What's New

New JKI Data Sheet - Plant Diseases and Diagnosis Phytophthora austrocedrae

Sabine Werres, Matthew Elliot, Alina Greslebin, 2014

Phytophthora austrocedrae Gresl. & E.M. Hansen is a Phytophthora species that up to now has only attacked needle trees and shrubs. It was first detected in Argentina on Austrocedrus chilensis (Chilean incense cedar, Cupressaceae). This conifer is naturally distributed in Argentina and in Chile. It is the most important conifer species of the Andean Patagonian forest. Disease symptoms had been observed since 1948 (Varsavsky et al., 1975 cited from Havrylenko et al.,1989; summary of the history of Austrocedrus chilensis decline in Filip & Rosso 1999, and La Manna & Matteucci 2012) but the causal agent could not be identified before 2007.

In Europe P. austrocedrae had first been reported in UK in spring 2011 in a public park where it could be isolated from diseased Chamaecyparis nootkatensis (Nootka cypress, Cupressaceae) and from C. lawsoniana. (Lawson’s cypress, Cupressaceae). The first cases of P. austrocedrae in the natural environment in the UK were discovered on Juniperus communis (common juniper, Cupressaceae) in the North Pennines, England in 2011. A recently made sequence analysis of an unknown Phytophthora isolate stored in the JKI culture collection showed that this isolate is a P. austrocedrae (Wagner and Werres, unpublishded data). It was isolated in 2001 from Juniperus horizontalis ‘Glauca’ (R. Ulrich, personal communication) and originated from a German nursery that imported plants. So it seems that P. austrocedrae has been present in Europe earlier than 2011.

Julius Kühn-Institut

Educational materials link...

 
Journal of Phytopathology Early View article 28 March 2014

Effects of Inoculum Density and Wounding on Stem Infection of Three Eastern US Forest Species by Phytophthora ramorum. Tooley, P. W., Browning, M. and Leighty, R. M. (2014), Journal of Phytopathology. doi: 10.1111/jph.12251

Abstract

Seedlings of three Eastern US forest species Quercus rubra (northern red oak), Quercus prinus (chestnut oak) and Acer rubrum (red maple) were inoculated by applying Phytophthora ramorum sporangia to stems at different inoculum densities with and without wounding. Disease occurred in all treatments involving wounds, and no disease was observed in unwounded treatments. Younger seedlings (2–3 years old) did not differ significantly from older seedlings (5–6 years old) in disease incidence, but older seedlings sustained smaller lesions compared with younger seedlings. For both old and young seedlings, disease on wounded stems was observed down to the lowest sporangia concentration utilized (500 sporangia/ml for old seedlings and 100 sporangia/ml for young seedlings). The results show that in the presence of wounding, even very low sporangia concentrations can result in disease, and further suggest that wounding caused by insects and other factors may play an important role in P. ramorum epidemiology in forest environments.

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When dieback kills the banksia, birds disappear

720 ABC Perth, 21 March, 2014.  By Sharon Kennedy

Studies by ECU show that banksia woodlands are critical for birds and plants in the south west.

Insect and nectar eating wrens are affected by dieback in banksia (Photo Davis: Rob Davis)

Dr Robert Davis says the researchers were astounded by the complete change in the bird community where dieback is prevalent.

Dieback, Phytophthora cinnamomi, is a soil borne pathogen which has been dubbed the biological bulldozer for its ability to wipe out plant species.

Jarrah and, particularly, banksia are susceptible. Currently, quarantine is the only effective method of control.

A lecturer in vertebrate biology, Dr Davis was drawn to the study of dieback in banksia in order to understand what was driving the disappearance of birds from the habitat.

"We have the world's only proteaceous woodlands that dominate our biota. It's a precious unique system that supports a whole host of nectar eating honey eaters."

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New Plant Pathology Accepted Article

Fungi and oomycetes in open irrigation systems: knowledge gaps and biosecurity implications

Zappia, RE, Huberli, D, Hardy, GESt.J, and Bayliss, KL, January 3, 2014http://doi.wiley.com/10.1111/ppa.12223

Water used for the irrigation of plants has the potential to harbour and spread plant pathogens yet little research is conducted within this field. This review was undertaken to critically review our understanding of water-borne fungal and oomycete plant pathogens in open irrigation systems, particularly in the context of plant biosecurity. It was determined that very limited data exists on these plant pathogens, with the majority of previous studies only recording pathogen presence. There are significant gaps in our knowledge of pathogen survival and spread, and very limited information on their ability to cause disease when contaminated irrigation water is applied to crops. This review has highlighted the need for new research on the epidemiology and pathogenicity of putative plant pathogens isolated from water, in order to determine their risk to crops. The importance of regular monitoring of irrigation systems for the early detection of plant pathogens is also discussed.

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Forest Pathology Early View article 12 March 2014

Strategies of attack and defence in woody plant–Phytophthora interactions. Forest Pathology. doi: 10.1111/efp.12096 Oßwald, W., et al.

This review comprises both well-known and recently described Phytophthora species and concentrates on Phytophthora–woody plant interactions. First, comprehensive data on infection strategies are presented which were the basis for three models that explain invasion and spread of Phytophthora pathogens in different woody host plants. The first model describes infection of roots, the second concentrates on invasion of the trunk, and the last one summarizes infection and invasion of host plants via leaves. On the basis of morphological, physiological, biochemical and molecular data, scenarios are suggested which explain the sequences of reactions that occur in susceptible and tolerant plants following infections of roots or of stem bark. Particular emphasis is paid to the significance of Phytophthora elicitins for such host–pathogen interactions. The overall goal is to shed light on the sequences of pathogenesis to better understand how Phytophthora pathogens harm their host plants.

Reference
New Plant Disease article March 2014

Foliar Blight and Shoot Dieback Caused by Phytophthora ramorum on Viburnum tinus in the Pistoia Area, Tuscany, Central Italy

B. Ginetti, S. Carmignani, A. Ragazzi, S. Werres, and S. Moricca Plant Disease 2014 98:3, 423-423
http://dx.doi.org/10.1094/PDIS-07-13-0767-PDN
In spring 2013, pot-grown Viburnum tinus plants shipped to an ornamental nursery in Pescia (Pistoia, central Italy, 287 m a.s.l., 43°54′0″ N, 10°41′0″ E) from another local nursery were found to bear disease symptoms. Symptoms included brown to black foliar lesions, later expanding into larger blotches; necrosis of the petioles; shoot wilting and folding; browning of the stems; and necrosis of the cambium. Infected leaves, shoots, and entire plants eventually died. Tissue samples (2 mm2) were cut at the edge of active lesions from tissue of the phloem, the xylem, and the leaves and plated on selective PARPNH V8 agar (V8A) (1). Rose-shaped and finely lobed cottony colonies arose in 2 to 3 days. Mono-hyphal colonies were isolated and transferred to V8A. Square colony pieces (1 cm2) from isolates SB05a and SB05b were placed in filtered pond water after 5 to 7 days. Semipapillate, caducous sporangia with a rounded or conical base were produced within 24 h, individually or in pairs, on each sporangiophore. Sporangia (n = 30 per isolate) were examined: they were 56.2 ± 9.5 × 29.3 ± 4.3 μm (l:b ratio 1.9 ± 0.3). Exit pores averaged 7.0 ± 1.0 μm. Sporangia were ellipsoid (30%), lemon-shaped (28.3%), ovoid (20%), obovoid (16.7%), ampulliform (3.3%), or “peanut-like” (1.7%). Globose chlamydospores, borne intercalarly or terminally, were abundant on both V8A and carrot agar (CA), and were on average 54.7 ± 8.5 μm. Mono-hyphal isolates incubated for 7 days at 23°C were also transferred to CA, corn meal agar (CMA), malt extract agar (MEA), potato dextrose agar (PDA), and V8A. Colonies on these media were identical in shape and appearance to those described in previous reports (2,4). Isolates were identified as Phytophthora ramorum Werres, De Cock & Man in't Veld (4) on the basis of colony type; size, the average l:b ratio and shape of sporangia; and the type and size of the chlamydospores. Isolates were found to be the A1 mating type by pairing them with P. cryptogea BBA 63651 (mating type A2). PCR-amplification of the rDNA ITS region with specific primers Ph1/Ph4 (3) gave fragments of the expected size (GenBank Accession Nos. KF181162 and KF181163). A BLAST search of these ITS sequences in the database found that isolates of P. ramorum were the closest phylogenetically with 100% homology (YQ653034 and HM004221). Pathogenicity tests were conducted on 16 detached V. tinus leaves. A small cut was made aseptically on each of the leaf surfaces and a V8A disc (0.5 cm Ø) with mycelium was placed over the wounds. Control leaves received only sterile V8A discs. Inoculated and control leaves were incubated at 23°C in the dark. Necrotic areas (average 3.5 ± 1.3 cm2) arose on inoculated leaves after 6 days. Control leaves had no symptoms. Re-isolations on PARPNH V8A confirmed P. ramorum as the causal agent. P. ramorum was reported in Italy in 2003 on the exotic Rhododendron yakushimanum (2). This is the first report of the pathogen on a native species (V. tinus) in this country. The Pistoia area is important for nursery gardens and flowers. P. ramorum, which probably arrived on infected plant material, could compromise the export/import trade in stock plants. For this reason, the plant protection services were promptly alerted and the infected plants were destroyed.
 
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New Plant Disease article March 2014

Phytophthora cinnamomi as a Contributor to White Oak Decline in Mid-Atlantic United States Forests

M. E. McConnell and Y. Balci Plant Disease 2014 98:3, 319-327

http://dx.doi.org/10.1094/PDIS-06-13-0649-RE

To evaluate Phytophthora cinnamomi as a cause of white oak (Quercus alba) decline in mid-Atlantic forests, sampling was conducted at 102 sites from 2011 to 2012. Soil and roots from healthy and declining white oak trees were collected. Phytophthora spp. were isolated using baiting and CFU of P. cinnamomi quantified using wet-sieving. Fine roots were scanned and measured. Phytophthora spp. were isolated from 43% of the sites. P. cinnamomi was common; six other species were isolated infrequently. Little difference in lesion size existed on white oak seedlings inoculated with 32 isolates of P. cinnamomi; only 13 isolates caused significant mortality. Soils from white oak versus nine other hosts did not have significantly different CFU. P. cinnamomi was restricted to United States Department of Agriculture hardiness zones six and seven and never found in zone five. The presence of Phytophthora spp. in soil can be associated with white oak fine root health. When Phytophthora spp. were present, white oak trees in zones five and six had less fine roots. In mid-Atlantic oak forests, however, environmental conditions appear to play a key role in determining the impact of P. cinnamomi on the root system. P. cinnamomi alone does not appear to be a causal factor of white oak decline.

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Excavator forest mulcher clearing Phytophthora Ramorum infected Larch

YouTube video

Published on Jan 17, 2014 by Justin Kingwell

Kobelco 200hp power-pack forest mulcher clearing Phytophthora Ramorum infected Larch before re-planting operations. Kingwell driver: Sean Barron.
Diseased larch felling to have 'huge impact' on Manx landscape

BBC News Isle of Man by Ellan Vannin 14 January 2014

Aerial surveys by the Forestry Commission in 2011 showed the affected areas (photo).

Aerial surveys by the Forestry Commission in 2011 showed the affected areas

Work to fell hundreds of thousands of infected larch trees in the Isle of Man will begin this week after an "explosion" of a deadly tree disease.

According to the Manx government about 50% of the island's larch population is currently infected by Phytophthora ramorum.

Forester Jason Bolt said the essential work will have a "huge impact on the island's landscape".

The Forestry Division plans to fell 450 hectares (1,111 acres) of larch.

Senior forester John Walmsley said the disease, first detected on the island in 2010, had "exploded" since March.

In July, a survey by the Manx Forestry Directorate showed a "considerable spread" of the disease in the north of the island.

Since then it has spread to the south, east and west.

'Vital step'

Mr Bolt said: "Larch makes up around 20% of our forests and in the short term it will have a major impact."

Environment Minister Phil Gawne said it was a "vital step" for which "quick action was needed".

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Cork’s Gougane Barra Forest Park closing due to tree fungus

The Irish Times Monday, January 13, 2014 by Barry Roche

Coillte to fell 16,000 trees in major operation to control spread of the disease

Coillte has confirmed it is to close Gougane Barra Forest Park in Co Cork for six months to allow for a major tree-felling operation after the discovery of a tree fungus attack.

According to Coillte forestry productivity manager Padraig Ó Tuama, an outbreak of the fungus phytophthora ramorum has been discovered in the popular forest park near Ballingeary.

Mr Ó Tuama said Coillte had taken the decision to fell about 16,000 trees – primarily Japanese larch – in Gougane Barra to prevent the spread of the disease. “Phytophthora ramorum is a fungus-like disease that can affect a range of trees and other plant species, with Japanese larch particularly susceptible,” he said.

“Coillte have been working closely with the Department of Agriculture, Food and the Marine to detect and prevent the spread of this disease. Regrettably, Gougane Barra is one of 20 Coillte forests where the disease has been confirmed in Japanese larch since first detected on the species in 2010.”

 

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