Treesearch

Phytophthora de Bary, a genus of Oomycetes, is known as a plant pathogenic genus. The best-known species infect a wide range of hosts, including economically valuable angiosperm and gymnosperm tree species and important agricultural crops. Many Phytophthora are invasive and have been disseminated through nursery and agricultural trade. We hypothesize that such human activities would affect the diversity of these pathogens. To test this hypothesis, we characterized and compared Phytophthora diversity between natural and urban environments in British Columbia. We collected soil samples from...

Acute Oak Decline (AOD) is a complex disease syndrome of native oak, making its first appearance in the 1980s in Britain. Since then increasing reports of its occurrence have raised concerns about cause and effects on these iconic trees. Symptomology studies confirmed that AOD is a distinctive condition with four diagnostic symptoms defining the condition; (a) weeping patches on trunks of affected trees, (b) cracks between the bark plates, (c) inner bark necrosis and sapwood degradation underlying the weeping patches, (d) over 95% co-occurrence of larval galleries of a native bark boring...

In recent years, a novel form of decline has been observed in southern and central England. This syndrome has been termed acute oak decline (AOD) and affects native oak, Quercus petraea and Q. robur. Typical symptoms include bark cracks that weep dark exudates, which are caused by necrotic patches in the inner bark. Studies show bacteria are consistently isolated from lesion edges, with two species, Gibbsiella quercinecans and Brenneria goodwinii, thought to cause tissue necrosis. Agrilus biguttatus (a native beetle, with apparently increasing populations) is often reported at affected...

A strong focus on tree germplasm that can resist threats such as non-native insects and pathogens, or a changing climate, is fundamental for successful conservation efforts. This project is predicated on the fact that genetic resistance is the cornerstone for protecting plants against pathogens and insects in environments conducive to the attacking organisms, a principle we have extensively applied to the study of coast live oak (CLO – Quercus agrifolia) interactions with Phytophthora ramorum in California wildlands. The largest obstacle to the implementation of host resistance as a tree...

Over the past 15 years, the USDA Forest Service, Pacific Southwest Region, State and Private Forestry (S&PF) has provided grants which have supported over 200 projects to address sudden oak death (SOD) in California. To date, over $10 million has been provided by US taxpayers, plus an additional $8 million of non-federal matching funds. These funds have provided the infrastructure for California’s SOD response: supporting laboratory diagnostics, monitoring, management, and education and outreach. Grantees have included CAL FIRE, five California universities, UC Cooperative Extension in...

In 2006, three isolated sudden oak death- (SOD) infested locations within Humboldt County were selected for silvicultural treatments that targeted the removal and/or reduction of tanoak (Notholithocarpus densiflorus Hook. & Arn.) and California bay laurel (Umbellularia californica Hook. & Arn), the main hosts supporting sporulation of Phytophthora ramorum (Valachovic and others 2010). In these treatment areas, subsequent rates of infection on re-sprouting tanoak and bay laurel varied widely, but were very low where bay laurel was either absent or in low densities at the time of treatment....

Forest CO2 emissions, which have recently become a more regular concern in forest management, can radically increase following pest and disease outbreaks. We inventoried trees in a stand adjacent to an infested area in northern Humboldt County, California, and used a stand-level dynamic disease model to forecast Phythophthora ramorum-caused tanoak mortality with and without a proposed treatment to mitigate disease spread and impacts. Using forest growth simulations employing model-predicted mortality rates, a proposed treatment that removes California bay laurel and reduces tanoak stem...

On Mt. Tamalpais, after nearly 20 years of accumulated disease impacts, some tanoak- (Notholithocarpus densiflorus) dominated forests where Phytophthora ramorum first emerged have converted to brushy fields of tanoak resprouts. Phytophthora ramorum has invaded throughout the greater San Francisco Bay Area, and damaged the culturally, ecologically, and economically important forests of Mount Tamalpais, including many stands managed by the Marin Municipal Water District (MMWD) for water yield and recreation. Sustained inoculum loads have resulted in extensive tanoak mortality, in some places...

Since 2001, approximately 5,350 acres of tanoak forests in Curry County, Oregon have been treated to eradicate Phytophthora ramorum and slow the spread of sudden oak death. Over 1,300 of these acres are on lands administered by the USDI Bureau of Land Management (BLM CB), Coos Bay District and the USDA Forest Service, Rogue River-Siskiyou National Forest (USFS RRS). Treatments include using herbicides to reduce tanoak sprouting, cutting, piling and burning known infected tanoaks, and cutting, piling, and burning exposed tanoaks and other selected hosts in a buffer area around known...

Prior to 2000 the etiology, effects on host trees, and possible consequences for northern California’s forests of the syndrome known as sudden oak death were unknown. We designed a plot-based study to address these issues and to set a baseline for future evaluations. In March-April 2000 we established a total of 20 plots in two forested areas in Marin County: China Camp State Park [CCSP] (10) and Marin Municipal Water District [MMWD] (10). The host species monitored were coast live oak [CLO] (Quercus agrifolia) and California black oak [CBO] (Q. kelloggii) in both sites and tanoak [TO]...