Treesearch

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.

The primary foliar host for Phytophthora ramorum is California bay laurel, Umbellularia californica (Hook. & Arn.) Nutt., a main reservoir for the pathogen in California woodlands. We investigated environmental and pathogen-mediated influences on incidence and severity of P. ramorum infection of U. californica, as well as developing non-destructive means for controlling P. ramorum in woodlands.

The Big Sur region of central California is a rugged, fire-prone area that has been severely affected by Phytophthora ramorum. Meentemeyer et al. (2008) estimated that over 200,000 oaks and tanoaks had been killed by P. ramorum across the Big Sur ecoregion by 2005. In June of 2008, a complex of lightning-initiated fires burned over 95,000 ha in Big Sur, including 43 percent of our long-term network of disease monitoring plots. Here we compile data collected in these plots before the fire in 2006 and 2007 (Metz et al. 2011), with 3 consecutive years of data following the fire (2009 through...

To determine if either herbaceous or woody plants are more competitive with longleaf pine (Pinus palustris Mill.) trees, four vegetation management treatments— check, herbaceous plant control (HPC), woody plant control (WPC), and HPC+WPC—were applied in newly established longleaf pine plantings in a randomized complete block design in two studies. Prescribed fire was repeatedly applied across both study sites, and pine measurements were continued for 12 years. Pine survival was not significantly different among the four treatments in either study. In Study 1, pines were taller on HPC+WPC...

Germination of chlamydospores is difficult to accurately assess when chlamydospores are attached to remnants of supporting hyphae. We developed two approaches for closely observing and rigorously quantifying the frequency of chlamydospore germination in vitro. The plate marking and scanning method was useful for quantifying germination of large numbers of chlamydospores over a 7-day period. A method involving time lapse photography of microscope slide cultures was effective for visualizing the process of germination over shorter time periods.

In California, wildland hosts that support sporulation of Phytophthora ramorum, such as California bay laurel (Umbellularia californica (Hook. & Arn.) Nutt.) and tanoak (Notholithocarpus densiflorus (Hook. & Arn.) Manos, Cannon & S.H. Oh), also develop prolific basal sprouts following mortality, injury, or tree harvest. Assessing long-term silvicultural treatment effectiveness for P. ramorum control is complicated by this stimulation of basal sprouting following tree removals. To better design P. ramorum treatments, we need to know how sprouts regenerating from cut host tree stumps are...

We are working to evaluate risks associated with human spread of the sudden oak death (SOD) pathogen, Phytophthora ramorum, to currently uninfested areas in California. Port-Orford-cedar (Chamaecyparis lawsoniana (A. Murray) Parl.) root disease (POC RD), caused by Phytophthora lateralis, has brought awareness that pathogens can be moved in forest settings by materials adherent to vehicles and equipment. Discovery of this human vector prompted P. lateralis control measures with notable social and economic costs, such as road closures, vehicle and equipment washing requirements, and standards...

Phytophthora ramorum, the cause of sudden oak death, was first discovered in Oregon forests in July 2001. An aggressive eradication treatment program was immediately put into place on all lands where it was found. Eradication treatments have changed over time as we have learned more about pathogen behavior. Treatment prescriptions currently consist of cutting and burning infected and exposed host plants, and where possible, injecting herbicide into tanoaks to prevent sprouting. The effort has slowed, but not stopped, long-distance dispersal of the pathogen.