Treesearch

The Presidio, a 1,500 acre National Park on a former military post at the foot of the Golden Gate Bridge, is a major outdoor and cultural recreation hub in northwest San Francisco. As part of the Golden Gate National Recreation Area, it is among the most visited urban national parks, but also home to twelve species of rare, threatened or endangered plants, many associated with serpentine soils, as well as habitat for over 300 bird species and other wildlife. In 2015, the Presidio initiated a Phytophthora management program to protect endangered plant species and native habitat. Dieback...

Although sudden oak death has been the primary concern for California oak woodlands over the last 20 years, other fungal pathogens of oak (Quercus spp.), California bay (Umbellularia californica), and tanoak (Notholithocarpus densiflorus) also occur in California. Many cosmopolitan Botryosphaeriaceae species with wide host ranges can invade oak and tanoak under stress conditions through wounds, causing perennial cankers in twigs and shoots and large bole cankers. Oak root rot caused by Armillaria mellea is widespread in native California soils and infected trees often exhibit cambium death...

Ecological disturbances have clear potential to shape the dynamics of native and introduced plant diseases, via their impacts on the spatial pattern of hosts, host composition, pathogen survival, and microclimatic conditions. Yet, studies examining potential interactions between disease and disturbance are rare, or primarily focus on pathogen occurrence, rather than the additional processes of spread, infection, and host mortality that determine disease impacts. Given that anthropogenic activities have both altered disturbance regimes across the western United States and introduced...

Root rots caused by exotic Phytophthora species have been associated with dying and declining vegetation in multiple native plant communities in the San Francisco Bay Area and elsewhere in northern California. This project focused on detecting Phytophthora species that are currently affecting or have the potential to seriously affect populations of covered plants in the Santa Clara Valley Habitat Conservation Plan/Natural Community Conservation Plan (HCP/NCCP) area (Swiecki and Bernhardt 2018). A key component of the Santa Clara Valley HCP/NCCP is the creation of an 18,800 ha reserve...

This study describes the identification of several Phytophthora species previously found in San Francisco Bay Area nurseries (Sims and others 2018a) from multiple sites at the urban wildland interface within the greater San Francisco Bay Area. Isolation success was highest from the three plant species: Diplacus aurantiacus (sticky monkey-flower), Ceanothus thyrsiflorus (blueblossum), and Frangula californica (California coffeeberry), growing in restoration sites and in adjacent disturbed sites. Isolation success was zero in control undisturbed “natural” areas adjacent to infested sites. In...

Phytophthora diseases in landscapes have gained prominence during the 21st century, due to an increase in Phytophthora surveys and a greater focus on species-level diagnostics. Concurrently, the number of known Phytophthora species has increased from about 60 in 1996 to more than 300 today. In addition to entirely novel species being discovered, many of the most common and well-known 20th century species have been revealed to represent species complexes and are rapidly being divided into new taxa. Beyond the increasingly large Phytophthora, two Phytophthora-like related genera, Calycofera...

The Angeles National Forest (ANF), located in the greater Los Angeles metropolitan area encompasses approximately 700,000 acres (238,230 ha), comprising a vital biodiversity hot spot. From 2002 to 2008, the ANF was affected by three major fires, the Copper (2002), Ranch (2007) and Sayre (2008). Together, these fires affected approximately 40,000 acres (16,187 ha) of coastal sage scrub, montane chaparral, grassland, riparian corridor, as well as isolated big cone Douglas-fir (Pseudotsuga macrocarpa) stands. Droughts and floods in the subsequent years, plus off-highway vehicle use, aggravated...

The metabarcoding approach has revolutionized the study of microbial ecology with its ability to detect microbial DNA at an unprecedented depth and coverage. This method exploits highthroughput sequencing and DNA barcoding for identification of microbial species, including novel and uncultivable microbes. The metabarcoding approach is gaining more interest by the Phytophthora scientific community for monitoring the existence and spread of Phytophthora species in diverse habitats. Understanding and mitigating metabarcoding limitations is crucial for achieving better resolution and accurate...

The inadvertent spread of Phytophthora species from nurseries into native ecosystems has increased interest in assessing Phytophthora diversity in native plant communities. Of major concern is the inadvertent movement of Phytophthora spp. from native plant nurseries into vulnerable habitats during restoration outplantings. Root-infecting Phytophthora spp. are abundant within plant nurseries; their introduction can result in failed plantings and further spread of Phytophthora into surrounding habitat. To assess Phytophthora diversity, we surveyed restoration sites within the Midpeninsula...

Soil solarization is a low-cost, non-chemical method that can be highly effective in killing soilborne Phytophthora species in infested nurseries. This method consists of using a transparent plastic film to trap solar radiant heat. Understanding and implementing the best methods for soil solarization are critical for successful eradication of pathogens. We examined how the size of the solarization treatment area, soil moisture content, and duration of solarization affected the survival of Phytophthora inocula buried at 5, 15, and 30 cm. Research sites were established in Corvallis, OR and...