Treesearch

The use of stream monitoring is an important method for early detection of Phytophthora ramorum. Five different waterway locations representing different ecosystems and potential P. ramorum inoculum sources across southern Louisiana were monitored for P. ramorum using bait bags containing whole Rhododendron 'Cunningham's White' leaves from December 2010 to January 2011. After 1 week, the leaves were retrieved and 30 leaf disks (11 mm diameter) per bait bag were taken from necrotic areas of the exposed leaves and placed on a Phytophthora-selective agar medium (PARPH+V8) or 2 percent water...

Phytophthora ramorum characteristically produces large amounts of chlamydospores in vitro, but the role of these propagules in the disease cycle remains unclear. Germination is difficult to observe and quantify if chlamydospores are not free of mycelium, and the low frequency of germination commonly reported suggests that requirements for germination may not have been entirely met. Here, we conducted germination experiments factoring for chlamydospore age, chlamydospore isolation method, and nutrient medium. Chlamydospore germination frequency in each of the treatments ranged from 0 to 70...

In southwest Oregon, an aggressive program of cutting and burning host plants in an effort toeradicate Phytophthora ramorum was initiated. It was soon apparent that tanoak (Notholithocarpus densiflorus (Hook.& Arn.) Manos, Cannon& S.H. Oh) resprouts were highly susceptible to P. ramorum and that infected sprouts hamper eradication efforts by maintaining inoculum on site (Hansen and Sutton 2006). The basidiomycete fungus, Chondrostereum purpureum causes a white rot of mostly broadleaf trees and has a wide host range. It invades through fresh wounds in the xylem or cut stumps and is a weak...

Phytophthora ramorum has continued to spread in forests in the western United States, the United Kingdom, and the Republic of Ireland, and continues to challenge vegetation and ecosystems in temperate regions (Brasier and Webber 2010, Grünwald et al. 2012). Disease management in the wild has been applied with some success in localized outbreaks in northern California and in Oregon, and in trial treatments; for example, using host removal and host protection (phosphonate application) at plot and stand levels. However, there is still very limited observational data on the efficacy of these...

In late August 2009, a 20.3 cm (8 in) diameter tanoak (Notholithocarpus densiflorus (Hook. & Arn.) Manos, Cannon & S.H. Oh) adjacent to a popular hiking trail on the Rogue River-Siskiyou National Forest was found infected with Phytophthora ramorum. The trail was immediately closed to the public. An eradication treatment consisting of injecting herbicide and cutting, piling, and burning tanoaks and other selected hosts in a 91.4 m (300 ft) radius around the infected tanoak was prescribed and completed by early winter. Close to 487.7 m (1600 ft) of trail lies within or on the boundary of the...

Application of phosphonate compounds has been shown to be an effective preventive treatment for sudden oak death (SOD), caused by Phytophthora ramorum, in coast live oak (Quercus agrifolia Née) and tanoak (Notholithocarpus densiflorus Manos, Cannon & S.H. Oh). To test the effectiveness of these treatments in a natural setting, paired 400 m2 sections of mixed evergreen/tanoak stands were randomly designated as either treatment or control plots, and topically treated with Agri-Fos® systemic fungicide. The experiment included 36 field plots in six California counties, including nearly 700...

In 2005, eight 50 x 50 m plots, all with a significant component of California bay laurel (Umbellularia californica (Hook. & Arn.) Nutt.), were selected in the Soquel Demonstration State Forest, Santa Cruz County, California. Each plot contained a 5 m buffer zone around the edges and sixteen 10 x 10 m squares. A bucket was placed at the center of each square: buckets were filled with at least 5 L of water every 2 to 3 weeks, and five California bay laurel leaves were placed as bait in each bucket for 2- to 3-week periods throughout the year (or when leaf infection was ascertained to...

Beh, Maia M.; Metz, Margaret; Seybold, Steven J.; Rizzo, David. 2013. The novel interaction between Phytophthora ramorum and wildfire elicits elevated ambrosia beetle landing rates on tanoak. In: Frankel, S.J.; Kliejunas, J.T.; Palmieri, K.M.; Alexander, J.M. tech. coords. Proceedings of the sudden oak death fifth science symposium. Gen. Tech. Rep. PSW-GTR-243. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: p. 123.

The focus of our research efforts has been to develop methods to quickly identify plants, soil, and water samples infested with Phytophthora spp., and to rapidly confirm the findings using novel isothermal DNA technologies suitable for field use. These efforts have led to the development of a rapid Immunostrip® that reliably detects virtually all strains of Phytophthora spp. in plant, soil, and water samples within minutes. Two formats of a rapid molecular method were developed to accurately confirm the results. These methods are able to specifically identify P. ramorum in crude extracts...

Of concern for disease management and certification programs in nursery ornamentals is that roots, when colonized by Phytophthora ramorum, may serve as a potential reservoir of inoculum. An additional complication is that the above ground portion of plants with root infections may be asymptomatic. Our central hypothesis is that mild abiotic stresses can compromise basic host resistance to trigger systemic development of disease from soilborne infections. Corollary to this is that these stresses may also influence the efficacy of chemical management.