Treesearch

Coast redwood (Sequoia sempervirens) frequently grows in association with tanoak (Lithocarpus densiflorus) along the central and northern California coast. High rates of tanoak mortality beginning in the mid 1990’s have been attributed to Phytophthora ramorum, a water mold believed to be non-native. Of the many species that host P. ramorum, tanoak is one of the most susceptible and thousands of tanoak trees have died in the past ten years. In a two species forest, the implications of losing one species may be severe, especially when one species is a mast producer such as tanoak. These...

Sudden oak death (SOD) is a tree disease caused by a recently described pathogen, Phytophthora ramorum. The disease affects dozens of plant species, but its effects are particularly pronounced in stands of coast live oak (Quercus agrifolia), often resulting in large stands with dead canopies and many downed trees. Such disease-induced habitat changes may impact bird populations both directly and indirectly. For example, forest dieback can result in changes to insect populations, which subsequently impact insectivorous birds by forcing them to switch prey items, change foraging substrates,...

Although tanoak (Lithocarpus densiflorus) acorns are a valuable source of food for many species of wildlife few data on tanoak acorn production exist. We conducted studies of acorn production in tanoaks to understand the potential impact of Phytophthora ramorum on acorn availability to wildlife. In 2002 we established 3-ha seed-trap grids in redwood-tanoak habitat to estimate acorn production at the stand level. We established one grid in Pfeiffer Big Sur State Park (PBS), where P. ramorum has caused high levels of tanoak morbidity and mortality, and another in the Landels-Hill Big Creek...

Within San Luis Obispo County, California, coast live oak (Quercus agrifolia) woodlands provide important habitat for many wildlife species (see Tietje and others, this volume). Unfortunately, many of these woodlands are at high risk of sudden oak death (SOD) infection should the pathogen (Phytophthora ramorum) become established in the County (Meentemeyer and others 2004). To assess the potential impacts of SOD on the small mammal and herpetofaunal communities in this high-risk habitat, we surveyed for these taxa at three separate high-risk study sites within the County. We considered the...

The effectiveness of 20 systemic and contact fungicides in protecting Douglas-fir seedlings from infection by Phytophthora ramorum was determined. Some systemic products were applied about a week prior to bud break, while most treatments were applied just after bud break. In addition to the fungicides, two surfactants were included in the post-bud break application tests. One day after the post-bud break treatment applications, all the seedlings were inoculated by spraying seedlings with zoospore suspensions obtained from isolates of A1 and A2 mating types of P. ramorum. Inoculated...

Commercial rhododendron plants have been the most important hosts of Phytophthora ramorum in Europe. As part of the European Union (EU) emergency phytosanitary measures 2002/757/EU and 2004/426/EU all commercial rhododendron-growing premises are surveyed for P. ramorum. Detection of P. ramorum leads to quarantine measures, including destruction of plants, and could lead to considerable financial damage for the companies involved. Growers are taking all possible measures to avoid P. ramorum including preventive fungicide treatments. However, because little information is available on the...

In Oregon, tanoak (Lithocarpus densiflorus) is the tree species most susceptible to Phytophthora ramorum, and Sudden Oak Death (SOD) occurs only in forests where tanoak is present. Oregon is attempting to eradicate the pathogen by complete destruction of host plants in and near infested sites. Although the eradication effort has been successful to a degree, it is clear that we need other tools to limit spread of the pathogen in forests. The purpose of this study is to begin evaluating phosphonate (Agrifos-400®) treatments as tools for managing SOD in Oregon Forests. Phosphonate (Agrifos-400...

Determining how Phytophthora ramorum is dispersed across the landscape is critical for understanding the ecology and epidemiology of this influential pathogen. To date, researchers have shown that abiotic factors – such as rain-splash, wind-blown rain and down-stream transport of inoculum – are critical mechanisms for the dispersal of this pathogen. In contrast, little research has focused on the potential for human dispersal of P. ramorum, although work on other pathogens – such as P. lateralis attacking Port Orford cedar – suggests that humans can play an influential role in disease...

Little is known about the potential short- and long-term impacts of sudden oak death (SOD) on forest structure and composition. This study began in 2002 to evaluate the effects of SOD on coast live oak (Quercus agrifolia) - California bay laurel (Umbellularia californica) forests over a gradient of Phytophthora ramorum infection. In order to evaluate stand level impacts of the disease, we present mortality data from three time periods: recent past (five to 10 years before 2002), present (2002-2004), and future (next five years). Because large numbers of recently downed stems (mainly Q....

Fire is often integral to forest ecology and can affect forest disease dynamics. Sudden oak death has spread across a large, fire-prone portion of California, killing large numbers of oaks and tanoaks and infecting most associated woody plants. Building on our earlier study of fire-disease dynamics, we examined spatial patterns of confirmed infections in relation to past fire history for a single county using a geographic information system (GIS). The region analyzed here is Sonoma County, where infections have been documented in past burn areas and exposure to the disease is thought to be...