What's New

Colourful allure of sudden oak death

 

New Scientist blog, September 9, 2011

Sudden oak death doesn't sound pretty but snap it with the right camera, from the right angle, and it can look alluring.

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New Disease Reports 2011

First report of Phytophthora cinnamomi associated with stem cankers of Quercus cerris in South Africa

E. Oh, B.D. Wingfield, M.J. Wingfield and J. Roux

New Disease Reports (2011) 24, 11. [http://dx.doi.org/10.5197/j.2044-0588.2011.024.011]

Quercus cerris (Turkey oak) is native to the orient and southeastern Europe (Balci & Halmschlager, 2003a). These trees are also commonly planted as non-native ornamentals in countries including South Africa. Recently, bleeding cankers on the stems, typical of Phytophthora infection, were found on Q. cerris trees growing on the Vergelegen Estate near Somerset West in the Western Cape Province of South Africa (Fig. 1). Phytophthora species have been recognised as being involved in the decline of Quercus spp., including Q. cerris, in eastern and north-central USA and Europe (Balci et al., 2007). Species isolated from soil associated with declining Q. cerris include P. citricola, P. cryptogea, P. quercina, and P. syringae (Balci & Halmschlager, 2003a,b), while P. ramorum and P. cinnamomi have been isolated directly from sapwood of trees showing bleeding cankers in Europe (Brown & Brasier, 2007).

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Plant Pathology Early View article 24 Aug, 2011

Infectivity and sporulation potential of Phytophthora kernoviae to select North American native plants
E. J. Fichtner, D. M. Rizzo, S. A. Kirk, J. F. Webber

Phytophthora kernoviae exhibits comparable epidemiology to Phytophthora ramorum in invaded UK woodlands. Because both pathogens have an overlapping geographic range in the UK and often concurrently invade the same site, it is speculated that P. kernoviae may also invade North American (NA) forests threatened by P. ramorum, the cause of Sudden Oak Death. This paper addresses the susceptibility of select NA plants to P. kernoviae, including measures of disease incidence and severity on wounded and unwounded foliage. The potential for pathogen transmission and survival was investigated by assessing sporangia and oospore production in infected tissues. Detached leaves of Rhododendron macrophyllum, Rhododendron occidentale and Umbellularia californica, and excised roots of U. californica and R. occidentale were inoculated with P. kernoviae and percent lesion area was determined after 6 days. Leaves were then surface sterilized and misted to stimulate sporulation and after 24 h sporangia production was assessed. The incidence of symptomless infections and sporulation were recorded. All NA native plants tested were susceptible to P. kernoviae and supported sporangia production; roots of U. californica and R. occidentale were both susceptible to P. kernoviae and supported sporangia production. Oospore production was also observed in U. californica roots. The results highlight the vulnerability of select NA native plants to infection by P. kernoviae, suggest that symptomless infections may thwart pathogen detection, and underscore the importance of implementing a proactive and adaptive biosecurity plan.


Critically endangered species translocated (P. cinnamomi)

22 August 2011  Thirteen critically endangered plant species in WA’s Midwest and South Coast have successfully gone through translocation over the past year, with survival rates now ranging from 50–90 per cent, according to the Department of Environment and Conservation (DEC).

Translocation is the reintroduction of plants, animals or habitats from one location to another.

DEC research scientist Rebecca Dillon says translocations have been one of the most successful management actions to prevent extinction of critically endangered plants.

 

More at - Science Network Western Australia


Kauri killer now in Kaiwaka

 Friday, August 19, 2011 article in The Northern Advocate, NZ
   AT RISK: Kauri dieback is threatening Northland kauri trees, including Waipoua Forest giant Tane Mahuta.

A disease killing Northland's iconic kauri trees is spreading, a new infection being detected on private land in Kaiwaka.

Soil samples taken from a Kaiwaka farm have confirmed that kauri dieback is present in the soil and killing trees there.

Northland Regional Council biosecurity staff recently inspected the farm and collected the samples after the owner reported that kauri on his property appeared unhealthy and some were dying.

Continued at:http://www.northernadvocate.co.nz/news/kauri-killer-now-in-kaiwaka2/1073584/

                                                                  


Forest Pathology Early View article 4 Aug, 2011

Phytophthora ramorum in England and Wales: which environmental variables predict county disease incidence? Chadfield, V, Pautasso M.  Forest Pathology. 2011. 

Phytophthora ramorum is the oomycete pathogen responsible for Sudden Oak Death on the West Coast of the USA and Sudden Larch Death in the British Isles. It also causes twig dieback and leaf blight on a series of ornamental hosts (e.g. Rhododendron, Viburnum, Pieris and Camellia) commonly grown in plant nurseries, traded by garden centres and cultivated in public and private gardens. The role of the plant trade in the dispersal of P. ramorum has been well documented, but there is a need for regional analyses of which environmental variables can predict disease expression in the trade and in the wild, so as to be able to better predict the further development of this worldwide plant health issue. In this study, we analyse data on the incidence of P. ramorum (2002–2009, thus before the reports in Japanese larch plantations) in counties in England and Wales as a function of environmental variables such as temperature and rainfall, controlling for confounding factors such as county area, human population and spatial autocorrelation. While P. ramorum county incidence in nurseries and retail centres was positively related to county area and human population density, county incidence in gardens and the wild did not show such correlations, declined significantly towards the East and was positively correlated with disease incidence in the trade. The latter finding, although not conclusively proving causation, suggests a role of the trade in the dispersal of this pathogen across English and Welsh landscapes. Combined together, P. ramorum county incidence in the trade and in the semi-natural environment increased with increasing precipitation and with declining latitude. This study shows the importance of environmental variables in shaping regional plant epidemics, but also yields results that are suggestive of a role of people in spreading plant diseases across entire countries.

Reference


Larch tree disease found in Cumbria

8 AUGUST 2011

 

Ramorum disease of larch trees has been found in Cumbria for the first time.

The disease, which kills larch trees very quickly and is a recent arrival in Britain, has been confirmed in two woods in the Eskdale Valley in western Cumbria.

Larch trees produce large quantities of the spores that spread the disease, which can infect many species of trees and plants. The only available disease control treatment is to fell the trees, preferably before the next spore release, which current knowledge indicates occurs in the autumn.

 More at - UK Forestry Commission

 


Forest Pathology Early View article 11 Jul 2011

Isolation of Phytophthora lateralis from Chamaecyparis foliage in Taiwan
J. F. Webber, A. M. Vettraino, T. T. Chang, S.E. Bellgard, C. M. Brasier, A. Vannini

Article first published online: 11 JUL 2011

DOI: 10.1111/j.1439-0329.2011.00729.x

Summary

Following the discovery in 2008 of Phytophthora lateralis in forest soil under old-growth yellow cedar (Chamaecyparis obtusa var. formosana) in north-east Taiwan, further sampling was undertaken in the same region. Soil, root and symptomatic foliage samples were collected from five separate sites where C. obtusa was the dominant species in cloud forests at ca. 1800–2500 m. Soil and fine root samples were baited with cedar needles; both direct isolation and cedar needle baiting were used on foliage samples. Phytophthora lateralis was obtained from soil at three of the sites, but only from three of the 27 soil samples overall. Only one of 25 root samples yielded the pathogen, and this was associated with infested soil. Three foliage samples with symptoms visible as dark brown to black frond tips also yielded P. lateralis; these came from two different sites. This is the first record of P. lateralis infecting the foliage of C. obtusa. Moreover, when some of the symptomatic Chamaecyparis foliage segments were incubated, sporangia of P. lateralis formed on the necrotic tissues, sometimes in the axils of needle segments. The study provides evidence that P. lateralis has both a soil/root infecting phase and an aerial or foliar infecting phase in Taiwan, which is consistent with its unusual combination of water-dispersed (non-papillate) and aerially dispersed (caducous) sporangia. It also demonstrates the importance of investigating the biology, aetiology and ecological behaviour of Phytophthoras in their native, endemic environments.

Reference


Ramorum tree disease found in new region

Forestry Commision of Great Britain news release
30 JUNE 2011

Ramorum disease of larch trees has been found in Derbyshire’s Peak District.

The Forestry Commission has confirmed the disease in Japanese larch trees in a small woodland between Bakewell and Matlock, 80 miles from the nearest previously known outbreak in larch.

The disease, caused by the Phytophthora ramorum pathogen, can kill larch trees within a year of symptoms first being detectable. Japanese larch needles also produce huge quantities of the spores that spread the disease, so the trees must be felled quickly to limit its spread.

Continued at:

Ramorum tree disease found in new region


Strategy launched to tackle pest and disease threats to Britain's trees

Forestry Commission News 10 JUNE 2011 
Among the key new tree pests and diseases to emerge in Britain in recent years are Phytophthora ramorum, Phytophthora kernoviae, Phytophthora lateralis, acute oak decline, bleeding canker of horse chestnut caused by the bacterium Pseudomonas syringae ...

Strategy launched to tackle pest and disease threats to Britain's trees


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