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.

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.

scholarly journals Variation in Susceptibility of Tanoak to the NA1 and EU1 Lineages of Phytophthora ramorum, the Cause of Sudden Oak Death

Plant Disease ◽  
2019 ◽  
Vol 103 (12) ◽  
pp. 3154-3160 ◽  
Author(s):  
Kelsey L. Søndreli ◽  
Alan Kanaskie ◽  
Susanna Keriö ◽  
Jared M. LeBoldus
Keyword(s):  
Disease Resistance ◽  
Forest Ecosystems ◽  
Phytophthora Ramorum ◽  
Sudden Oak Death ◽  
Artificial Inoculation ◽  
Lesion Length ◽  
Significant Difference ◽  
Notholithocarpus Densiflorus ◽  
The Impact ◽  
Inoculation Assay

Phytophthora ramorum, the cause of sudden oak death (SOD), kills tanoak (Notholithocarpus densiflorus) trees in southwestern Oregon and California. Two lineages of P. ramorum are now found in wildland forests of Oregon (NA1 and EU1). In addition to the management of SOD in forest ecosystems, disease resistance could be used as a way to mitigate the impact of P. ramorum. The objectives of this study were to (i) characterize the variability in resistance of N. densiflorus among families using lesion length; (ii) determine whether lineage, isolate, family, or their interactions significantly affect variation in lesion length; and (iii) determine whether there are differences among isolates and among families in terms of lesion length. The parameters isolate nested within lineage (isolate[lineage]) and family × isolate(lineage) interaction explained the majority of the variation in lesion length. There was no significant difference between the NA1 and EU1 lineages in terms of mean lesion length; however, there were differences among the six isolates. Lesions on seedlings collected from surviving trees at infested sites were smaller, on average, than lesions of seedlings collected from trees at noninfested sites (P = 0.0064). The results indicate that there is potential to establish a breeding program for tanoak resistance to SOD and that several isolates of P. ramorum should be used in an artificial inoculation assay.

Proceedings of the coast redwood forests in a changing California: A symposium for scientists and managers

2012 ◽  
Author(s):  
Richard B. Standiford ◽  
Theodore J. Weller ◽  
Douglas D. Piirto ◽  
John D Stuart
Keyword(s):  
Coast Redwood ◽  
Redwood Forests

scholarly journals First Report of Foliar Infection of Maianthemum racemosum by Phytophthora ramorum

Plant Disease ◽  
2005 ◽  
Vol 89 (2) ◽  
pp. 204-204 ◽  
Author(s):  
D. Hüberli ◽  
K. L. Ivors ◽  
A. Smith ◽  
J. G. Tse ◽  
M. Garbelotto
Keyword(s):  
Mixed Forest ◽  
Personal Communication ◽  
Culture Collection ◽  
Phytophthora Ramorum ◽  
Internal Transcribed Spacer Region ◽  
Coast Redwood ◽  
First Report ◽  
Plastic Bags ◽  
Artificial Inoculations ◽  
Water Plants

In May 2003, Phytophthora ramorum S. Werres & A.W.A.M. de Cock was isolated from the leaf tips of a single plant of false Solomon's seal (Maianthemum racemosum (L.) Link, formely known as Smilacina racemosa (L.) Desf.), a native, herbaceous perennial of the Liliaceae family, at the Jack London State Park in Sonoma County, California. Affected leaves had cream-to-brown lesions on the tips that were delimited by a yellow chlorotic zone. Lesions on the stems were not observed. The isolate (American Type Culture Collection [ATCC], Manassas, VA, MYA-3280; Centraal Bureau voor Schimmelcultures, Baarn, the Netherlands, CBS 114391) was typical of P. ramorum with large chlamydospores and caduceus, semipapillate sporangia, and the sequence (GenBank Accession No. AY526570) of the internal transcribed spacer region of the rDNA matched those published previously (4). The site, from which wood rose (Rosa gymnocarpa) was recently identified as a host, is a mixed forest containing confirmed P. ramorum-infected coast redwood (Sequoia sempervirens), California bay laurel (Umbellularia californica), and tanoak (Lithocarpus densiflora) trees (2,3). Two leaves per asymptomatic, pesticide free, potted plant of false Solomon's seal were inoculated with zoospores of the P. ramorum isolate obtained from infected false Solomon's seal (1). Five plants were inoculated in trial 1, and the following day, three plants were inoculated in trial 2. A control leaf of each plant was dipped in sterile deionized water. Plants were enclosed in plastic bags, misted regularly with sterile distilled water, and maintained at 16 to 21°C in the greenhouse. In both trials, plants did not have lesions on the leaves after 16 days and were reinoculated on separate days for each trial with higher concentrations of zoospores (1 × 105 [trial 1] and 2 × 105 [trial 2] zoospores/ml). Cream-colored lesions, similar to those observed in the field, were evident 1 week after the second inoculation and stopped progressing in both trials by 17 days. Lesions starting from the leaf tips averaged 13 mm (range 8 to 24 mm) long, and P. ramorum was reisolated on Phytophthora-selective agar medium modified with 25 mg of pentachloronitrobenzene from 44% (trial 1) and 83% (trial 2) of all lesions (4). Control leaves had no lesions, and P. ramorum was not reisolated. Sporangia were not observed on any leaves when examined with the dissecting microscope. The fact that lesions developed only after a second inoculation with higher concentrations of zoospores, and these lesions stopped progressing after 17 days, suggests that false Solomon's seal is much less susceptible than other hosts such as western starflower (Trientalis latifolia) (1) and wood rose (2). To our knowledge, this is the first report of a plant from the Liliaceae as a natural host for P. ramorum, although Smilax aspersa was identified as being susceptible in artificial inoculations of detached leaves (E. Moralejo and L. Hernández, personal communication). False Solomon's seal is popular in the horticultural industry. References: (1) D. Hüberli et al. Plant Dis. 87:599, 2003. (2) D. Hüberli et al. Plant Dis. 88:430, 2004. (3) P. E. Maloney et al. Plant Dis. 86:1274, 2002. (4) D. M. Rizzo et al. Plant Dis. 86:205, 2002.

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.

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.

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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