Treesearch

Phytophthora ramorum, causal agent of sudden oak death, continues to threaten U.S. forest ecosystems and the nursery industry. Currently, USDA APHIS’s protocol (2014) utilizes the Bottle of Bait (BOB) recovery method for P. ramorum, which requires collecting water from a source, baiting with healthy rhododendron leaves for a 3-day incubation period, followed by plating on semi-selective media. Rapid methods are needed for recovery and detection of P. ramorum propagules from water sources. Working at the National Ornamentals Research Site at Dominican University of California (NORS-DUC), we...

Native upland prairie and oak savanna habitats were once widespread in the Willamette Valley of western Oregon, but have been diminished by conversion to other land uses. These threatened habitats are considered essential for rare and endangered species such as the Fender’s blue butterfly. Restoring native upland prairie habitats is a major goal of wildland restoration in Oregon. The inadvertent spread of Phytophthora species from nurseries into native ecosystems can have long-term environmental and economic impacts, as has been seen with Phytophthora ramorum, P. lateralis, P. cinnamomi,...

The 2015 detection of the Phytophthora ramorum EU1 lineage in Oregon forests poses a new threat to sudden oak death management in Curry County. EU1 may be more aggressive and spread at a faster rate than has been observed for NA1 over the 17 years it has been managed in Oregon forests. EU1 may also infect some hosts, notably conifers, at a greater frequency. To assess any additional risk posed by EU1, we performed field surveys assessing the distribution and frequency of understory infection surrounding SOD-infested trees. We also conducted laboratory assays testing for epidemiologically...

Before Phytophthora ramorum was identified as the causal agent of sudden oak death in 2000, P. lateralis, cause of Port-Orford-Cedar root disease, was the only introduced Phytophthora that had been associated with widespread plant decline and mortality in California wildlands. The soil-borne P. lateralis is closely associated with riparian or high-rainfall sites with high soil moisture. In 2003, the well-known root pathogen P. cinnamomi was found to be causing extensive mortality of manzanita (Arctostaphylos myrtifolia, A vicida) in dry upland habitats of the lower Sierra Nevada foothills....

Forestry Commission England aerial surveillance operations to detect Phytophthora ramorum between 2009 and 2014 were primarily focused on identifying infected larch (Larix spp.), although sweet chestnut (Castanea sativa) has been recognized as a sporulating host of P. ramorum since the mid-2000s (Denman and others 2006). During follow-up ground investigations, infected sweet chestnut was confirmed and considered an incidental host on 23 sites (54 laboratory positives), with individual trees or small discrete stands of sweet chestnut affected but always in close proximity to other infected...

Studies of hybrid organisms often reveal two types of interspecific hybridization: polyploid hybridization, where the number of chromosomes changes during or immediately following hybridization, and homoploid hybridization, where the number of chromosomes is unchanged. Homoploid hybridization is thought to occur only between very closely-related species, while polyploidy can allow for the persistence of what would normally be a sterile or unstable cross between more distantly related species. Polyploid hybrids may not be able to interbreed with their parents, persisting through time as...

Within the large plant-pathogenic genus Phytophthora, lies an enigmatic phylogenetic cluster of five species known as “clade 3.” Conflicting studies have suggested that this group of species may be native to Europe or North America. At the turn of the 20th century, clade 3 was known only from a single species, P. ilicis, which had been isolated in North America and Europe. In 2002, a second species, P. psychrophila was described from declining European oak forests. In 2003, two additional species were introduced, with P. nemorosa found only in North America and P. pseudosyringae from both...

Araucaria araucana (Araucaria or monkey puzzle tree; Class = Pinopsida; Family = Araucariaceae) is an endangered conifer with a fragmented and relict distribution in southern Chile and Argentina. Araucaria is the type species of a genus of relatively old conifers with an ancient distribution that covered the continent of Gondwana, and that now comprises 19 extant species distributed in Oceania and South America. Araucaria has been historically threatened by logging (banned in 1990), wildfires, overgrazing, invasive trees, and extensive human harvesting of Araucaria seeds. More recently,...

In March 2015 Phytophthora ramorum was detected at The Bloedel Reserve, a 150 acre botanical garden in Kitsap County, WA. Infected plants were destroyed and the soil in an area surrounding these plants was steam-sterilized to a depth of 15 cm during the summer of 2015. An IPM program was developed in an effort to control the spread of P. ramorum and other Phytophthora species in the garden, reduce the risk of P. ramorum spread to the surrounding landscape, and minimize additional destruction of valuable plants and visual impacts to the garden. Several treatments were employed, including...

In 2018, we launched a pilot project, “Accreditation to Improve Restoration and Native Plant Nursery Stock Cleanliness (AIR)” to explore whether an audit-based accreditation program could be used to increase confidence that restoration and native plant nursery stock are not infected with Phytophthora species. Due to capacity and cost limitations, we accepted eleven nurseries in the greater San Francisco Bay Area in the initial phase. Each participating nursery completes a self-assessment to confirm that they are producing plants with the practices outlined in the Phytophthoras in Native...