Phytophthora ramorum is the oomycete pathogen responsible for Sudden Oak Death on the West Coast of the USA and Sudden Larch Death in the British Isles. It also causes twig dieback and leaf blight on a series of ornamental hosts (e.g. Rhododendron, Viburnum, Pieris and Camellia) commonly grown in plant nurseries, traded by garden centres and cultivated in public and private gardens. The role of the plant trade in the dispersal of P. ramorum has been well documented, but there is a need for regional analyses of which environmental variables can predict disease expression in the trade and in the wild, so as to be able to better predict the further development of this worldwide plant health issue. In this study, we analyse data on the incidence of P. ramorum (2002–2009, thus before the reports in Japanese larch plantations) in counties in England and Wales as a function of environmental variables such as temperature and rainfall, controlling for confounding factors such as county area, human population and spatial autocorrelation. While P. ramorum county incidence in nurseries and retail centres was positively related to county area and human population density, county incidence in gardens and the wild did not show such correlations, declined significantly towards the East and was positively correlated with disease incidence in the trade. The latter finding, although not conclusively proving causation, suggests a role of the trade in the dispersal of this pathogen across English and Welsh landscapes. Combined together, P. ramorum county incidence in the trade and in the semi-natural environment increased with increasing precipitation and with declining latitude. This study shows the importance of environmental variables in shaping regional plant epidemics, but also yields results that are suggestive of a role of people in spreading plant diseases across entire countries.
8 AUGUST 2011
Ramorum disease of larch trees has been found in Cumbria for the first time.
The disease, which kills larch trees very quickly and is a recent arrival in Britain, has been confirmed in two woods in the Eskdale Valley in western Cumbria.
Larch trees produce large quantities of the spores that spread the disease, which can infect many species of trees and plants. The only available disease control treatment is to fell the trees, preferably before the next spore release, which current knowledge indicates occurs in the autumn.
More at - UK Forestry Commission
Isolation of Phytophthora lateralis from Chamaecyparis foliage in Taiwan
J. F. Webber, A. M. Vettraino, T. T. Chang, S.E. Bellgard, C. M. Brasier, A. Vannini
Article first published online: 11 JUL 2011
Following the discovery in 2008 of Phytophthora lateralis in forest soil under old-growth yellow cedar (Chamaecyparis obtusa var. formosana) in north-east Taiwan, further sampling was undertaken in the same region. Soil, root and symptomatic foliage samples were collected from five separate sites where C. obtusa was the dominant species in cloud forests at ca. 1800–2500 m. Soil and fine root samples were baited with cedar needles; both direct isolation and cedar needle baiting were used on foliage samples. Phytophthora lateralis was obtained from soil at three of the sites, but only from three of the 27 soil samples overall. Only one of 25 root samples yielded the pathogen, and this was associated with infested soil. Three foliage samples with symptoms visible as dark brown to black frond tips also yielded P. lateralis; these came from two different sites. This is the first record of P. lateralis infecting the foliage of C. obtusa. Moreover, when some of the symptomatic Chamaecyparis foliage segments were incubated, sporangia of P. lateralis formed on the necrotic tissues, sometimes in the axils of needle segments. The study provides evidence that P. lateralis has both a soil/root infecting phase and an aerial or foliar infecting phase in Taiwan, which is consistent with its unusual combination of water-dispersed (non-papillate) and aerially dispersed (caducous) sporangia. It also demonstrates the importance of investigating the biology, aetiology and ecological behaviour of Phytophthoras in their native, endemic environments.
Forestry Commision of Great Britain news release
30 JUNE 2011
Ramorum disease of larch trees has been found in Derbyshire’s Peak District.
The Forestry Commission has confirmed the disease in Japanese larch trees in a small woodland between Bakewell and Matlock, 80 miles from the nearest previously known outbreak in larch.
The disease, caused by the Phytophthora ramorum pathogen, can kill larch trees within a year of symptoms first being detectable. Japanese larch needles also produce huge quantities of the spores that spread the disease, so the trees must be felled quickly to limit its spread.
Forestry Commission News 10 JUNE 2011
Among the key new tree pests and diseases to emerge in Britain in recent years are Phytophthora ramorum, Phytophthora kernoviae, Phytophthora lateralis, acute oak decline, bleeding canker of horse chestnut caused by the bacterium Pseudomonas syringae ...
Enhanced Recovery of Phytophthora ramorum from Soil Following 30 Days of Storage at 4°C
Paul W. Tooley, Marie M. Carras
Article first published online: 1 JUN 2011
Chlamydospores of Phytophthora ramorum were used to infest field soil at densities ranging from 0.2 to 42 chlamydospores/cm3 soil. Recovery was determined by baiting with rhododendron leaf discs and dilution plating at time 0 and after 30 days of storage at 4°C, as recommended by USDA-APHIS. Baiting was slightly more sensitive than dilution plating in recovering P. ramorum immediately following infestation of soil and allowed detection from samples infested with as little as 0.2 chlamydospores/cm3 compared with 1 chlamydospore/cm3 for dilution plating. After 30 days of infested soil storage at 4°C, P. ramorum was detected at significantly (P = 0.05) higher levels than at time 0 with both recovery methods. The results indicate that storage of P. ramorum-infested soil at 4°C may allow for pathogen activity, such as sporangia production, which may enhance recovery from soil.
Roaches Estate bilberry plants hit by fungal disease
Bilberry plants at a Staffordshire beauty spot have been infected by a rare fungal disease.
Phytophthora pseudosyringae has killed some plants near Roach End on the Roaches Estate, near Leek. The disease does not harm humans or animals.
People have been asked to help prevent the disease spreading by avoiding contact with the shrubs, although the area remains open to the public.
This is Cornwall
Tuesday, May 10, 2011
Some 1,745 hectares (4,300 acres) of Japanese larch has had to be felled in Cornwall, Devon and Somerset to combat the spread of Phytophthora ramorum, a fatal disease first found locally in 2007...