Treesearch

We conducted four experiments to evaluate the effectiveness of phosphonate application to tanoak (Notholithocarpus densiflorus (Hook. & Arn.) Manos, Cannon & S.H.Oh) forests in south-western Oregon: (1) aerial application to forest stands; (2) trunk injection; (3) foliar spray of potted seedlings; and (4) foliar spray of stump sprouts. We compared aerial spray treatments: (1) no treatment (unsprayed); (2) low-dose (17.35 kg a.i. ha-1); and (3) high dose (34.5 kg a.i. ha-1), applied by helicopter in a carrier volume of 188 L ha-1 to 4-ha treatment plots. Treatments were applied in November...

The phytopathogen Phytophthora ramorum (Werres, DeCock & Man in't Veld), causal agent of Sudden Oak Death (SOD) of oaks (Quercus spp.) and tanoaks (Notholithocarpus densiflorus syn. Lithocarpus densiflorus), is established in coastal forests of the western United States. Since the discovery of SOD in the Douglas-fir / tanoak forests of southwest Oregon in 2001, a multiagency effort has ensued with the goal of fully eliminating P. ramorum from this originally small and isolated area. In this study we investigated the epidemiology of SOD in Oregon, particularly as it affects the success of...

Since the discovery of Phytophthora ramorum Werres, De Cock & Man In't Veld in south-western Oregon forests in 2001, newly infected areas are detected each year. Yet, there are still gaps in our knowledge about how the pathogen spreads or where new infections come from. Our study aims to track the spread of P. ramorum in Oregon forests and within individual trees using DNA fingerprinting. We examined the genetic diversity of 1589 samples collected from 2001 to 2008 on several temporal and spatial scales. We identified 60 novel multilocus genotypes (MGs# with 9 to 44 MGs found in each year....

Phytophthora siskiyouensis Reeser & E.M. Hansen (2007) was discovered first in streams and soil in Curry County, Oregon in areas dominated by native forest, and most isolates continue to come from these sources. Only later, and still infrequently, were isolates of the new species recovered from diseased forest plants. Recent reports that the same fungus was killing alders planted in cities in California (Rooney-Latham et al. 2007)and Australia (Smith et al. 2006) were a surprise. Phytophthora siskiyouensis appears to be part of the native forest mycoflora of SW Oregon, causing occasional...

P. ramorum Werres, De Cock, & Man in't Veld (2001) appears to be an exotic species introduced from an unknown origin to Europe and western N. America in the mid-1990s, likely on nursery plants (Mascheretti et al. 2008). In California and southwest Oregon, the pathogen spread to native oak and tanoak forests, where it causes lethal stem cankers ('sudden oak death&339;). More than a million trees have been killed (Meentemeyer et al. 2011). In Europe, where nurseries in over 20 countries reported P. ramorum, the disease on trees was limited to isolated stands of beech and oak associated with...

Phytophthora lateralis was named by Tucker and Milbrath in 1942. There are no known synonyms. P. lateralis was classified in morphological group V by Stamps et al. (1990); the group includes homothallic species with paragynous antheridia and nonpapillate, proliferating sporangia.

Phytophthora austrocedrae Gresl. & E.M. Hansen (2007) was isolated from necrotic lesions of stem and roots of Austrocedrus chilensis (Cupressaceae). It is homothallic with semi-papillate sporangia, oogonia with amphigynous antheridia, and very slow growth. It is the cause of "mal del cipreés", a lethal disease of Austrocedrus in Argentina. Austrocedrus chilensis (cipreés de la cordillera) is endemic to southern Argentina and Chile. It is the most widely distributed tree species of the few conifers inhabiting the slopes of the Andes Mountains in Patagonia. [partial funding through FS grant...

A rainfall interception study was conducted in Oakland, California to determine the partitioning of rainfall and the chemical composition of precipitation, throughfall, and stemflow. Rainfall interception measurements were conducted on a gingko (Ginkgo biloba) (13.5 m tall deciduous tree), sweet gum (Liquidambar styraciflua) (8.8 m tall deciduous), and lemon tree (Citrus limon) (2.9 m tall broadleaf evergreen). The lemon, ginkgo, and sweet gum intercepted 27.0%, 25.2% and 14.3% of gross precipitation, respectively. The lemon tree was most effective because it retained its foliage year-round...

Mediterranean ecosystems are hotspots of biodiversity. Because of a coincidence of high species richness and human presence, Mediterranean biodiversity is particularly threatened by processes such as habitat degradation, fragmentation and loss, pollution, climate change and introduction of invasive species. Invasive tree pathogens are among the problematic exotic species of California, Chile, the Mediterranean, South Africa and Australia. In this review, we provide an update on a selection of non-native tree pathogens currently posing a threat in Mediterranean ecosystems. The impact of...

Disease ecology has made important steps in describing how epidemiological processes control the impact of pathogens on populations and communities but fewer field or theoretical studies address disease effects at the ecosystem level. We demonstrate that the same epidemiological mechanisms drive disease intensity and coarse woody debris (CWD) dynamics in natural forest ecosystems impacted by an emerging disease. Sudden oak death (causal agent, Phytophthora ramorum) has caused mortality of tanoak (Notholithocarpus densiflorus) on a spatial scale and rate comparable to other major North...