Invasive Forest Diseases

Sudden oak death (SOD) is caused by the water mold Phytophthora ramorum. Since 2000, it has caused the death of about 3 million tan oaks and coast live oaks in California. SOD has greatly affected multiple ecosystems along the coast and increased the dead fuels in many communities. For more information, please visit suddenoakdeath.org/.

The Disease: White pine blister rust, Cronartium ribicola, is a fungal disease that infects 5-needled white pines and currant/gooseberry plants in the genus Ribes. While both white pine and Ribes species are native to Asia and North America, the rust fungus was only found in Asia until 1906.

The History: The origin of the blister rust disease that cycles between Ribes and white pines stretches from central Siberia to the Pacific Ocean, and south to the Himalayas (Hummer 2000). White pines from North America were brought to Europe for their use as ship masts in the early 1700s. Reports of white pine blister rust in eastern Europe began in the mid-1800s on these imported trees. Interestingly, nursery stock of white pine was cheaper in Europe than in North America, and the white pine, infected with the rust fungus, was shipped back to North America. The first significant rust outbreak in North America was reported in New York in 1906 and by the 1920s was found throughout the eastern United States. A separate shipment of infected white pine from France to Vancouver in 1910 introduced the disease to western North America (Hummer 2000). By the mid-1960s blister rust was found as far south as the Southern Sierra Nevada mountains (Maloney 2011, Fig. 1). That is as far south as it was known to occur in California until recently. In November 2021, infected Ribes was found in two locations, one near the San Bernardino mountains, and the other in May 2022 near Los Angeles. By the end of 2023, blister rust was observed on five Ribes species in multiple locations running roughly along the southern edge of the Angeles and San Bernardino National Forests. To date, rust has not been observed any 5-needle white pines in the area.

Tree Hosts in California: Bristlecone (Pinus longaeva), foxtail (P. balfouriana), limber (P. flexilis), sugar (P. lambertiana), western white (P. monticola), and whitebark (P. albicaulis) white pines

Ribes Hosts in California: Chaparral currant (R. malvaceum), golden current (R. aureum), hillside gooseberry (R. californicum), Sierra current (R. nevadense), and Sierra gooseberry (R. roezlii)

Other Hosts not confirmed in California: Paintbrush (Castilleja spp.) and lousewort (Pedicularis spp.) species were found to be a host of this rust in Idaho (McDonald et al. 2006), and Oregon and Washington (Mulvey and Hansen 2011)

References:

Hummer, Kim E. 2000. “History of the Origin and Dispersal of White Pine Blister Rust.” HortTechnology 10(3):515–17.

Maloney, P. E. 2011. “Incidence and Distribution of White Pine Blister Rust in the High-Elevation Forests of California: Incidence and Distribution of White Pine Blister Rust.” Forest Pathology 41(4):308–16. doi: 10.1111/j.1439-0329.2011.00732.x.

McDonald, G. I., B. A. Richardson, P. J. Zambino, N. B. Klopfenstein, and M. S. Kim. 2006. “Pedicularis and Castilleja Are Natural Hosts of Cronartium Ribicola in North America: A First Report.” Forest Pathology 36(2):73–82. doi: 10.1111/j.1439-0329.2006.00432.x.

Mulvey, R. L., and E. M. Hansen. 2011. “Castilleja and Pedicularis Confirmed as Telial Hosts for Cronartium Ribicola in Whitebark Pine Ecosystems of Oregon and Washington: Telial Hosts for Cronartium Ribicola in OR and WA.” Forest Pathology 41(6):453–63. doi: 10.1111/j.1439-0329.2010.00702.x.

Past Accomplishments

2005-2009 Sugar Pine Rust Resistance Program Summary:

• 250 MGR families identified from 3314 sugar pine families tested; (total MGR families identified to date = 1,762) .
• 277 sugar pines with both SRR and MGR identified (total trees with both SRR and MGR identified to date = 909)
• 568 sugar pine families screened in 2009; 51 from MGR trees; 5,564 seedlings planted for SRR screening at 2 field sites.
• 52 SRR sugar pines, out of 730, were selected on the Klamath NF for seed orchards in 2009.
• Lake Tahoe area has 13 new MGR trees, totaling 38 MGR trees of 233 tested over 4 years. Southern California has 32 new MGR trees, totaling 63 MGR trees of 860 tested from the 2005 cone collections.

Reforestation of Rust Resistant Sugar Pine (Activities funded by other sources):

• In 2009, cones were collected from 847 sugar pines in northern California for FHP-funded rust screening.
• In 2009, MGR trees in the woods supplied 2,007 pounds of seed, enough for 2.5 million seedlings.
• In 2009, the first significant collection of 48 bushels of cones was made from the youngest of 3 seed orchards targeted for supplying seed to the west side of the Sierra Nevada range.
• In 2009, Placerville Nursery had orders for 441,390 MGR seedlings to be outplanted in 2010.
• More than 1.2M MGR seedlings from Placerville nursery were outplanted between 2005 and 2009.
• Forest industry reports an estimated 2.2M sugar pine seedlings planted from MGR families between 2005 and 2010.
• High-elevation white pine work (FHP funded):
• In 2009, for genetic conservation, cones were successfully collected from 20-25 foxtail, limber, whitebark or Great Basin bristlecone pine trees in each of 6 sites.
• 15 plots established in 2008-09 in foxtail pine stands to supplement plots established in 2004-06 that assess blister rust and other stress factors, and to obtain demographics.
• 123 permanent plots were established from 2004-2006 in high-elevation white pine stands.

Climate Change, Partnerships, and All Lands

The Sugar Pine Rust Resistance staff works on projects associated with any of California’s national forests having white pines as a forest component. The staff also contributes to reforestation programs on State and private lands by providing rust screening service and sharing rust resistant seed and/or materials for mutual benefit to Region 5 and its partners.

The GRP manages seed orchards and clone banks comprised of genetically diverse, broadly adapted trees that are living archives of wild-stand trees spanning a large geographic area and are now maturing for use in seed production. These rust-resistant sugar pine and other white pines will be a valuable source of seed and plant material if climate change creates a need to extend the geographic ranges of these species.

The GRP collaborates with national forest staff in Region 5, the Institute of Forest Genetics, private forest industry, a Tahoe-based non-profit organization, the University of California, and inter-Regionally on projects that overlap in program goals. Primary areas of collaborative work are in seed procurement from MGR trees for the Regional and other seed banks, development and management of seed orchards and clone banks, screening sugar pine and western white pine for MGR and/or SRR resistance, and genetic conservation activities in these and the four higher elevation white pine species in the State.

• White pine blister rust map: consists of reports and survey plots of blister rust. (1929~1966: Bureau Records,1964~present: 1949~1958: Disease Survey Plots)

Pitch canker affects Monterey pine and other related pines and is caused by the fungus Fusarium circinatum. The fungus primarily causes cankers and mortality in apical stems, but occasionally it cause whole tree death. Monterey pines within ~2 miles of the Pacific coast are affected. Many high-value trees have been removed to abate hazards due to tree failure.

• Pitch canker map: consists of two levels of data, confirmed locations (region) and areas at risk > 25% mortality over the next 15 years from pitch canker (poly)

Port-Orford cedar root disease is caused by the water mold Phytophthora lateralis. Dying Port-Orford cedar seedlings were first detected in a Seattle nursery in 1923. Since then, the disease has spread down the Pacific Coast to southern Oregon and some parts of northern California where Port-Orford cedar was growing in native stands of this species. The pathogen is distributed in water and mud.

Port-Orford-cedar (POC) is found on approximately 39,600 acres in Region 5, primarily on the Six Rivers, Klamath, and Shasta-Trinity National Forests and in Redwood National and State Parks. POC grows from sea level to 6,400 feet, with conifer associates ranging from coast redwood to mountain hemlock. Phytophthora lateralis (PL), an exotic root pathogen, was introduced to the range of POC in the early 1950’s. It is almost always fatal to trees it infects. About 10% of the POC acres in Region 5 are infested with PL. PL now occurs in all major watersheds in the range of POC except the Trinity River. Management emphasizes prevention, prompt detection/eradication of new infestations, use of resistant stock for reforestation, and containment of existing infestations.

Region 5 POC program objectives are to maintain POC as an ecologically and economically significant species on National Forest and other lands- not to reduce all risk to all trees at all cost.

Current Issues, Situation, Accomplishments

• Management direction for POC in R5 is in the LRMPs of the Six Rivers, Klamath and Shasta-Trinity NFs. In 2006, detailed guidance and best management practices were provided in the publication, “Managing For Healthy Port-Orford-cedar in the Pacific Southwest Region”.
• Since 2001, the POC Base Maintenance Program has provided a stable funding source for most recurring on-the-ground management costs, including sanitation treatments, seasonal gate closures, effectiveness monitoring, and education/outreach.
• Since 2004, Regions 5 and 6 have been updating POC and PL maps to include common attributes. Region 5 updates were completed in 2010.
• In 2005, new rangewide breeding zones were developed for POC. Region 5 has cooperated with Region 6 in an accelerated PL resistance breeding program. Funding for POC resistance breeding has come from Region 5 POC Base Maintenance and other funds.
• Since 2008, Region 5 FHP staff developed POC Risk Analyses for Motorized Travel Management on the Klamath and Shasta-Trinity NFs and provided POC a risk analysis review for the Six Rivers NF.
• Major POC sanitation efforts were implemented following discoveries of POC root disease in the Siskiyou Wilderness Area (Klamath NF) and at Sanger Lake (Six Rivers NF). POC sanitation at Scott Camp Creek (the only infestation on the Shasta-Trinity NF) has resulted in fewer infested trees being detected.

Climate Change, Partnerships, and All Lands

Operational planting of about 70,000 resistant POC seedlings on areas burned in 2008 was completed during 2009. This was the largest operational planting of resistant POC ever. Planting adjacent to, but outside of, existing POC populations allows for establishment of POC on sites that are marginal for natural regeneration and creates small but immediate expansion of the range of POC. Establishing POC on sites not previously occupied by the species creates greater options for species retention and survival in the face of climate change. 

Partners in the POC program include:

Six Rivers, Klamath and Shasta-Trinity National Forests, Redwood National and State Parks, Castle Crags State Park, Hoopa, Kuruk and Yurok Indian reservations, CALFIRE, Oregon State University, Caltrans, Federal Highway Administration, and Green Diamond Resource Company.