Treesearch

One hundred eighty-seven sites were established in perennial watercourses and sampled for one to four years between 2004 and 2007 to monitor for the presence of Phytophthora ramorum throughout coastal central and northern California watersheds as well as portions of the Sierra Nevada mountain range. In 2007, 132 sites were monitored, including 65 new sites. The majority of the monitored watersheds have limited or no Pr at this time, but are near the epidemic range of P. ramorum and/or are considered high-risk for invasion by P. ramorum. Three currently infested watersheds in Sonoma,...

The proceeding worldwide spread and the expanding host spectrum of P. ramorum has become a serious threat to natural plant communities. To encounter this threat detailed knowledge about infection pathways and tissue colonization is essential. To analyze these issues, histological studies of infected tissue with epifluorescence microscopy have been started. For first infection tests Rhododendron has been taken as a model host. Root infection of potted Rhododendron cuttings with the P. ramorum isolate BBA 9/95 (ex-type strain) were started. Inoculation of the non injured plants was done by...

On behalf of the Fourth Phytophthoras in Forest and Natural Ecosystems local organizing committee and co-chairs Everett Hansen, Clive Brasier, and Giles Hardy, I thank you for your contributions to this Working Party meeting. The past week has stimulated much thought and discussion, thanks to the 100 participants from 15 countries, 48 papers and 31 posters, two field trips, and two evening overview sessions.

Four Phytophthora species have recently been described in California natural ecosystems: Phytophthora ramorum, P. ilicis, P. pseudosyringae, and P. cinnamomi. The first three species are of recent description, while the last one is a well-known pathogen associated with agricultural crops in the Western USA and in many areas world-wide. P. ramorum and P. cinnamomi are both causing significant mortality in native California hosts, while the other two species are associated with limited mortality of affected plant hosts. We have used both AFLP and microsatellite analyses to unravel the...

The recent epidemics of sudden oak death, caused by Phytophthora ramorum, in the coastal forests of California and southwest Oregon have drawn attention to other species of Phytophthora present in natural ecosystems that may threaten forest tree health. Since Phytophthora species are well adapted to aquatic environments, the species present in a strategically-selected stream may represent the occurrence and distribution of Phytophthora species over the relatively large land area drained by this stream. Based on this assumption, five streams in three watersheds in the Pisgah National Forest...

Long-term storage of cultures of Phytophthora species is a challenge for any lab managing a working collection of isolates. Storage in liquid nitrogen is generally considered to be optimal for archival storage, and successful recovery of most species is regularly achieved after many years. Nitrogen storage has its drawbacks, however, especially for a working collection. It requires species specific freezing conditions, and thawing must be done carefully. Equipment is bulky, and regular addition of liquid nitrogen is necessary. Storage in vials in water at room temperature is an efficient,...

Austrocedrus chilensis, an indigenous Cupressaceae of the Patagonian Andes forests, is suffering a disease that has been called "Mal del Ciprés" (MDC). This disease was first reported more than 50 years ago but, in spite of many studies, its causes remained unclear until recently. The disease begins in the root system, the distribution and pattern of spread of mortality in a stand is consistent with a soil-borne pathogen, and it is associated with seasonally poorly drained soils. Symptoms include defoliation, basal resinous exudates and red-brown necrotic lesions in the inner bark extending...

We investigated the seasonal patterns of soil phosphorus (P) fractions under five vegetation types – Ulmus macrocarpa savanna, grassland, Pinus sylvestris var. mongolica plantation, Pinus tabulaeformis plantation, and Populus simonii plantation – in the southeastern Keerqin Sandy Lands of China. The measured P fractions (0–20 cm depth) included: soil total P (TP), total organic and inorganic P (TPo and TPi), bicarbonate extractable organic and inorganic P (BPo and BPi), microbial biomass P (MBP), and in situ resin-adsorbed P (resin-P). Soil TP and TPo concentrations in the savanna and...

Phytophthora taxon Pg chlamydo is perhaps the second most abundant Phytophthora species in the world, after P. gonapodyides, although it is commonly misidentified. Pg chlamydo is frequently encountered in streams and rivers in western North America, Argentina, China, and Europe. It has occasionally been recovered from forest soil and was once isolated from a bole canker on a tanoak tree; it was pathogenic to tanoak in artificial inoculation. Pg chlamydo resembles P. gonapodyides in culture, and is related to that species. It is apparently sterile, not itself forming sexual structures even...

Phytophthora ramorum was first discovered in Southwest Oregon forests in 2001, where it was killing tanoak (Lithocarpus densiflorus) and infecting Pacific rhododendron (Rhododendron macrophyllum) and evergreen huckleberry (Vaccinium ovatum). At that time there were nine infested forest sites totaling 16 ha. Aerial photographs suggest that P. ramorum probably was killing tanoak trees at one of these sites as early as 1998. In fall of 2001 eradication of the pathogen from infested sites began by cutting, piling and burning infected plants and all host vegetation within 30 to 100 m. of...