Natural stem infection of Lawson cypress (Chamaecyparis lawsoniana) caused by Phytophthora ramorum

This is the first report of C. lawsoniana as a natural host of P. ramorum. In November 2010, P. ramorum was isolated from a 4 m long by 60 cm wide aerial phloem lesion on another mature C. lawsoniana in a park near Clydebank, Scotland. There was heavy resinosis at the top of the lesion. Adjacent rhododendrons were also infected with P. ramorum. Ten other large C. lawsoniana at the Clydebank site had dieback and aerial or collar lesions caused by the recently introduced Phytophthora species, P. lateralis (SA Green, CM Brasier and JF Webber, unpublished). Such an overlap between P. ramorum and P. lateralis on C. lawsoniana on the same site is likely to lead to direct physical contact between the two species. Since they are closely related phylogenetically and produce similar fruiting structures (e.g. Brasier et al., 2010), such novel contact could result in their hybridisation (Brasier, 2000). This possibility is under investigation.

Read the full article here.

Killer disease found in two new species of Irish tree

Two thirds of Northern Ireland's forests are under threat from a killer tree disease.

The fungal disease P. ramorum (often called Sudden Oak Death) has already infected tens of thousands of Japanese larch trees.

This has led to the felling of over 200 hectares across nine woodlands.

The disease may have jumped species and has infected a Sitka spruce in the Republic of Ireland and several beech trees in County Down, in the north.

If the disease spreads to other Sitka trees it could be a disaster for the Northern Ireland Forestry Service. The species makes up two thirds of all government-owned forests in Northern Ireland.

The disease was already known to be able to infect beech trees. It has also been confirmed that the infection has been found in European larch in England.

BBC News

Read more here

UK House of Lords debate on SOD

Trees: Sudden Oak Death — Question
House of Lords debates, 10 February 2011, 11:21 am

Lord Greaves (Liberal Democrat)

To ask Her Majesty's Government what action they are taking to counter the spread of sudden oak death in trees.

Lord Henley (Parliamentary Under Secretary of State, Environment, Food and Rural Affairs; Conservative)

My Lords, the Forestry Commission and the Food and Environment Research Agency, working in partnership with other organisations, are delivering a five-year programme in England and Wales against Phytophthora ramorum. The Government take this very seriously. Infected Japanese larch is being cleared from 7,920 acres of woodland in an effort to halt the spread of the disease.

The rest of the debate

Characterizing Douglas-fir Tissue Colonization by the 'Sudden Oak Death' Pathogen, Phytophthora ramorum.

Characterizing Douglas-fir Tissue Colonization by the 'Sudden Oak Death' Pathogen, Phytophthora ramorum.
By Kathleen McKeever, M.S. and Dr. Gary Chastagner; Department of Plant Pathology, Washington State University Puyallup Research and Extension Center.

In 2001, Koch's Postulates confirmed Douglas-fir as a host for P. ramorum. Naturally-infected saplings have been observed in California forests, and studies on artificially inoculated Douglas-fir stems and shoots have established susceptibility parameters. Although naturally occurring stem infections in the U.S. have been limited to smaller diameter seedlings and saplings, P. ramorum stem cankers were recently observed on 8-year-old plantation grown Douglas-fir in Great Britain in 2009. All previous research has served to substantiate the importance of performing studies to characterize the behavior of P. ramorum in Douglas-fir and assess the potential risk that this pathogen poses to Douglas-fir ecosystems.

Artificial inoculation experiments were carried out to provide a thorough analysis of the colonization of Douglas-fir by P. ramorum. Goals of this research included determining which tissues are colonized by the pathogen, whether woody tissues are able to support sporulation, the likelihood of stem infections occurring on Douglas-fir with intact bark, and the viability of the pathogen in foliage. Methods employed included isolation, ELISA, and histological examination of stem tissues; qPCR and isolation to determine colonization efficacy and viability of the pathogen in needle tissues; and baiting studies to determine the ability of Douglas-fir bark to inhibit colonization of Rhododendron leaves by the pathogen.

ELISA results showed that proteins of the pathogen were detectable in the phloem, cambium, and superficial xylem, with infrequent detection in asymptomatic tissues. The pathogen was able to be isolated from all symptomatic woody tissues tested, but not from non-discolored tissues. ELISA and isolation techniques produced results that were highly positively correlated (r2=0.62, p=0.78), and histological observations paralleled information derived from these techniques. Douglas-fir bark reduced infection on Rhododendron leaf baits by up to 83 percent in the presence of inoculum. Results from foliage inoculations indicated that pathogen DNA is detectable using qPCR methods, but there was an inability to isolate the pathogen from needle tissue. Evidence of spore formation in woody stem tissues has not been observed.

It was concluded that the pathogen may be able to infect into the shallow xylem tissues of Douglas-fir in the presence of wounding, but there was no evidence of sporulation in tissues. The inability to isolate the pathogen from non-discolored tissues suggests that the proteins detected by ELISA outside of the lesion may be elicitins that are secreted in advance of hyphal colonization. The inability to isolate the pathogen from colonized needles may indicate the presence of chemical inhibitors that render the pathogen non-viable subsequent to initial infection. Finally, the ability of Douglas-fir bark to suppress infection of Rhododendron leaf baits suggests that the bark is inhibitory to P. ramorum and that infection of woody stem tissues through intact bark may be limited. Further research is required to identify the nature of this inhibition.

Characterization of P. ramorum colonization of Douglas-fir tissues is relevant to our current understanding of the behavior of the pathogen in different hosts and may enhance our ability to assess risk and create adequate regulations to thwart the spread of this exotic pathogen.

from the December COMTF newsletter

Deadly P lateralis tree disease found at Loch Lomond

A deadly tree disease never seen in Britain before has been detected on the shores of Loch Lomond.

P. lateralis is a close relative of P. ramorum and is a root pathogen on Port Orford Cedar.

Read the rest of the article here:

http://www.bbc.co.uk/news/uk-scotland-11879891

"Sudden Larch Death" in the UK

Plant pathology: Sudden larch death
Clive Brasier & Joan Webber
Nature 466:824–825
Date published:(12 August 2010)

doi:10.1038/466824a

An aggressive and unpredictable fungal pathogen is devastating larch plantations in Britain. Its remarkably broad host range, and the possibility of further geographical spread, give heightened cause for concern.

read the whole article here

SOD situation in Britain

Britain's Forestry Commission is continuing to try to minimize the spread of P. ramorum by felling tens of thousands of Japanese larch (Larix kaempferi), first found to be a sporulating host in southwest England in fall 2009. Since then, thousands of trees have died. Follow-up aerial surveys in southwest England and Wales, and up into western Scotland, have identified 203 suspicious sites in a mix of privately owned and Forestry Commission public woodlands in England and Wales. Of these, 42 sites in southwest England and eight in Wales have confirmed infestations. More than 30 hectares of trees were felled last winter, with an additional 250 hectares planned for removal this summer and fall. Felling is continuing in the southwest England counties of Devon and Cornwall, including Plym Woods, a popular forest for public recreation near the city of Plymouth, and is getting under way in Wales. The Forestry Commission hopes that by taking decisive action in southwest England and south Wales it can prevent the pathogen from spreading further into Britain.

Affected forests are remaining open to visitors, except for areas where felling is taking place, due to safety reasons. Visitors are being asked to stay on stone paths, keep dogs on short leads, and clean shoes and bikes before leaving infested areas. Private landowners are also being asked to regularly inspect woodlands where larch is present and to report any suspected P. ramorum outbreaks to the Forestry Commission. For more information, go to http://www.forestry.gov.uk/pramorum.

From the August COMTF newsletter

SOD found in South Wales on larch

Forestry Commission experts are working to contain the spread of Phytophthora ramorum infection to Japanese larch trees in South Wales.

Phytophthora ramorum (P. ramorum) is a fungus-like pathogen that kills many of the trees and plants that it infects. Japanese larch trees infected by P. ramorum were first found in South West England last year, the only place in the world where it has attacked large numbers of a commercially grown species of conifer tree.

This development was a step change in the pathogen’s behaviour. Since first being identified in Britain in 2002, on a viburnum plant in a garden centre, it had affected mostly shrub and ground-cover plants such as rhododendron, viburnum and bilberry. Fewer than 100 infected trees – mostly beech - had been found, and most of those were standing close to infected rhododendron bushes.

Although it has been confirmed in only one area of larch forest in Wales so far, Forestry Commission Wales expects to find more as ground inspections follow up the aerial surveys that have pinpointed suspect areas of woodland. Scientists at the Commission’s Forest Research arm believe it likely that the spores that spread the disease have been spread to the larch forests in rain, mists and air currents carried across the Bristol Channel from the South-west, where it was confirmed in Japanese larch last September.

Roddie Burgess, Head of the Forestry Commission’s Plant Health Service, said the Commission and its partners are taking the development very seriously, but hope to be able to contain it.

Read the complete article here:

http://www.forestry.gov.uk/newsrele.nsf/AllByUNID/11FB60906B36B2C68025773D005CD276