The effects of Phytophthora ramorum infection on hydraulic conductivity and tylosis formation in tanoak sapwood

2009 ◽  
Vol 39 (9) ◽  
pp. 1766-1776 ◽  
Author(s):  
Bradley R. Collins ◽  
Jennifer L. Parke ◽  
Barb Lachenbruch ◽  
Everett M. Hansen
Keyword(s):  
Hydraulic Conductivity ◽  
Water Transport ◽  
Specific Conductivity ◽  
Phytophthora Ramorum ◽  
Sudden Oak Death ◽  
Inoculation Site ◽  
Lithocarpus Densiflorus ◽  
Stem Water ◽  
Spread Of Infection ◽  
Flow Over Time

Tanoak ( Lithocarpus densiflorus (Hook. and Arn.) Rehder) is highly susceptible to sudden oak death, a disease caused by the oomycete Phytophthora ramorum Werres, De Cock & Man in’t Veld. Symptoms include a dying crown, bleeding cankers, and, eventually, death of infected trees. The cause of mortality is not well understood, but recent research indicates that water transport is reduced in infected trees. One possible mechanism causing the reduction in hydraulic conductivity is the presence of tyloses in xylem vessels. The development of tyloses was studied in relation to hydraulic conductivity in P. ramorum-infected sapwood. Inoculated logs showed a greater abundance of tyloses than noninoculated logs after 4 weeks. Inoculated trees with xylem infections had significantly more tyloses than noninoculated trees. In addition, the increase in number of tyloses was associated with a decrease in specific conductivity, suggesting that tyloses induced by infection with P. ramorum may interfere with stem sap flow. Over time, tylosis development increased in tissues farther from the inoculation site, in advance of the vertical spread of infection. The results suggest that infected sapwood contains numerous tyloses, which could significantly impede stem water transport.

scholarly journals Phytophthora ramorum Colonizes Tanoak Xylem and Is Associated with Reduced Stem Water Transport

2007 ◽  
Vol 97 (12) ◽  
pp. 1558-1567 ◽  
Author(s):  
J. L. Parke ◽  
E. Oh ◽  
S. Voelker ◽  
E. M. Hansen ◽  
G. Buckles ◽  
...  
Keyword(s):  
Specific Conductivity ◽  
Vessel Diameter ◽  
Phytophthora Ramorum ◽  
Heat Diffusion ◽  
Sap Flux ◽  
Tissue Samples ◽  
Lithocarpus Densiflorus ◽  
Polymerase Chain ◽  
Stem Water ◽  
Radial Spread

Isolation, detection with diagnostic polymerase chain reaction (PCR), and microscopy demonstrated the presence of Phytophthora ramorum in the sapwood of mature, naturally infected tanoak (Lithocarpus densiflorus) trees. The pathogen was strongly associated with discolored sapwood (P < 0.001), and was recovered or detected from 83% of discolored sapwood tissue samples. Hyphae were abundant in the xylem vessels, ray parenchyma, and fiber tracheids. Chlamydospores were observed in the vessels. Studies of log inoculation indicated that P. ramorum readily colonized sapwood from inoculum placed in the bark, cambium, or sapwood. After 8 weeks, radial spread of P. ramorum in sapwood averaged 3.0 to 3.3 cm and axial spread averaged 12.4 to 18.8 cm. A field study was conducted to determine if trees with infected xylem had reduced sap flux and reduced specific conductivity relative to noninfected control trees. Sap flux was monitored with heat-diffusion sensors and tissue samples near the sensors were subsequently tested for P. ramorum. Adjacent wood sections were excised and specific conductivity measured. Both midday sap flux and specific conductivity were significantly reduced in infected trees versus noninfected control trees. Vessel diameter distributions did not differ significantly among the two treatments, but tyloses were more abundant in infected than in noninfected trees. Implications for pathogenesis, symptomology, and epidemiology are discussed.

scholarly journals Sudden Oak Death Caused by Phytophthora ramorum in Oregon

Plant Disease ◽  
2002 ◽  
Vol 86 (4) ◽  
pp. 441-441 ◽  
Author(s):  
E. M. Goheen ◽  
E. M. Hansen ◽  
A. Kanaskie ◽  
M. G. McWilliams ◽  
N. Osterbauer ◽  
...  
Keyword(s):  
San Francisco ◽  
Aerial Survey ◽  
Selective Medium ◽  
Phytophthora Ramorum ◽  
Its Sequences ◽  
Sudden Oak Death ◽  
Usda Forest Service ◽  
Plant Materials ◽  
Solid Media ◽  
Lithocarpus Densiflorus

Sudden oak death, caused by Phytophthora ramorum (1,2), has been found for the first time in Oregon, killing tanoak, Lithocarpus densiflorus, trees. To our knowledge, this is the first report of the disease outside of the San Francisco to Monterey area in California, (300 km to the south). Nine areas of infestation, all within a 24-km2 area, were discovered on forest lands near Brookings, in southwest Oregon. Mortality centers ranged in size from 0.2 to 4.5 ha and included 5 to approximately 40 diseased trees. P. ramorum was isolated from stem cankers using Phytophthora-selective medium. Isolates had distinctive morphological features characteristic of P. ramorum, including abundant production of chlamydospores and caducous, semipapillate sporangia on solid media. Internal transcribed spacer (ITS) sequences of isolates of P. ramorum from Oregon were identical to ITS sequences of isolates from California (1). The pathogen also was isolated from necrotic lesions on leaves and stems of native Rhododendron macrophyllum and Vaccinium ovatum growing beneath diseased tanoaks. In July 2001, the disease was located by an aerial survey conducted cooperatively by the USDA Forest Service and Oregon Department of Forestry. All lands within 1.6 km (1 mile) of the mortality centers are subject to Oregon quarantine, which bars the transport of any host plant materials. An eradication effort is currently underway. Symptomatic plants and all known host plants within 15 to 30 m of symptomatic plants are being cut and burned in the first phase of this operation. The total treated area is approximately 16 ha. References: (1) D. M. Rizzo et al. Plant Dis. In press. (2) S. Werres et al. Mycol. Res. 105:1155, 2001.

scholarly journals Stream Monitoring for Detection of Phytophthora ramorum in Oregon Tanoak Forests

Plant Disease ◽  
2009 ◽  
Vol 93 (11) ◽  
pp. 1182-1186 ◽  
Author(s):  
W. Sutton ◽  
E. M. Hansen ◽  
P. W. Reeser ◽  
A. Kanaskie
Keyword(s):  
Host Plants ◽  
Selective Medium ◽  
Phytophthora Ramorum ◽  
Sudden Oak Death ◽  
Chain Reaction ◽  
Stream Monitoring ◽  
Lithocarpus Densiflorus ◽  
Bait Station ◽  
Mesh Bags ◽  
Polymerase Chain

Stream monitoring using leaf baits for early detection of Phytophthora ramorum has been an important part of the Oregon Sudden Oak Death (SOD) program since 2002. Sixty-four streams in and near the Oregon quarantine area in the southwest corner of the state were monitored in 2008. Leaves of rhododendron (Rhododendron macrophyllum) and tanoak (Lithocarpus densiflorus) were placed in mesh bags, and bags were floated in streams. Leaf baits were exchanged every 2 weeks throughout the year. Leaves were assayed by isolation on selective medium and by multiplex rDNA internal transcribed spacer polymerase chain reaction (ITS PCR). The two methods gave comparable results, but multiplex PCR was more sensitive. P. ramorum was regularly recovered at all seasons of the year from streams draining infested sites 5 years after eradication treatment. In streams with lower inoculum densities, recovery was much higher in summer than in winter. P. ramorum was isolated from streams in 23 watersheds. When P. ramorum was detected, intensive ground surveys located infected tanoaks or other host plants an average of 306 m upstream from the bait station. P. ramorum was isolated from stream baits up to 1,091 m from the probable inoculum source.

scholarly journals Phytophthora ramorum as the Cause of Extensive Mortality of Quercus spp. and Lithocarpus densiflorus in California

Plant Disease ◽  
2002 ◽  
Vol 86 (3) ◽  
pp. 205-214 ◽  
Author(s):  
D. M. Rizzo ◽  
M. Garbelotto ◽  
J. M. Davidson ◽  
G. W. Slaughter ◽  
S. T. Koike
Keyword(s):  
The Netherlands ◽  
Phytophthora Ramorum ◽  
Sudden Oak Death ◽  
Central Coast ◽  
Outer Bark ◽  
Canker Disease ◽  
Quercus Agrifolia ◽  
Lithocarpus Densiflorus ◽  
Quercus Spp ◽  
Diagnostic Symptoms

A new canker disease, commonly known as sudden oak death, of Lithocarpus densiflorus, Quercus agrifolia, Q. kelloggii, and Q. parvula var. shrevei in California is shown to be caused by Phytophthora ramorum. The pathogen is a recently described species that previously was known only from Germany and the Netherlands on Rhododendron spp. and a Viburnum sp. This disease has reached epidemic proportions in forests along approximately 300 km of the central coast of California. The most consistent and diagnostic symptoms on trees are cankers that develop before foliage symptoms become evident. Cankers have brown or black discolored outer bark and seep dark red sap. Cankers occur on the trunk at the root crown up to 20 m above the ground, but do not enlarge below the soil line into the roots. Individual cankers are delimited by thin black lines in the inner bark and can be over 2 m in length. In L. densiflorus saplings, P. ramorum was isolated from branches as small as 5 mm in diameter. L. densiflorus and Q. agrifolia were inoculated with P. ramorum in the field and greenhouse, and symptoms similar to those of naturally infected trees developed. The pathogen was reisolated from the inoculated plants, which confirmed pathogenicity.

Stem—Water Transport

1984 ◽  
pp. 17-17
Author(s):  
Janice Glimn-Lacy ◽  
Peter B. Kaufman
Keyword(s):  
Water Transport ◽  
Stem Water

Phytophthora ramorum. [Distribution map].

2006 ◽  
Author(s):  
Keyword(s):  
South Carolina ◽  
Phytophthora Ramorum ◽  
Distribution Map ◽  
Quercus Agrifolia ◽  
Quercus Kelloggii ◽  
Live Oak ◽  
Lithocarpus Densiflorus ◽  
Black Oak ◽  
New Distribution ◽  
Distribution In Europe

Abstract A new distribution map is provided for Phytophthora ramorum Werres, de Cock & Man in't Veld. Oomycota: Pythiales. Hosts include California black oak (Quercus kelloggii), California live oak (Quercus agrifolia), Rhododendron, shreve oak (Quercus parvula var. shrevei), tanoak (Lithocarpus densiflorus) and Viburnum. Information is given on the geographical distribution in Europe (Belgium, Denmark, France, Germany, Ireland, Italy, Netherlands, Norway, Poland, Slovenia, Spain, Sweden, Switzerland, UK) and North America (Canada (British Columbia), USA (California, Florida, Georgia, Louisiana, Oregon, South Carolina, Tennessee, Virginia, Washington)).

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.

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