Invasive Pathogens in Plant Biosecurity. Case Study: Phytophthora ramorum Werres et al.: Cause of Sudden Oak Death, Ramorum Leaf Blight and Ramorum Dieback

Diagnosis of Sudden Oak Death, ramorum leaf blight, and ramorum shoot dieback on a wide variety of hosts are discussed in detail, including the symptoms and signs, host range, taxonomy, and geographic distribution, as well as methods of isolation, identification, and storage of Phytophthora ramorum, the pathogen which causes Sudden Oak Death. Accepted for publication 6 June 2003. Published 7 July 2003.

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Microclimate Impacts Survival and Prevalence of Phytophthora ramorum in Umbellularia californica, a Key Reservoir Host of Sudden Oak Death in Northern California Forests

PLoS ONE ◽

10.1371/journal.pone.0098195 ◽

2014 ◽

Vol 9 (8) ◽

pp. e98195 ◽

Cited By ~ 8

Author(s):

Matthew V. DiLeo ◽

Richard M. Bostock ◽

David M. Rizzo

Keyword(s):

Reservoir Host ◽

Phytophthora Ramorum ◽

Sudden Oak Death ◽

Northern California ◽

Umbellularia Californica

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Optimal strategies to protect a sub-population at risk due to an established epidemic

10.1101/2021.09.10.459742 ◽

2021 ◽

Author(s):

Elliott H. Bussell ◽

Nik J. Cunniffe

Keyword(s):

National Park ◽

Optimal Strategies ◽

The Elderly ◽

Phytophthora Ramorum ◽

Limited Budget ◽

Redwood National Park ◽

Buffer Region ◽

The Face ◽

Test Robustness

AbstractEpidemics can particularly threaten certain sub-populations. For example, for SARS-CoV-2, the elderly are often preferentially protected. For diseases of plants and animals, certain sub-populations can drive mitigation because they are intrinsically more valuable for ecological, economic, socio-cultural or political reasons. Here we use optimal control theory to identify strategies to optimally protect a “high value” sub-population when there is a limited budget and epidemiological uncertainty. We use protection of the Redwood National Park in California in the face of the large ongoing state-wide epidemic of sudden oak death (caused by Phytophthora ramorum) as a case study. We concentrate on whether control should be focused entirely within the National Park itself, or whether treatment of the growing epidemic in the surrounding “buffer region” can instead be more profitable. We find that, depending on rates of infection and the size of the ongoing epidemic, focusing control on the high value region is often optimal. However, priority should sometimes switch from the buffer region to the high value region only as the local outbreak grows. We characterise how the timing of any switch depends on epidemiological and logistic parameters, and test robustness to systematic misspecification of these factors due to imperfect prior knowledge.

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Invasive Insects in Plant Biosecurity: Case Study – Mediterranean Fruit Fly

The Handbook of Plant Biosecurity ◽

10.1007/978-94-007-7365-3_15 ◽

2013 ◽

pp. 447-484 ◽

Cited By ~ 8

Author(s):

D. R. Lance ◽

W. M. Woods ◽

M. Stefan

Keyword(s):

Fruit Fly ◽

Mediterranean Fruit Fly ◽

Invasive Insects ◽

Plant Biosecurity

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

Canadian Journal of Forest Research ◽

10.1139/x11-020 ◽

2011 ◽

Vol 41 (4) ◽

pp. 763-772 ◽

Cited By ~ 18

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.

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

Plant Disease ◽

10.1094/pdis-92-11-1566 ◽

2008 ◽

Vol 92 (11) ◽

pp. 1566-1573 ◽

Cited By ~ 26

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.

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

Plant Disease ◽

10.1094/pdis-03-20-0619-re ◽

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.

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

Phytopathology ◽

10.1094/phyto-05-20-0164-r ◽

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.

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