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New Plant Disease article

First Report of Phytophthora Taxon Walnut in Lombardy, North Italy

Dr. Beatrice Ginetti, Prof. Alessandro Ragazzi, and Prof. Salvatore Moricca

The park Boscoincittà, Milan, North Italy (136 m a.s.l., 45º 29' 06" N, 9º 5' 32" E) has an area of 110 hectares and includes tree stands, wood clearings, trails and watercourses. Recently, common walnut (Jugland regia) trees in the park have begun to suffer from a progressive dieback that has caused roughly 90% mortality. Aerial symptoms were: stunted growth, loss of vigor, crown thinning and bark cankers with tarry exudates on the lower stem. The xylem tissue of trees showed large necrosis and flame-shaped discolouration below the bark. Since the dieback seemed caused by Phytophthora, samples were taken from 3 symptomatic trees and, by baiting, from the nearby soil and watercourses. Isolations from apple baits were carried out after a week. Isolations taken from tissue at the edge of active lesions of the trees were transferred on the selective medium V8A-PARPNH (1) and incubated at 24ºC. Cottony colonies appeared after 3 days and single hyphal tip derivatives were transferred to V8A for a further 4-7 days.

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Now available! Proceedings of the Sudden Oak Death Fifth Science Symposium

Citation:  Frankel, S.J.; Kliejunas, J.T.; Palmieri, K.M.; Alexander, J.M. tech. coords. 2013. Proceedings of the Sudden Oak Death Fifth Science Symposium. Gen. Tech. Rep. PSW-GTR-243. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. 169 p.

The Proceedings of the Sudden Oak Death Fifth Science Symposium provides an update on research to address sudden oak death, caused by the exotic, quarantine pathogen, Phytophthora ramorum. Over 60 submissions present national and inter- national investigations covering pathogen biology, biosecurity, genetics, monitoring, fire ecology, and diagnostics. Several papers on disease status and progress toward nursery and wildland management are also included.

 

http://www.fs.fed.us/psw/publications/documents/psw_gtr243/

Link here to access SOD Science Syposium proceedings on Forest Phytophthoras of the world.

 
Phytophthora-ID (version 2.0) revision

The current implementation of Phytophthora-ID (version 2.0) is completely revised to be faster and more stable.

Phytophthora-ID is a resource for the identification of Phytophthora species and genotypes using BLAST and R. The following resources are currently supported:

 

  • Species identification using the ITS region
  • Species identification using the cox spacer region
  • Placement of either P. ramorum or P. infestans into clonal lineages based on multilocus microsatellite data

 

The site includes carefully curated reference databases for the ITS, the cox spacer region and microsatellite data for P. ramorum and P. infestans.

 
Leave the Forest in the Forest

Snowdonia-Active News Item 26/07/2013

Natural Resources Wales has committed more than £2 million to help fight against a disease that is killing Britain's larch trees. Some 1,200 hectares (almost 3,000 acres) of larch trees have already been felled in Wales since the fungus-like organism, Phytophthora ramorum (P. ramorum), was first discovered here in June 2010.

As part of that fight Natural Resources Wales have launched a campaign 'Leave the Forest in the Forest', that calls on forest visitors to brush off twigs, leaves and any other forest debris from their clothes and cars when they visit any of their managed woodlands.

The video at the foot of the page urges mountain bikers to help stop the spread of tree diseases such as P. ramorum and ash dieback, by cleaning off any debris before they leave, by using a bike wash for example.

Dave Liddy of Natural Resources Wales, said: “Cleaning your bike is good for the bike, but it’s also good for the forest, too."

He added: “Our mountain bike trails are immensely popular and we want to encourage people to keep coming to our woodlands. Our message is a simple one. Enjoy yourselves, but please leave the forest in the forest.”

A further video is aimed at raising awareness of the issue among people who walk in the woods, horse riders or dog walkers.

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Early view Forest Pathology article, 12 July 2013

Scanu, B., Hunter, G. C., Linaldeddu, B. T., Franceschini, A., Maddau, L., Jung, T., Denman, S. (2013), A taxonomic re-evaluation reveals that Phytophthora cinnamomi and P. cinnamomi var. parvispora are separate species. Forest Pathology. doi: 10.1111/efp.12064

Between 2008 and 2011, severe dieback associated with root and collar rot was reported on Arbutus unedo in several sites in Sardinia, Italy. Isolations from infected tissues and rhizosphere soil samples consistently yielded a Phytophthora species. It was initially identified as Phytophthora cinnamomi var. parvispora Kröber and Marwitz by comparing morphological features with the original description and the internal transcribed spacer (ITS) sequences with those present in GenBank. A multigene phylogeny based on DNA sequence data from two nuclear (ITS and β-tubulin) and two mitochondrial (cox1 and cox2) gene regions combined with extensive morphological and physiological properties of these isolates, including the ex-type culture of P. cinnamomi var. parvispora, demonstrates that this taxon is unique and it is redesignated here as Phytophthora parvispora sp. nov. Although morphologically similar to P. cinnamomi, P. parvispora differs by its smaller-sized sporangia, chlamydospores, oogonia and oospores, higher oospore wall index, single-celled antheridia, higher minimum and maximum temperatures for growth and faster growth at optimum temperature. In the phylogeny, P. parvispora falls within Phytophthora ITS clade 7a, grouped in a well-supported clade sister to P. cinnamomi. In pathogenicity tests, P. parvispora and P. cinnamomi were equally aggressive towards A. unedo seedlings. The possible geographic origin of P. parvispora is also discussed.

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Early view Journal of Phytopathology article 8 July 2013

Chandelier, A., Heungens, K. and Werres, S. (2013), Change of Mating Type in an EU1 Lineage Isolate of Phytophthora ramorum. Journal of Phytopathology. doi: 10.1111/jph.12150

Abstract

All Phytophthora ramorum EU1 lineage isolates tested are of A1 mating type, except for three rare isolates from 2002 to 2003 from Belgium, which were originally assigned the A2 mating type. In one of these isolates (2338), a switch from A2 to A1 mating type was observed in 2006. This observation initiated a larger study in which all cultures and subcultures of the original three EU1 A2 isolates, maintained in three laboratories under different storage conditions, were checked for mating type change. The A2 to A1 mating type switch was observed in four of seven independently maintained isolates that were derived from isolate 2338 in two laboratories, using different transfer regimes and storage conditions. Following the mating type switch to A1 in these four derived isolates, no reversion back to A2 mating was observed, even after up to 5 years of additional isolate maintenance and several more subculturing events. The three other isolates that were derived from isolate 2338 as well as the other EU1 A2 isolates collected in 2002 and 2003 and stored in the same conditions did not display such mating type change. The potential causes of the mating type conversions as well as their epidemiological implications are discussed.

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Forest must be cleared after Sudden Oak Death disease discovered

Newsletter (Northern Ireland) 13 June 2013

More than 100 hectares of forest in Northern Ireland are to be cleared to help stop the spread of a deadly tree disease.

An outbreak of the infection caused by Phytophthora ramorum - or Sudden Oak Death as it is also known - has been confirmed in larch trees at Castlewellan Forest Park, Co Down, the Forest Service said.

Chief executive Malcolm Beatty said: “We are very disappointed about this outbreak in Castlewellan as it is further evidence that the disease is continuing to spread.

“We will clear over 100 hectares of forest to reduce the risk of the disease spreading to other forest species, and to recover as much of the timber as is possible.”

The disease was identified when many trees that were apparently healthy last autumn showed symptoms during the spring. Many have already died. Action to fell the trees is under way because this is the most effective way of preventing further spread.

Trees develop lesions and their shoots and foliage become wilted.

Visitors to the park have been urged to make sure their feet are clear of soil before visiting other areas to prevent spread of the infection.

 
Natural Resources Wales steps up fight against larch disease

News Wales 25 Jun 2013

Natural Resources Wales has committed more than £2 million into the fight to deal with a disease which is attacking Britain’s larch trees.

The new body, which looks after the Welsh environment, is to invest £500,000 straight away to combat Phytophthora ramorum (P ramorum) by cutting down trees around the edges of infected areas to try to stop it from spreading further.The urgent strategy also includes a groundbreaking trial to see if injecting trees with a common herbicide could be effective in slowing the spread of the disease.

Natural Resources Wales will spend a further £1.7 million to remove infected trees, replant those areas and to build forest roads so that new areas can be cleared.

Trefor Owen from Natural Resources Wales said:“This response shows how concerned we are about this disease because of its impact on timber markets, the landscape, woodland and other habitats.

“We understand the anxiety this is causing the private forestry sector and communities in the affected areas. We are liaising with the Welsh Government and affected forest owners to see how the economic and other impacts can be minimised.”The disease, which spreads through airborne spores from tree to tree, is proving difficult to contain and has moved more quickly than experts expected despite a massive effort to stop it in its tracks.

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Juniper tree disease threatens G&T

The Telegraph Thursday 20 June 2013

Phytophthora austrocedrae has been spotted on juniper bushes in the Lake District and Scotland.

 

The fungus could wipe out the delicate population of native juniper bushes in Britain Photo: ALAMY

 

The fungus could wipe out the delicate population of native juniper bushes in Britain.

The bluey green bushes used to be found around the country but are now confined to a few chalkland sites around the UK.

Many southern English counties have lost 60-70 per cent of their populations of juniper due to loss of habitat.

Now they are even more at risk if the disease spreads.

Some 45 per cent of Scottish trees are at risk of being wiped out by the fungus.

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New Disease Reports article 18 Jun 2013

Grijalba PE, Palmucci HE, Guillin E, Herrera C, 2013. Phytophthora multivora causing leaf spot on rhododendrons in Argentina. New Disease Reports 27, 20. DOI: 10.5197/j.2044-0588.2013.027.020

Rhododendron is a genus belonging to the family Ericaceae and contains over 1000 species commonly known as rhododendrons and azaleas (Dimitri, 1978). Phytophthora multivora is a species that was described in Western Australia in 2008 but before that it was misidentified as . citricola (Scott et al., 2009). During the early spring of 2011, leaf spot symptoms were observed on rhododendrons in two gardens in Tigre (northern Buenos Aires province) and in containers in a nursery near Buenos Aires city. Leaf spots were dark brown to almost black, visible on both sides near the leaf tips and margins, while tissue death continued down the leaf along the midrib (Fig. 1A). The veins under the diseased area of the leaves presented a reddish tint (Fig. 1B). Some leaves became brown and died, while in others the infection remained as spots on leaves.

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