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Phytophthora ramorum found on larch in east Scotland

31 January 2013

Forestry Commission Scotland is advising woodland managers across Scotland of a confirmed case of Ramorum disease at Glen Dye, south of Banchory.

The outbreak is of concern because the fungus-like pathogen Phytophthora ramorum (‘Ramorum’) which causes the disease has so far been confined to the west coast of Scotland where the wetter climatic conditions are more suited to it.

Hugh Clayden, Tree Health Policy Adviser, for Forestry Commission Scotland, said:

“This outbreak is in a part of the country that is considered to be less climatically suitable for Ramorum - and which is also far from the nearest infected larch crops.

“We are currently investigating how the disease arrived at this location but one possibility is through unintentional transfer on vehicles using the public road. It serves as a timely reminder for everyone to remain alert to the risks to larch from P. ramorum and also highlights why biosecurity has become such an important part of forestry practice.

“Although the western half of Scotland is the most climatically suitable area for P. ramorum, given the right site and micro-climate conditions, coupled with suitable host species, it can occur anywhere. Early detection and rapid action are key to reducing the impacts of this disease and we are therefore most grateful to have received such a prompt and responsible response from the owner and manager of this site in taking swift action to remove the diseased trees.”


New Annual Review of Phytopathology article

Phytophthora Beyond Agriculture

Everett M. Hansen, Paul W. Reeser, and Wendy Sutton

Vol. 50: 359-378 DOI: 10.1146/annurev-phyto-081211-172946

Little is known about indigenous Phytophthora species in natural ecosystems. Increasing evidence, however, suggests that a diverse, trophically complex Phytophthora community is important in many forests. The number of described species has steadily increased, with a dramatic spike in recent years as new species have been split from old and new species have been discovered through exploration of new habitats. Forest soil, streams, and the upper canopies of trees are now being explored for Phytophthora diversity, and a new appreciation for the ecological amplitude of the genus is emerging. Ten to twenty species are regularly identified in temperate forest surveys. Half or more of this Phytophthora diversity comes from species described since 2000. Taxa in internal transcribed spacer (ITS) Clade 6 are especially numerous in forest streams and may be saprophytic in this habitat. Three ecological assemblages of forest Phytophthora species are hypothesized: aquatic opportunists, foliar pathogens, and soilborne fine-root and canker pathogens. Aggressive invasive species are associated with all three groups.

New Forest Phytophoras Journal article Dec 2012

Riedel, M., Werres, S., Elliott, E., McKeever, K., Shamoun, S.F. 2012. Histopathological investigations of the infection process and propagule development of Phytophthora ramorum on rhododendron leaves. Forest Phytophthoras 2(1). doi: 10.5399/osu/fp.2.1.3036


In Europe, cultivated rhododendron is one of the most important hosts for Phytophthora ramorum. To better understand leaf infection and leaf capacity for sporulation, infection studies were carried out. Detached leaves of Rhododendron ‘Catawbiense Grandiflorum ́ and `Brigitte ́ were inoculated with zoospore suspensions of P. ramorum isolates of mating type A1 and A2. ‘Catawbiense Grandiflorum’ developed much more leaf necrosis than ‘Brigitte’ (average necrotic leaf area after 55 days 106.5 mm2 versus 0.12 mm2). The trichomes on the ‘Brigitte’ leaves seemed to prevent the germ tubes from detecting the stomata. P. ramorum germ tubes from encysted zoospores invaded the leaf tissue via the stomata. Appressoria-like structures were observed. On the infected leaves new hyphae grew out of the stomata. Sporangia and chlamydospores developed on the mycelium from germinated zoospore cysts growing on the leaf surface as well as on the hyphae growing out of the stomata after infection. They could be observed mainly on the necrotic leaf areas. Single healthy-looking oospores developed within 12 days on the ‘Brigitte’ leaves. Observation of the infection process on leaves of Rhododendron ‘Cunningham’s White’ with the scanning electron microscope confirmed the various stages of the infection process.

Full Text: HTML

New Forest Phytophoras Journal article Dec 2012

Hansen, E., Reeser, P., Sutton, W., and Sims, L. 2012. Host and habitat index for Phytophthora species in Oregon. Forest Phytophthoras 2(1). doi: 10.5399/osu/fp.2.1.3026


Phytophthora species are abundant in streams in healthy forests and widespread in forest soils causing cryptic diseases, in addition to their more traditional roles as aggressive pathogens. We compiled existing Oregon records from available sources of reliably identified Phytophthora species from forests and forest trees and summarized the results by host and habitat in an interactive online database. Details of documented isolates including locations, available cultures, Genbank acquisition numbers, and citations are in an accompanying supplemental spreadsheet. Thirty-two Phytophthora species have been identified associated with 25 host species from Oregon forests or forest trees. This total includes 19 species recovered from forest streams and 19 from forest soils, generally in the absence of noticeable disease on associated vegetation.

A total of 29 Phytophthora species were identified from the various environments in forests. Fourteen species came from trees or forest shrubs growing in cultivated and urban environments. Only three species were unique to the latter, however, including P. ilicis, from cultivated holly (Ilex), and P. sansomeana and P. taxon ceanothus from forest nurseries. Three species, P. gonapodyides, P. taxon oaksoil, and P. taxon salixsoil were recovered from streams in all surveyed counties. The most widespread species causing root disease or bole cankers of trees was P. lateralis on Port-Orford-cedar in landscape plantings throughout the state as well as on forest trees in its limited native range. P. cambivora and P. cinnamomi were widespread but uncommon on a number of forest trees.

Early view Forest Pathology article, 21 January 2013

Identification of Phytophthora species baited and isolated from forest soil and streams in northwestern Yunnan province, China

W.-x. Huai, G. Tian, E. M. Hansen, W.-x. Zhao, E. M. Goheen, N. J. Grünwald and C. Cheng

Forest Pathology DOI: 10.1111/efp.12015

Phytophthora species were surveyed by collecting soil samples and placing bait leaves in selected streams during June–October in the years 2005, 2006 and 2010 at three sites in oak forests in Diqing Tibetan Autonomous Prefecture of NW Yunnan province, China. Seventy-three isolates of Phytophthora spp. were recovered from 135 baited leaf samples and 81 soil samples. Eight Phytophthora species were identified by observation of morphological features and ITS1-5.8S-ITS2 rDNA sequence analysis. The eight taxa included two well-known species P. gonapodyides and P. cryptogea, two recently described species P. gregata and P. plurivora, two named but as yet undescribed taxa, P. taxon PgChlamydo and P. taxon Salixsoil, and two previously unrecognized species, Phytophthora sp.1 and P. sp.2. The most numerous species, P. taxon PgChlamydo, and the second most abundant species, P. taxon Salixsoil, were recovered at all three sites. Phytophthora cryptogea was detected only once at site Nixi. Phytophthora gregata and P. sp.2 were isolated from a stream only at site Bitahai, while the other three species were each found at two sites. Phylogenetic analysis revealed that the isolates belonged to three ITS clades, one species including six isolates in clade 2, six species including 66 isolates in clade 6 and one species in clade 8. There was a relatively rich species and genetic diversity of Phytophthora detected in the investigated regions where the forest biotic and abiotic factors affecting the growth and evolution of Phytophthora populations were diverse.


Aggressive tree disease could cost millions

The Copenhagen Post

Christian Wenande December 29, 2012 - 06:59
Getting an overview on the spread of the Phytophthora in Denmark is not adequate, plant pathologist contends
In Denmark alone the economic damage sustained by the Phytophthora disease, shown here affecting the bark of a beech tree, could exceed hundreds of millions of kroner (Photo: Skov og Landskab)

If you’re on a stroll in the woods in 2013 and see a small net bag in a waterway or lake then do not remove it. Most likely, it’s not trash.

The net bag is part of the University of Copenhagen’s effort to get an overview of the country’s new and very aggressive tree disease, Phytophthora, which has begun wrecking havoc to a number of parks in the country.

Naturstyrelsen, the state nature agency, has granted funds to the pilot project that will take samples from as many as 60 trees throughout Denmark and combine them with visual observations of the trees from which the samples stem.

According to the Environment Ministry, similar efforts are being carried out in other EU and Scandinavian countries.

Phytophthora, which takes its name from the Greek and literally means ‘the plant destroyer’, is of the plant-damaging water-mould genus and has caused tremendous damage to crops and trees worldwide. In Denmark alone the economic damage sustained by the disease could exceed hundreds of millions of kroner.


Biosensors and Bioelectronics new article
Development of a lab-on-a-chip device for diagnosis of plant pathogens
Sandra Julich, Marko Riedel, Mark Kielpinski, Matthias Urban, Robert Kretschmer, Stefan Wagner, Wolfgang Fritzsche, Thomas Henkel, Robert Möller, Sabine Werres
Biosensors and Bioelectronics, Volume 26, Issue 10, 15 June 2011, Pages 4070-4075


A lab-on-a-chip system for rapid nucleic acid-based analysis was developed that can be applied for diagnosis of selected Phytophthora species as a first example for use in plant pathology. All necessary polymerase chain reaction process (PCR) and hybridization steps can be performed consecutively within a single chip consisting of two components, an inflexible and a flexible one, with integrated microchannels and microchambers. Data from the microarray is collected from a simple electrical measurement that is based on elementary silver deposition by enzymatical catalyzation. Temperatures in the PCR and in the hybridization zone are managed by two independent Peltier elements. The chip will be integrated in a compact portable system with a pump and power supply for use on site. The specificity of the lab-on-a-chip system could be demonstrated for the tested five Phytophthora species. The two Pythium species gave signals below the threshold. The results of the electrical detection of the microarray correspond to the values obtained with the control method (optical grey scale analysis).



In press: Revista Iberoamericana de Micología

Developing a taxonomic identification system of Phytophthora species based on microsatellites

J. del Castillo-Múnera, M. Cárdenas, A. Pinzón, A. Castañeda, A.J. Bernal, S. Restrepo

Phytophthora spp. is the most important genus of the Oomycete plant pathogens. Nowadays, there are 117 described species in this genus, most of them being primary invaders of plant tissues. The different species are causal agents of diseases in a wide range of crops and plants in natural environments. In order to develop control strategies against Phytophthora spp., it is important to know the biology, ecology and evolutionary processes of these important pathogens.


Hoopa Forestry Fighting to Stop Spread of Sudden Oak Death

Two Rivers Tribune, By Kristan Korns


Hoopa Tribal Forestry and UC Berkeley researchers are working to prevent the spread of an infestation of tree-killing spores which is now less than five miles from the boundary of the Hoopa Valley Reservation.

The spores, known as Phytophthora ramorum or Sudden Oak Death, can infect dozens of plant species and they kill Tan Oak trees. The disease has had devastating effects on forests in California and Oregon.

Darin Jarnaghan, the Hoopa Forestry Department manager, said, “The alarming thing is it’s getting closer. It’s moving eastward towards us.”

The disease is new, and isn’t fully understood yet by researchers and biologists. It wasn’t named until 2000, and was first found in Southern Humboldt in 2002. It has had devastating effects on forests in California and Oregon.

Yana Valachovic, the Director of the Humboldt and Del Norte University of California Cooperative Extension based out of Eureka, said that everyone was taken by surprise when the disease first appeared.

“This is an introduced pathogen to California. It’s not native, and we don’t know where it comes from,” Valachovic said. “The disease was discovered in Southern Humboldt around the Garberville/Redway area, but at the time they didn’t know what to do or how it spread.”





APHIS Revises Federal Order Requiring Notification for Phytophthora ramorum high-risk hosts

SUBJECT: APHIS Revises Federal Order Requiring Notification for Phytophthora ramorum high-risk hosts


Effective immediately, the Animal and Plant Health Inspection Service (APHIS) is amending two Federal Orders, dated January 28, 2011 (DA-2011-04) and February 25, 2011 (DA-2011-10) requiring advance notification for certain shipments of P. ramorum high-risk host nursery stock.


The attached Federal Order, which supersedes all previous Federal Orders on P. ramorum notification, removes notification requirements for nurseries in counties within regulated areas that have never tested positive for P. ramorum or have tested negative for the past three years.