forest genetics]

Last Modified: Mar 28, 2013 03:33:58 PM