Firewood movement is one way in which invasive plant pests and diseases can be transferred from one location to another, often resulting in devastation to natural resources. In an attempt to more effectively plan for and mitigate against potential threats to California’s urban and wildland forests, this document analyzes what is currently known about firewood movement into and within the State.
Roughly 99.8% of California’s land area is located within 50 miles of a State Park, National Park, or National Forest. Therefore, any introduced pest is a potential threat to the State’s outdoor recreation and natural conservation areas, as well as forest resources.
California has 16 border stations along major highways that monitor vehicles coming into the State for unwanted pests associated with commodity products. In addition, there are 20 Homeland Security Custom Border Protection stations at international land, air, and seaports of entry, of which six service ports statewide handle commercial shipments and 14 handle individuals and their personal property.
Firewood Movement into California
With California being the 11th largest economy in the world (reference http://www.ccsce.com/PDF/Numbers-Jan-2012-CA-Economy-Rankings-2010.pdf), trade and travel continue to bring vast amounts of firewood into the State annually. In 2009, California received direct international shipments of firewood from Estonia, Honduras, Japan, Latvia, and Sweden. In 2010, more than 27.5 million private vehicles and 7 million commercial vehicles were inspected at California’s border protection stations (reference: http://www.cdfa.ca.gov/phpps/pe/ExteriorExclusion/borders.html).
This year, the USDA Forest Service, Region 5 performed an analysis of 2011 firewood-related Pest Detection Reports (PDR) generated by the California Department of Food and Agriculture (CDFA) regarding incoming firewood at the 16 State border stations to determine: 1) how much firewood is entering the state; 2) where the firewood is coming from and going to; 3) what forest pests have been intercepted on firewood entering the state, as well as the origin and destination of each load; and 4) what the potential threats are to California forests and parks from pests transported via firewood.
Firewood results for 2011
- Almost 23 million pounds (lbs) of firewood were recorded in 8,400 individual loads.
- Top entry points by weight were Hornbrook (8.8 million lbs), Redwood Highway (5.4 million lbs), Alturas (1.9 million lbs), and Yermo (1.7 million lbs).
- Nearly 63 percent of the firewood by weight was in commercial vehicles, but represented only 10 percent of the total number of individual loads.
- Firewood came to California from 46 other states, Canada, and Mexico. Top firewood origins by weight were Oregon (13 million lbs), California (2.9 million lbs), Canada (2.7 million lbs), and Utah (1.2 million lbs).
- Firewood was being taken to over 550 named destinations, the vast majority of which were in California (500 locations; 20 million lbs). Most of the rest was being taken to Reno, Nevada.
- Calculated as straight-line distances between border stations and named destinations, firewood in commercial vehicles was expected to travel twice as far on average then wood in private vehicles (193 miles versus 78).
- The average distance firewood was expected to travel varied widely between the border stations. Wood entering the state at Needles (268 miles), Hornbrook (192 miles), and Vidal (179 miles) traveled the furthest while wood entering at Winterhaven (8 miles) and Alturas (18 miles) tended to stay very local.
Potential Forest Pests Found in 2011
- Border stations intercepted 337 potential forest pests in firewood.
- Of the intercepted pests, 93 percent were beetles. No major United States invasive exotic pests were intercepted in 2011; however, in 2010, emerald ash borer was intercepted in firewood from Michigan.
- Potential forest pests came to California from 38 other states and Canada (Map 2). Top origins were Oregon (38 pests), Arizona (34 pests), Colorado (28 pests), and Texas (26 pests).
- Of the intercepted pests, 26 percent were in vehicles with California license plates, bringing wood back to California from at least 19 other states.
- Identified infested wood was being transported to 120 destinations, with major California cities and Yosemite National Park among the most common.
This initial analysis shows that movement of firewood across California’s borders may be an important pathway for invasive forest pests and diseases to enter the State, and highlights how border inspection stations are an important stopgap. However, firewood is still able to enter the state unchecked through entry points other than main border station locations and through state border stations during hours of non-operation. Additionally, the future of many border stations is uncertain given the current poor economic climate. Still needing examination for a full understanding of firewood movement into and within California are the international ports of entry.
Local Movement of Firewood in California
A USDA Forest Service, Region 5 analysis of Forest Service non-commercial firewood cutting permits issued for National Forests from 2000 to 2011 provide a cursory view of how locally cut wood for personal use is moved.
Map A and B show movement of permitted cut firewood off of three National Forests. The green lines track the origin of the cut wood back to the zip code logged for each permit given. Thicker lines indicate greater firewood movement to a given location. Both maps represent forests where invasive species have become established and are causing massive die-off of certain tree species. This may have implications for accidental movement of invasive species in San Diego County (goldspotted oak borer - Cleveland National Forest) and along the North Coast (sudden oak death - Mendocino and Six Rivers National Forests).
Regional Movement of Firewood in California
Yosemite National Park campground case study: In 2009, 10 campers in Yosemite were asked about their firewood habits when camping. Campers came from a variety of areas, including coastal California (70 percent), eastern California (10 percent), and out of state (10 percent).
Firewood: Ten percent of the campers brought wood from their own property, 10 percent purchased boxed wood within the park, and 20 percent brought in wood they had found at other camps. Forty percent planned to burn all of their wood onsite, 30 percent planned to take the remaining wood home, and 20 percent of campers planned to leave the unburned wood onsite.
Pests: Thirty percent of the campers were aware of State quarantines regarding firewood and pests; however, 10 percent brought banned host material anyway. While none of the campers had observed insect activity on their firewood, careful inspection by the ranger found that 40 percent of the wood inspected had visible insect galleries.
Statewide Movement of Firewood in California
An analysis of California’s commercial firewood importation, exportation, and movement within the State is underway. Larger commercial firewood dealers nationwide are moving toward a third-party certification program for firewood, with all wood kiln dried and meeting various standards of excellence that will be classified as gold, silver, and standard. More on the certification program and the American Firewood Producers and Distributors Association can be found at http://afpda.alreadysetup.com/.
BERKELEY - Because the past rainfall year was relatively dry, the leaves of many oak trees in the Sierra Nevada and Coast Ranges have been turning brown, and some trees have even begun losing their leaves.. Several native California oaks, including California black oak (Quercus kelloggii) and blue oak (Q. douglasii) have exhibited these symptoms. Both of these deciduous species lose all of their foliage in the fall, but in late -summer they are normally green and leafy. A number of landowners have contacted their University of California Cooperative Extension county offices to find out what is causing the problem and whether their trees are in jeopardy.
While early leaf drop is unusual, it has happened many times before during dry years. In the severe drought of the mid-70s and again in the late 80s, some trees lost all of their foliage by mid-August. For this reason, several deciduous native California oaks – especially blue oak are labeled as “drought deciduous”. This simply means that they lose their leaves early in response to extremely dry soil conditions. This is apparently an adaptive mechanism to prevent lethal desiccation by eliminating transpirational moisture loss that can occur as long as the leaves are present on the trees.
The immediate effects of this leaf loss may be startling, but there should be little long-term impact on tree health, according to Doug McCreary, a Natural Resources Specialist Emeritus.
During the coming months, trees may continue to lose their leaves, McCreary says. There is also a strong possibility that many trees will grow new leaves before the fall, especially trees that lost their leaves relatively early in the season.
“Tree vigor also helps determine the amount of refoliation, since trees with more energy reserves are better able to refoliate than weakened trees,” McCreary said. “Trees with pre-existing stress, or infected trees that lose their foliage relatively late in the season, may not refoliate as fully. They may also experience some dieback in the crown.”
The leaf loss reduces the tree’s ability to manufacture food through photosynthesis and over time, repeated defoliations could weaken trees. But since these events are often widely spaced, long-term tree health is usually not seriously impacted. “Next year,” McCreary says, “it will probably be very difficult to tell which trees lost their leaves early, and which remained foliated late into the season.”
For more information about oaks and oak management and the names of experts working with oaks by region, visit the University of California’s oak conservation website at: http://ucanr.org/oaks. For information about sudden oak death, visit the Web site of the California Oak Mortality Task Force at: http://www.suddenoakdeath.org/.
Douglas McCreary, University of California natural resources specialist, (530) 639-8807, firstname.lastname@example.org
- Author: Katharine Palmieri
- Editor: Sophie Kolding
The 5th Sudden Oak Death Science Symposium, held in Petaluma, CA June 19 – 22, 2012, brought together researchers, regulators, land managers, and industry representatives from throughout the world working on Sudden Oak Death (SOD), Phytophthora ramorum (the pathogen known to cause SOD), and other related forest and nursery pests. The Symposium included 52 talks and 25 posters from top researchers around the globe as well as a “SOD: Biosecurity Concerns and Forest Restoration” field trip, where attendees heard about international plant hunters and biosecurity risks related to plant hunting and walked through a local preserve, learning about long-term system changes and restoration efforts following SOD outbreaks. There was also a community “Ask the Expert” evening session where the public was able to talk one on one with researchers and outreach specialists, and a special tanoak session was offered on Friday, focusing on the history, values, and ecology of tanoak.
Highlight findings from the meeting included the discovery of a 4th P. ramorum lineage, the announcement that pathogen sporulation has been found on non-symptomatic Japanese larch needles, and learning that 85 percent of the Marin Municipal Water District’s susceptible habitat is now infested.
If you missed the Symposium, be sure to visit the website (http://ucanr.org/sites/sod5/) where you can access the agenda, book of abstracts, and link to the archived live stream that was made available throughout the meeting for those unable to attend.
- Editor: Sophie Kolding
- Author: Brice McPherson
The Sudden Oak Death (SOD) epidemic in East Bay Park District forests dominated by coast live oaks, Quercus agrifolia, and bay laurels, Umbellularia californica, presents major management challenges. Coast live oaks play a disproportionately large role in these forest ecosystems even when they are not the dominant overstory tree species. There are no other tree species in these forests that support as many other organisms (insects, bird, mammals, and fungi) as well as produce high quality protein in the form of acorns. In addition to problems faced by other forests at the urban-wildland interface, such as invasive plants and degraded habitats, managers of these lands must now contend with the effects of Phytophthora ramorum, the pathogen that causes SOD.
Figure 1. In coast live oaks, sudden oak death exhibits a predictable, progressive sequence of symptoms.
Phytophthora ramorum is a water mold apparently introduced through the nursery trade from Asia. This organism, unknown prior to 2000, infects a remarkably large number of native plant species, causing different diseases in different species (Rizzo and Garbelotto, 2003). Typically these infections take the form of leaf or stem lesions and are not fatal. However, most oaks native to California that are in the red oak group (section Lobatae), which includes coast live oaks, are highly susceptible to the pathogen. Infection in oaks follows a consistent sequence: 1) a viscous exudate, referred to as bleeding, appears on the bark, typically no higher than about 1.5-m above the soil; 2) both ambrosia and bark beetles tunnel into these infected patches (often 10-15 cm deep into the sapwood); 3) fruiting bodies of fungi appear on the bark above the beetle tunnels; and 4) tree death follows (Figure 1). Because of beetle and fungus damage, up to 25% of infected coast live oaks may fail while still alive, typically snapping within 2-4 feet above the soil (McPherson et al., 2010). In the course of maintaining long-term study plots in Marin County, we have identified critical parameters for understanding the response of coast live oaks to infection by P. ramorum (McPherson et al., 2010) (Table 1).
Table 1. Survival estimates (years + standard error) for coast live oaks infected by P. ramorum in two Marin County forests, 2000-2008, based on Weibull survival models (McPherson et al., 2010). CCSP: China Camp State Park; MMWD: Marin Municipal Water District.
Median survival, CCSP
Median survival, MMWD
Bleeding + Beetles
Management of forested ecosystems that are being affected by this introduced pathogen depends critically on understanding the magnitude of the threat. The Park District was aware that P. ramorum had been detected in their forests as early as 2001, but in the absence of knowledge of the distribution and severity of the problem, rational management plans cannot be developed. Beginning in 2009, with funding from the Park District, a team consisting of David Wood, Greg Biging, Maggi Kelly, Brice McPherson, and numerous field workers initiated a project to map the location and severity of SOD in coast live oaks in the five major forested parks that lie along the East Bay Hills using a network of permanent plots. These parks are Wildcat Canyon and Tilden Regional Parks, Huckleberry Regional Botanic Preserve, and Redwood and Anthony Chabot Regional Parks. These all lie directly east of densely settled Richmond, El Cerrito, Berkeley, Oakland, and San Leandro. The goal of this study is to develop models of change in disease incidence and severity and to predict future stand characteristics.
Figure 3. Plots in Redwood Park with both symptomatic and dead coast live oaks. Image produced by Sam Blanchard, GIF Berkeley.
Analysis of the Redwood Park survey data illustrates this approach. We used geographic information system (GIS) technology and GPS devices to locate 105 plot sites randomly assigned within oak-bay habitats that were identified by vegetation type maps. Stand characteristics recorded for each plot include stem diameter at breast height (DBH) for every woody plant >2 cm DBH, health of each stem, and recruitment of woody plants, estimated by counting the seedlings and saplings in two linear transects. Dead, previously infected trees are reliably identified by extensive beetle tunneling and associated fungal activity.
In Redwood Park in 2011, 19% of the coast live oaks in plots were symptomatic or killed by SOD. Comparison with the situation in Marin County in 2003 implies that considerably greater impacts are yet to come in East Bay forests (Figure 4). Resulting maps for Redwood Park show large spatial variation in the presence and severity of infected coast live oaks and differences in the proportions of trees in different stages of the disease (Figures 2 and 3). Note that in 2011 there were areas in Redwood Park with little or no actively detected bleeding coast live oaks (green) but with trees already killed by SOD. Because SOD is a progressive disease (i.e., unidirectional), knowledge of the distribution of the disease stages can be used to project stand-level change and to infer the history of the disease at a site.
Figure 4. Percentages of coast live oaks with symptoms of P. ramorum infection and those that died with these symptoms. The year indicates when each survey was done.
The data for the different stages of SOD will be used to develop a predictive model to facilitate management of these forests as the epidemic continues and expands into previously unaffected stands. Although no cure or treatment is likely to prevent further wildland infections and mortality, the ability to make data-based predictions at the landscape scale will enable planning decisions to be based on a factual foundation.
This work was initiated in collaboration with Nancy Brownfield, East Bay Regional Park District IPM Specialist, who died recently. Her presence will be missed.
McPherson, B.A., Mori, S.R., Wood, D.L., Svihra, P., Kelly, N.M., Storer, A.J., and Standiford, R.B. 2010. Responses of oaks and tanoaks to the sudden oak death pathogen after 8 y of monitoring in two California forests. Forest Ecology and Management 259: 2248-2255.
McPherson, B.A., Mori, S.R., Wood, D.L., Storer, A.J., Svihra, P., Kelly, N.M., Standiford, R.B. 2005. Sudden oak death in California: Disease progression in oaks and tanoaks. Forest Ecology and Management 213:71-89.
Rizzo, D. M., and M. Garbelotto. 2003. Sudden oak death: endangering California and Oregon forest ecosystems. Frontiers in Ecology and Environment 1:197-204.
- Editor: Sophie Kolding
- Author: Jan Gonzales
The goldspotted oak borer (GSOB; Agrilus auroguttatus) continues to attack and contribute to the high mortality of tens of thousands of oaks in San Diego County and the threat to oaks throughout southern California remains a considerable concern. In effort to inform professionals who are responsible for the stewardship of oaks and oak woodlands, a series of workshops has been offered in six southern California counties in which oaks may be at risk: Ventura, Los Angeles, Riverside, San Bernardino, Orange and San Diego. The overlying objective was to spread the knowledge of goldspotted oak borer and minimize the spread of this non-native insect into new areas. These day-long events offered multi-agency presentations, hands-on displays, outreach materials and in some locations, short field trips.
Figure 1. Dead oak trees due to GSOB Figure 2. Two Adult GSOB on penny
(Photo source: Tom Coleman, USDA Forest Service) (Photo source: Tom Coleman, USDA Forest Service)
In cooperation, the USDA Forest Service, CAL FIRE, and the University of California have partnered with other local agencies, tribes and organizations to provide these workshops. Presenters at each session were coordinated from a cadre of specialists and researchers. Key speakers included Tom Coleman, Paul Zambino, Sheri Smith, Larry Swann, Lisa Fischer and Matthew Bokach (USDA Forest Service and Forest Health Protection); Tom Smith, Kim Camilli and Kathleen Edwards (CAL FIRE);Tom Scott, Doug McCreary, Jim Downer and Kevin Turner (University of California Cooperative Extension); and Vanessa Lopez (PhD candidate in the Entomology Department, UC Riverside). Introductory workshops were held monthly from September 2010 through February 2011. Topics covered were:
- GSOB history and distribution
- GSOB identification and biology
- Ecological and economic impacts of infested oaks and oaks at-risk
- Integrated best management practices for GSOB infested and at-risk oak woodlands
- How to prepare for potential outbreak
- Utilization of GSOB infested oak wood
- Restoring oak woodlands impacted by GSOB
Figure 3. Larvae Feeding Galleries, seen in cambium Figure 4. GSOB larvae in firewood (Photo source:
of oak wood cross-section (Photo source: Tom Scott, UC Cooperative Extension)
Kim Camilli, CAL FIRE)
In early May 2012, two additional workshops were held to provide updates from on-going research, best management practices and mitigation and education efforts. The session on May 1st was held in Altadena in partnership with the Los Angeles County Fire Department-Forestry Division and the County Parks and Recreation Department. The following workshop, held on May 2nd, was hosted in partnership with the Pechanga Band of Luiseño Indians in Temecula.
- The goldspotted oak borer in an introduced, non-native beetle attacking and killing coast live oak (Quercus agrifolia), California black oak (Quercus kelloggii), and canyon live oak (Quercus chrysolepis) trees in San Diego County.
- The adult goldspotted oak borer (GSOB) Agrilus auroguttatus is a small, bullet-shaped beetle about 10mm (0.4 in.) long and has six golden yellow spots on its dark green forewings.
- Mature larvae are white, legless, slender and about 18mm (0.75 in.) long with two pincher-like spines at the tip of the abdomen. Larvae feed under the bark on the trunk and larger branches.
- Larval feeding kills patches and strips of cambium tissue beneath the bark, which causes dark staining and sap flow. The larvae pupate in the outer bark and leave D-shaped exit holes about 1/8 in. wide when they emerge.
- GSOB produce only one beetle generation per year.
- The goldspotted oak borer’s peak flight and breeding season is May through October.
- There is on-going research being conducted on biological and chemical GSOB control methods for preventative management; trees at various degrees of infestation; and the wood from infested, dead and felled trees.
- Currently, there are no effective treatments that can eradicate GSOB once it becomes established.
- Goldspotted oak borer larvae and pupae can survive under the bark of wood from large branches and trunks for up to a year after a tree dies.
- Currently, best management practices to minimize introduction of GSOB to new areas is to let wood cure at least two years after the tree dies before moving firewood from infested areas or grind wood into 3-inch particles.
- Before any type of treatment on oaks is initiated for GSOB infested trees or as a preventative measure on high-valued trees, a management plan should be developed first.
- There are no quarantines or zones of infestation in place by statewide authorities for GSOB; however, in 2011 the California Pest Council established the California Firewood Taskforce, a coalition of stakeholders that initiates and facilitates efforts within the state to protect our native and urban forests from invasive pests that can be moved on firewood.
- The Early Warning System is a citizen scientist program established to enlist the help of those concerned about oaks for the purpose of identifying oak tree health in southern California urban and woodland areas.
- Information and resources may be found on the Goldspotted Oak Borer website, www.gsob.org. To stay informed of current news, information and future training opportunities, we recommend you join the GSOB email list.
Figure 5. Tom Scott Workshop speaker
(Photo source: Lorin Lima, UC Cooperative Extension-San Diego)
Nearly 500 professionals attended these workshops. Findings from follow-up workshop surveys indicate that potentially more than 2,600 others will learn about GSOB through outreach extended by workshop participants. Although evaluation and survey responses point towards a successful series of GSOB workshops, the threat of further goldspotted oak borer attacks remains. As the peak emergence and flight season occurs during the same time of year of increased vacation travel and camping in southern California, we are all encouraged to share the news about GSOB and it’s threat to oaks with others along with the message to not move firewood – “Buy It Where You Burn It.”
For more information:
Goldspotted Oak Borer website: http://www.gsob.org
California Firewood Task Force: http://www.firewood.ca.gov
Goldspotted Oak Borer - The Center for Invasive Species Research, UC Riverside:
Goldspotted Oak Borer – UC Statewide Integrated Pest Management: http://www.ipm.ucdavis.edu/NATURAL/index.html