Phytophthora species in streams

Hwang, J.; Jeffers, S.N.; and Oak, S.W. 2010. Aquatic habitats—A reservoir for population diversity in the genus Phytophthora. Phytopathology 100:S150.

Occurrences of oak decline and sudden oak death in forests of Europe and the west coast of the U.S.A., respectively, have focused attention on the species of Phytophthora present in natural ecosystems. We have been investigating the diversity of species of Phytophthora present in forest streams in the eastern U.S.A. Phytophthora spp. are well adapted to aquatic environments and can be recovered from stream water by baiting and filtration. Extensive surveys in multiple states revealed that a diversity of species occurs naturally in forest streams. In one study, five forest streams in western North Carolina were monitored monthly for a year. Seven species—P. cambivora, P. cinnamomi, P. citricola, P. citrophthora, P. gonapodyides, P. heveae, and P. pseudosyringae—and seven morphologically and genetically distinct groups of isolates were detected. Samples of stream-side soils and plants with symptoms also were collected, but only three species were detected: P. cinnamomi and P. heveae in soils and P. citricola and P. heveae on plants. Species of Phytophthora consistently were detected in streams during winter months when air temperatures were near or below freezing, which are not conducive to lesion development and sporulation. These results suggest that the native population of Phytophthora spp. in stream water is different from those in terrestrial habitats. The species of Phytophthora present in streams may occupy a unique niche—i.e., they appear to be aquatic inhabitants and not transient visitors.

Genetic diversity of P. ramorum population in Canada

Goss, E.M.; Larsen, M.; Vercauteren, A.; Werres, S.; Heungens, K.; and Grunwald, N.J. 2010. Genotypic diversity of Phytophthora ramorum in Canada. Phytopathology 100:S42.

Characterization of the genetic structure and diversity of the sudden oak death pathogen, Phythophthora ramorum, in ornamental nurseries in the United States has shown that all three known clonal lineages of the pathogen are present. The most common clonal lineage in U.S. nurseries has been the NA1 clonal lineage, which has the wider distribution in the United States as a result of interstate shipments of infected nursery stock. British Columbia (BC), Canada is also known to have nursery infestations of P. ramorum, and shipments of infected plants between the United States and BC have occurred. We investigated the genotypic diversity of P. ramorum in BC nurseries and compared this population to U.S. and European nursery populations. All three of the P. ramorum clonal lineages were found among Canadian nursery isolates, but the most common was the NA2 lineage. The NA1 clonal lineage was found infrequently in comparison to the United States. The EU1 lineage was observed almost every year and shared multilocus genotypes with isolates from Europe and the United States. Appropriate markers for the characterization of the NA2 lineage are needed.

Stream in NC positive for P. ramorum

Water draining an infested nursery in Mecklenburg County (Charlotte), NC has been found to have Phytophthora ramorum as a result of the 2010 National P. ramorum Early Detection Survey of Forests. The rhododendron leaf baits were deployed by survey cooperators in the NC Forest Service and diagnosis made from several baiting periods via PCR by the survey's Eastern Regional Diagnostic Lab at the Pennsylvania Department of Agriculture. This brings the total number of positive waterways to 10 in six states outside areas where P. ramorum is found in California and Oregon forest areas (WA [2], AL [4], MS [1], GA [1], FL [1], and NC [1]). Cooperative streamside vegetation surveys are being planned for the fall by the USDA Forest Service, NC Forest Service, and NC Department of Agriculture and Consumer Services to determine if the pathogen has become established in terrestrial ecosystems.

from COMTF July newsletter

Agency delays plan targeting sudden oak death

Nurseries say APHIS order provides more paperwork, but not more protection

By MITCH LIES

Capital Press

Federal officials provided West Coast nurseries breathing room this week when they delayed a new requirement for shipping nursery stock that can host sudden oak death.

But the delay falls short of easing industry concerns.

USDA Animal and Plant Health Inspection Service officials earlier this month told West Coast agriculture officials they planned to delay by as much as three weeks implementation of the federal order. It was initially scheduled to start June 21.

The order requires nurseries in Oregon, Washington and California to notify receiving states in writing when they ship nursery stock that can host Phytophthora ramorum, the fungus associated with sudden oak death.

Read the full article here - http://www.capitalpress.com/orewash/ml-sod-federal-order-062510

Two nurseries positive for P. ramorum in May

Washington was found to have two P. ramorum-positive nurseries in May. (1) On 5/3 a Thurston County wholesale/production nursery was found to have P. ramorum-positive Mahonia nervosa and Viburnum tinus as a result of a nursery compliance inspection. This nursery ships interstate and was previously positive for P. ramorum in 2008. Trace-forward and -back investigations are underway. (2) A Snohomish County wholesale nursery was determined to have P. ramorum-positive Rhododendron sp. on 5/6 as a result of a nursery compliance inspection. This nursery ships interstate and was previously positive for P. ramorum in 2008. Trace-forward and -back investigations are underway.

A Tale of Three Nurseries

A heartwarming (or frightening) tale of three nurseries, reposted from the Oregon Invasive Species blog:

Once upon a time there were three nurseries. As long as people could remember, these nurseries had been growing and selling plants to satisfied customers. The nurseries were called: Clean and Green, Pretty Good Plants, and Cuttin Corners....

read the whole story here:
http://oregoninvasivespecies.blogspot.com/2010/06/tale-of-three-nurseries.html

SOD found in South Wales on larch

Forestry Commission experts are working to contain the spread of Phytophthora ramorum infection to Japanese larch trees in South Wales.

Phytophthora ramorum (P. ramorum) is a fungus-like pathogen that kills many of the trees and plants that it infects. Japanese larch trees infected by P. ramorum were first found in South West England last year, the only place in the world where it has attacked large numbers of a commercially grown species of conifer tree.

This development was a step change in the pathogen’s behaviour. Since first being identified in Britain in 2002, on a viburnum plant in a garden centre, it had affected mostly shrub and ground-cover plants such as rhododendron, viburnum and bilberry. Fewer than 100 infected trees – mostly beech - had been found, and most of those were standing close to infected rhododendron bushes.

Although it has been confirmed in only one area of larch forest in Wales so far, Forestry Commission Wales expects to find more as ground inspections follow up the aerial surveys that have pinpointed suspect areas of woodland. Scientists at the Commission’s Forest Research arm believe it likely that the spores that spread the disease have been spread to the larch forests in rain, mists and air currents carried across the Bristol Channel from the South-west, where it was confirmed in Japanese larch last September.

Roddie Burgess, Head of the Forestry Commission’s Plant Health Service, said the Commission and its partners are taking the development very seriously, but hope to be able to contain it.

Read the complete article here:

http://www.forestry.gov.uk/newsrele.nsf/AllByUNID/11FB60906B36B2C68025773D005CD276