scholarly journals Improved detection and identification of the sudden oak death pathogen Phytophthora ramorum and the Port Orford cedar root pathogen Phytophthora lateralis

2019 ◽  
Vol 68 (5) ◽  
pp. 878-888 ◽  
Author(s):  
N. Feau ◽  
D. I. Ojeda ◽  
S. Beauseigle ◽  
G. J. Bilodeau ◽  
A. Brar ◽  
...  
Keyword(s):  
Phytophthora Ramorum ◽  
Sudden Oak Death ◽  
Root Pathogen ◽  
Detection And Identification ◽  
Phytophthora Lateralis ◽  
Port Orford Cedar

scholarly journals Susceptibility of Pacific Yew to Phytophthora lateralis

Plant Disease ◽  
1997 ◽  
Vol 81 (12) ◽  
pp. 1400-1404 ◽  
Author(s):  
Marion S. Murray ◽  
Everett M. Hansen
Keyword(s):  
Root Colonization ◽  
Field Survey ◽  
Root Hairs ◽  
Lesion Length ◽  
New Host ◽  
Root Pathogen ◽  
Phytophthora Lateralis ◽  
Southwest Oregon ◽  
Port Orford Cedar

In 1991, Pacific yew was reported as a new host for Phytophthora lateralis, an aggressive root pathogen thought previously to be specific to Port Orford cedar. This study was designed to compare the pathogenicity of P. lateralis on the two hosts through seedling, stem, branch, and rootlet inoculations, and field survey. Mortality of inoculated plants averaged 72% for cedar and 4% for Pacific yew, and root colonization by P. lateralis was significantly greater in cedar seedlings than in Pacific yew seedlings. Lesion length on the cedar seedling stems was twice the lesion length on Pacific yew stems, and cedar branches had lesions four times longer than Pacific yew branches. Abundant zoospore aggregation occurred on cedar rootlets along the zone of elongation and the region of maturation. In comparison, far fewer zoospores encysted on Pacific yew rootlets, and they were concentrated on the root hairs. A field survey along 0.8-km stretches of three infested streams in southwest Oregon and northwest California revealed a total of 1,199 dead Port Orford cedar (46% mortality), and 86 dead Pacific yew (10% mortality). We conclude that Pacific yew is less susceptible to P. lateralis than Port Orford cedar.

Forest transformation resulting from an exotic pathogen: regeneration and tanoak mortality in coast redwood stands affected by sudden oak death

2011 ◽  
Vol 41 (4) ◽  
pp. 763-772 ◽  
Author(s):  
Benjamin S. Ramage ◽  
Kevin L. O’Hara ◽  
Alison B. Forrestel
Keyword(s):  
Canopy Cover ◽  
Phytophthora Ramorum ◽  
Sudden Oak Death ◽  
Coast Redwood ◽  
Marin County ◽  
Wildlife Species ◽  
Management Interventions ◽  
Redwood Forests ◽  
Exotic Pathogen ◽  
Notholithocarpus Densiflorus

Sudden oak death is dramatically altering forests throughout coastal California, but little is known about the communities that are assembling in affected areas. This emerging disease, caused by the exotic pathogen Phytophthora ramorum (S. Werres, A.W.A.M. de Cock), has had especially severe effects on tanoak ( Notholithocarpus densiflorus (Hook. & Arn.) Manos, Cannon & S.H. Oh), a broadleaf evergreen that is abundant in forests dominated by coast redwood ( Sequoia sempervirens (D.Don) Endl.). Tanoak, a valuable food source to numerous wildlife species, is unlikely to successfully regenerate in diseased areas, and thus, affected redwood forests are transitioning to a novel state. In this study, to predict which species might replace tanoak, we investigated regeneration patterns in heavily impacted stands in Marin County, California. Our main findings were as follows: (i) despite reductions in canopy cover, there is no evidence that any species other than tanoak has exhibited a regenerative response to tanoak mortality, (ii) the regeneration stratum was dominated by redwood and tanoak (other tree species were patchy and (or) scarce), and (iii) some severely affected areas lacked sufficient regeneration to fully re-occupy available growing space. Our results indicate that redwood is likely to initially re-occupy the majority of the ground relinquished by tanoak, but also provide evidence that longer-term trajectories are unresolved, and may be highly responsive to management interventions.

scholarly journals Disease on Nursery Stock as Affected by Environmental Factors and Seasonal Inoculum Levels of Phytophthora ramorum in Stream Water Used for Irrigation

Plant Disease ◽  
2008 ◽  
Vol 92 (11) ◽  
pp. 1566-1573 ◽  
Author(s):  
S. A. Tjosvold ◽  
D. L. Chambers ◽  
S. T. Koike ◽  
S. R. Mori
Keyword(s):  
Stream Water ◽  
Disease Incidence ◽  
Phytophthora Ramorum ◽  
Sudden Oak Death ◽  
Nursery Stock ◽  
Stream Sampling ◽  
Flow Through ◽  
High Concentrations ◽  
Electronic Sensors ◽  
Native Host

A pear bait monitoring system was used to detect and quantify Phytophthora ramorum propagules in streams that flow through woodland areas with sudden oak death in Santa Cruz County, CA from 2001 to 2007. Stream propagules were detected most frequently or occurred in highest concentrations in winter and spring. The stream propagule concentration was characterized with statistical models using temperature and rainfall variables from 2004 to 2007. The highest concentrations of propagules occurred when stream sampling was preceded by about 2 months with low maximum daily temperatures and by 4 days with high rainfall. The occurrence of propagules in streams in the summer was mostly associated with infected leaves from the native host Umbellaria californica that prematurely abscised and fell into the water. When the stream water was used for irrigating rhododendron nursery stock from 2004 to 2007, disease occurred only three times in the two wettest springs (2005 and 2006) on plants sprinkler irrigated with stream water with relatively high concentrations of propagules. Disease incidence was described with a statistical model using the concentration of infective propagules as measured by pear baiting and consecutive hours of leaf wetness measured by electronic sensors at rhododendron height. The concentration of infective propagules was significantly reduced after water was pumped from the stream and applied through sprinklers.

Citizen Science Uncovers Phytophthora ramorum as a Threat to Several Rare or Endangered California Manzanita Species

Plant Disease ◽  
2020 ◽  
Vol 104 (12) ◽  
pp. 3173-3182
Author(s):  
Matteo Garbelotto ◽  
Tina Popenuck ◽  
Brett Hall ◽  
Wolfgang Schweigkofler ◽  
Francesco Dovana ◽  
...  
Keyword(s):  
Phytophthora Ramorum ◽  
Sudden Oak Death ◽  
Santa Cruz ◽  
Forest Disease ◽  
Marin County ◽  
Interspecific Differences ◽  
Detached Leaves ◽  
Comparative Susceptibility ◽  
The University ◽  
First Time

The Sudden Oak Death (SOD) Blitzes consist of yearly surveys led by citizen scientists designed to map the distribution of Phytophthora ramorum, cause of the forest disease called SOD, across northern California. During the 2017 Santa Cruz County SOD Blitz, six rare or endangered Arctostaphylos (manzanita) species were found to be possibly symptomatic for the first time. Symptoms included branch cankers and associated canopy mortality, and affected multiple individuals per species. Isolates of P. ramorum were obtained from each of the six species and, through a 30-day-long inoculation experiment on live plants, Koch’s postulates were completed for each one of them, conclusively determining that they all are hosts of this pathogen. Two additional manzanita species were later found to be apparently symptomatic in Marin County. Inoculations on detached branches using an isolate of P. ramorum obtained from one of the six rare species from Santa Cruz County were successful, suggesting that these two species may also be hosts of P. ramorum. Detached leaves of all eight species were also successfully inoculated at the University of California-Berkeley in fall 2018 and then again in spring 2019. In these cases, the same isolate was used for all inoculations, in order to obtain information on the comparative susceptibility of the eight species in question. Both branch and leaf inoculations identified significant interspecific differences in susceptibility. The production of sporangia was low on all species but it was not zero, suggesting that sporulation may cause within-plant and limited across-plant contagion, especially in rainy years.

Novel introductions and epidemic dynamics of the sudden oak death pathogen Phytophthora ramorum in Oregon forests

2020 ◽  
Author(s):  
Nicholas C Carleson ◽  
Hazel Daniels ◽  
Paul Reeser ◽  
Alan Kanaskie ◽  
Sarah Navarro ◽  
...  
Keyword(s):  
Principal Component Analysis ◽  
Population Dynamics ◽  
Microsatellite Loci ◽  
Forest Ecosystems ◽  
Principal Component ◽  
Phytophthora Ramorum ◽  
Sudden Oak Death ◽  
Clonal Lineage ◽  
Epidemic Dynamics ◽  
One Year

Sudden oak death caused by Phytophthora ramorum has been actively managed in Oregon since the early 2000’s. To date, this epidemic has been driven mostly by the NA1 clonal lineage of P. ramorum, but an outbreak of the EU1 lineage has recently emerged. Here we contrast the population dynamics of the NA1 outbreak first reported in 2001 to the outbreak of the EU1 lineage first detected in 2015. We tested if any of the lineages were introduced more than once. Infested regions of the forest were sampled between 2013-2018 (n = 903) and strains were genotyped at 15 microsatellite loci. Most genotypes observed were transient, with 272 of 358 unique genotypes emerging one year and disappearing the next. Diversity of EU1 was very low and isolates were spatially clustered (< 8 km apart), suggesting a single EU1 introduction. Some forest isolates are genetically similar to isolates collected from a local nursery in 2012, suggesting introduction of EU1 from this nursery or simultaneous introduction to both the nursery and latently into the forest. In contrast, the older NA1 populations were more polymorphic and spread over 30 km2. Principal component analysis supported two to four independent NA1 introductions. The NA1 and EU1 epidemics infest the same area but show disparate demographics owing to initial introductions of the lineages spaced 10 years apart. Comparing these epidemics provides novel insights into patterns of emergence of clonal pathogens in forest ecosystems.

scholarly journals Root Rot of Juniperus and Microbiota by Phytophthora lateralis in Oregon Horticultural Nurseries

Plant Disease ◽  
2020 ◽  
Vol 104 (5) ◽  
pp. 1500-1506
Author(s):  
Ebba K. Peterson ◽  
Franziska Rupp ◽  
Joyce Eberhart ◽  
Jennifer L. Parke
Keyword(s):  
Root Rot ◽  
Internal Transcribed Spacer ◽  
Major Gene ◽  
Resistance Breeding ◽  
Its2 Region ◽  
Phytophthora Spp ◽  
Major Gene Resistance ◽  
Phytophthora Lateralis ◽  
Chamaecyparis Lawsoniana ◽  
Port Orford Cedar

Widespread symptoms of root rot and mortality on Juniperus communis and Microbiota decussata were observed in two horticultural nurseries in Oregon, leading to the isolation of a Phytophthora sp. from diseased roots. Based on morphology and sequencing the internal transcribed spacer ITS1-5.8S-ITS2 region, isolates were identified as the invasive pathogen Phytophthora lateralis, causal agent of Port-Orford-cedar (POC; Chamaecyparis lawsoniana) root disease. Additional sequencing of the cytochrome c oxidase subunit 1 and 2 genes identified all isolates as belonging to the PNW lineage. Utilizing recovered isolates plus a POC-wildlands isolate and susceptible POC as controls, we completed Koch’s postulates on potted Juniperus and Microbiota plants. Nursery isolates were more aggressive than the forest isolate, which was used in the POC resistance breeding program. Increased aggressiveness was confirmed using a branch stem dip assay with four POC clones that differed in resistance, although no isolate completely overcame major-gene resistance. Isolates were sensitive to mefenoxam, a fungicide commonly used to suppress Phytophthora spp. growth in commercial nurseries. Although POC resistance is durable against these more aggressive nursery isolates, the expanded host range of P. lateralis challenges POC conservation through the continued movement of P. lateralis by the nursery industry.

Phytophthora ramorum, the cause of sudden oak death or ramorum leaf blight and dieback

Mycologist ◽  
2004 ◽  
Vol 18 (4) ◽  
pp. 151-156 ◽  
Author(s):  
BÉATRICE HENRICOT ◽  
CHRIS PRIOR
Keyword(s):  
Leaf Blight ◽  
Phytophthora Ramorum ◽  
Sudden Oak Death
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