SUDDEN OAK DEATH DISTRIBUTION, DETECTION,

AND HOST RISK MODELING

A. Statement of the Problem

California's oaks are an essential part of our heritage and natural landscape. In recent years, an alarming disease has been killing oaks in the Central Coast of California. The cause of this disease was identified only two years ago as a newly described pathogen, Phytophthora ramorum. The disease this pathogen causes on oaks is called Sudden Oak Death (SOD). The trees appear to die rapidly; however, trees in which foliage rapidly turns brown are likely to have been infected for more than one year. Since 1995, SOD has been confirmed in California from southern Mendocino County to Big Sur, Counties, as well as in Curry County, Oregon, and is particularly severe in Marin, Santa Cruz, and Monterey Counties in California. Dying trees have been observed in urban interface and rural forests and woodlands. The actual current geographic range of SOD Phytophthora ramorum is unknown. The main overstory plant species affected are coast live oak (Quercus agrifolia), California black oak (Q. kelloggii), and tanoak (Lithocarpus densiflorus). The disease also affects Shreve's oak (Quercus parvula shreveii), huckleberries (Vaccinium ovatum), madrone (Arbutus menziesii), manzanita (Manzanita arctostaphylos), toyon (Heteromeles arbutifolia), California laurel, (Umbellularia californica), California buckeye (Aesculus californica), bigleaf maple (Acer macrophyllum), rhododendron (Rhododendron spp,), coffeeberry (Rhamnus californica), honeysuckle (Lonicera spp.), and arrowroot in Europe (Viburnum). Concern exists that the pathogen may spread throughout California oak forests, be transported to the forests of other western states, and even be spread to the eastern United States. This long-range transport was likely confirmed in the summer of 2001 with the discovery of the pathogen in Southern Oregon in Curry County. With discovery of the pathogen on rhododendrons, there exists a much greater risk of human transport of the disease via ornamental plants. Thus, the disease has the potential of becoming widespread, both in afflicted species and in geographic range.

A comprehensive statewide survey for SOD is required for regulatory action to limit the spread of this pathogen problem. Without comprehensive accurate distribution information the necessary regulations for restricting transport of infected materials cannot be formulated nor enforced. These regulations are necessary to prevent the spread of the disease to other areas and landscapes, and to commercial operations outside of the area currently affected. Host maps are necessary to assess the risk that the pathogen will spread into new areas. These maps can be used to plan survey work and control strategies and to test the effectiveness of regulations. In order to identify the pathogen, laboratory analysis procedures and techniques will be provided by Dave Rizzo, UC Davis, and Matteo Garbelotto, UC Berkeley. This is critical to the success of the statewide survey

The California Oak Mortality Task Force (COMTF) has established an extensive monitoring program and its websites allow the public to submit reports of possible occurrences of SOD. Research and outreach efforts are hindered by serious gaps in our knowledge of the pathogen. How the pathogen spreads across California's landscape is unknown, and we have limited ability to predict which stands of trees are at high risk of infection.

We have assembled a team of USDA Forest Service, California State University (CSU), and University of Californai (UC) researchers to address these needs by studying fronts of infection and overall state distribution of SOD. Team members include employees at the USDA Forest Service Forest Health Project (USFS FHP), in Sacramento, faculty members at Sonoma State University (SSU), California Polytechnic State University, San Luis Obispo (CPSLO), UC Davis, and UC Berkeley. Our goal is to accurately determine the range of SOD and to identify infected trees. Our work is unique because we bring together scientists with expertise in plant pathology (Dr. Walter Mark, CPSLO, Matteo Garbelotto, Berkeley, and Dr. Dave Rizzo, Davis), remote sensing (Maggi Kelly, UC Berkeley, Lisa Levien and Jeff Mai, USFS FHP in Sacramento) geographical analysis (Dr. Ross Meentemeyer, SSU).

B. Statement of Methodology and Objectives

We propose a coordinated approach for the Statewide Survey of Extent of SOD project, with the following objectives.

We will participate in a statewide survey of the species susceptible to SOD. This will be accomplished by an aerial survey of the state inside and outside of the known infested counties to assess the extent and distribution of SOD in the State. This is a coordinated effort of many groups and we will be working with the USDA Forest Service group’s SOD roadside survey, the CPSLO understory foliar host survey, and the US Forest Service Forest Health Project Statewide Landcover Monitoring Program from 2001, no data is available from the Landcover Monitoring Program 2002 due to lack of funding. We will conduct ground checks of susceptible hosts and compare these results to data obtained from the aerial survey as well as the USDA Forest Service change analysis maps. The aerial survey will work with newly created maps that combine existing resources including USGS quad maps, orthographic photos, the California vegetation map and the gap analysis of vegetation. All the aerial survey will be conducted within a window of June 1 to July 15, 2002. The USCA Forest Service Forest Health Project in Sacramento will conduct the aerial survey for infested counties from Santa Cruz County north (Santa Cruz, San Mateo, San Francisco, Marin, Sonoma, Napa, and Mendocino), as well as for Humboldt and Del Norte Counties. . In addition the USDA Forest Service FHP(USDA FS FHP) will head up aerial survey of the Sierra Nevada foothill band of black oak, with possible assistance of Bill Woodruff for the Northern Sierra Nevada. CPSLO will conduct the aerial survey for Monterey County south as well as all border counties on the eastern edge of the infested counties (Monterey, San Benito, Fresno, San Luis Obispo, Kern, Santa Barbara, Ventura, Los Angeles, Solano, Yolo, Lake, Glenn, Tehama, Trinity, and Siskiyou). The East Bay counties of Santa Clara, Alameda, and Contra Costa will be surveyed jointly by the USDA FS FHP and CPSLO. The USFS FHP will compile results from the entire aerial survey and provide the data to support the ground follow-up. This will include flightline and polygon maps, polygon data sheets, and polygon photographs taken from the air. The USDA FS FHP and CPSLO will coordinate prioritization of the maps to produce.

The aerial survey work must be verified on the ground to determine that detected symptomatic trees and plants are affected by P. ramorum rather than other factors that result in a similar signature. Ground survey follow-up work will be conducted from June through September 2002. Samples will be collected from suspected SOD hosts for isolation and identification at UC Davis (previously uninfected counties) and the CDFA Laboratory (known infested counties). The ground survey will detect SOD in understory plants that are not visible from aerial surveys. The ground survey is therefore required for the distribution study. This is important for tanoak mixed with conifers, coast live oak mixed with conifers, huckleberry, Shreve's oak, all understory species susceptible as well as the foliar hosts such as California laurel, California buckeye, madrone, manzanita, and native Rhododendron populations. Survey results will be provided to the GIS team (see below) for use in spread and risk modeling. Ground follow-up work will be divided with the USDA FS covering all the area starting with Marin and Contra Costa Counties north and CPSLO covering the area from San Francisco and Alameda Counties south. Areas of USDA FS and CPSLO responsibility to this project are fairly rigid, however, minor deviations may be coordinated in order to improve logistics and reduce costs as we begin implementation of survey and groundwork. Of course, groundwork will be very specific prior to execution of the contract to be administered by the USDA FS.

Geographical surveys will provide many samples from symptomatic plants differing in severity of SOD infection, from a variety of sites, and from adjacent non-symptomatic plants. Confirmation of the presence of SOD requires culturing Phytophthora from specimens collected in the field. This method is time consuming, costly, and prone to problems, especially false negatives, when samples are not collected and cared for properly. This work will be done by Dave Rizzo’s lab in Davis and the CDFA Laboratory. Matteo Garbelotto at UC Berkeley has identified a genetic marker for Phytophthora ramorum. The marker exists in the Internal Transcribed Spacer (ITS) region of ribosomal DNA. From the DNA sequence differences between this pathogen and other species of Phytophthora, allele-specific primers exist that can be used to amplify the pathogen from host tissue by polymerase chain reaction (PCR). This recently developed test that detects Phytophthora ramorum DNA will also be used for survey samples, and testing will be provided by Matteo Garbelotto’s laboratory. We will combine information from genetic tests with survey information to maximize accuracy of our assessment of SOD spread. This is a necessary step in developing a predictive model.

C. Results Dissemination Plan

We will disseminate our results to members of the public, press, and scientific community using traditional methods and emerging technologies. Our intention is to reach as wide an audience as possible. This is especially critical as public awareness and concern about SOD has reached a high point and it is essential that scientifically accurate information be conveyed to minimize spread of the disease to new regions. Our specific approach will be as follows:

1) Participate in the California Oak Mortality Task Force (COMTF) Meetings and present information on the project progress and results at those workshops. Presentations have already been made by Dr. Mark at the April, 2001 workshop in Felton on other diseases that may be confused with SOD and at the November 2001 COMTF meeting in Petaluma on the plan for surveying for SOD in California. Dr. Mark (CPSLO) is the Co-Chairman of the COMTF Monitoring Committee and Lisa Levien and Jeff Mai (USFS FHP) and Ross Meentemeyer (SSU) are members of the committee.

2) Provide data on the survey results to the COMTF webpage that reports the known distribution of SOD in California. The California Department of Food and Agriculture utilizes this information to enforce the regulations on movement of Phytophthora infested plant material. These pages will provide up-to-date information on our progress and links to sources of information about SOD from the University of California and the media.

3) Involve students from the SSU Department of Geography and CPSLO Department of Natural Resources Management in our efforts to study SOD. This initiative would build on existing programs. Since November 2000, over 50 students from SSU's Department of Biology students have participated in SOD surveys at FOP. We will add laboratory exercises that emphasize SOD to one Geography course and one Forestry and Natural Resources course.

4) Maintain regular contacts with representatives of the media by PI's and personnel. Several reporters from newspapers, radio and television stations have contacted the PI’s about the status in SOD in the State. A letter will be drafted April 2002 for the COMTF notifying County Ag Commissioners of our intent to conduct air and ground surveys. This will serve to open and improve early communication. Results will be provided on the web and, similarly, will be provided via hardcopy maps and acreage summaries to pertinent Ag Commissioners.

5) Continue to participate in Oak Symposia. A paper was presented by Dr. Mark at the 5^th California Oak Symposium in San Diego in October 2001. This presentation was on the progress on surveys for SOD and the plans for future survey efforts. Lisa Levien of the US Forest Service FHP in Sacramento presented a paper on multiscale remote sensing for SOD, the Aerial Survey of 2001, and digital camera images.

6) Present our results at nationally recognized scientific conferences. The survey study results were presented at the Fifth Oak Symposium in San Diego in October 2001. Presentations were also made on surveying for rare events in forest health and aerial survey methods at the Western International Forest Disease Work Conference in Carmel, September 2001 by Dr. Mark and Lisa Levien from the USFS. Dr. Mark also led one group on the field trip on SOD in the Big Sur area as part of this meeting.

7) Publish our results in academic refereed journals. The presentation at the 5^th California Oak Symposium was peer reviewed. Related presentations at the Ninth Biennial Remote Sensing Applications Conference 2002 will also be peer reviewed. (Several of the investigators are doing presentations or posters that may touch on SOD work done to date)

8) Present reports and maps to USDA Forest Service and California Department of Forestry and Fire Protection on the extent of the distribution of SOD in fall 2002 and every fall through 2004, assuming continued funding for annual survey work. Lisa Levien presented a paper on multiscale remote sensing for SOD, the Aerial Survey of 2001, and digital camera images at the Forest Health Monitoring Work Group in New Orleans in February 2002.