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Christmas Trees Threatened by Root Rot

Sci-Tech Today.com    By Allen G. Breed   December 3, 2013

Phytophthora root rot is a stubborn enemy for some Christmas tree growers this year. With no fungicide yet proven effective to control Phytophthora, many growers are turning to species from Europe, Asia that are more resistant. Researchers at Washington State and other universities are hoping to unlock the secrets to some species' rot resistance.

Jeff Pollard trudged up the steep slope and stopped at a desiccated, rust-brown tree. Two months earlier, workers had tagged this Fraser fir as ready for market.

It was going to be someone's Christmas tree. And now it was dead.

"Never get paid back for this tree," he said with a shrug. "Eleven years of work -- gone."

The culprit: Phytophthora root rot, a water mold that, once in the soil, makes it unfit for production.

Pollard has been growing Fraser fir in these western North Carolina mountains for nearly 40 years. To him, it's "the ultimate tree."

But this persistent problem has him looking to a species from the birthplace of old Saint Nicholas himself for a possible alternative. And he's not alone.

Isle of Man Today - Tree disease is hitting larch, sweet chestnut, beech and shrubs

Isle of Man Today- October 15, 2013

A disease that affects larch trees is continuing to ravage the island’s forestry, with about 50 hectares of trees felled and sweet chestnut, beech trees and garden shrubbery plants also affected.

The government has said that 50 per cent of the island’s larch population is now infected with the disease, phytophthora ramorum, also known as sudden oak death.

Area forester Jason Bolt said: ‘Sweet chestnut, beech and shrubbery plant species in gardens such as rhododendron have also been found to be infected in the island.’

Along with Dutch elm disease, phytophthora ramorum is one of two diseases affecting the island’s trees.

In addition, the Department of Environment, Food and Agriculture remains worried about the threat of a third, ash dieback.

Senior forester John Walmsley said: ‘To date we have felled thousands of trees clear felling an area of approximately 50 hectares throughout the forest estate due to phytophthora ramorum.

‘A further 20 to 30 hectares will be felled in the coming months and plans are being drawn up to deal with the most recent infected areas identified from our 2013 aerial surveys.

‘In an effort to contain the disease, the department has been and is continuing the clearfelling of infected areas as they are identified and as soon as is practical.

‘The public are requested to follow basic precautions during the problem, such as keeping to footpaths if requested to do so, keeping dogs on leads when walking in woodland areas and cleaning footwear and their animals before visiting other sites.’

New Plant Disease article

First report of Phytophthora plurivora causing collar rot on common alder in Spain

Mr. Mohammed Masum Ul Haque, Mr. Pablo Martínez-Álvarez, Mr. José María Lomba, Dr. Jorge Martín-García, and Prof. Julio Javier Diez

Phytophthora decline of riparian alder (Alnus spp.) has been reported in several European countries. Death of common alder (Alnus glutinosa) due to Phytophthora alni has also been reported in Spain. During several surveys of alder trees in September 2012, typical die-back symptoms, including sparse small yellowish foliage and the presence of rusty exudates on the bark at the collar and lower stem were observed in A.glutinosa growing on the banks of the river Tera (Langa de Duero, Soria, 41°36′34″N, 3°25′10″W, elevation 851 m) and the river Tormes (La Maya, Salamanca, 40°41′42″N, 5°35′36″W, elevation 833 m). Bark samples plus cambium were taken from the active lesions at collar region, cut into small pieces, dried on filter paper and plated on V8-PARPH agar. The samples were incubated for four days at 20 °C in the dark before obtaining the Phytophthora isolates.


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.


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.



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.


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.


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


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.


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.