Washington nursery update

Washington has had 10 confirmed positive nurseries to date in 2012, the most in a single year since 2006. Counties with detections include King, Pierce, Thurston, Lewis, Clark, Clallam, and Skagit. Eight of the nurseries are repeat positives and six are certified interstate host shippers, three of which have shipped host and associated host plant material in the past six months. Positive plants have included Rhododendron, Viburnum, Camellia, Magnolia, two Pieris, and one Gaultheria. With most of the positive nurseries in Washington catering to the landscape trade, and the housing industry slow, at least four of the 10 sites have had some of the currently positive plants in the nursery yard for over a year. It is unknown how long they have been infected on site.

From the July 2012 COMTF newsletter

Stream monitoring update

A stream in western Washington and one in northern Georgia have been found P. ramorum positive for the first time as a result of the National Early Detection Survey of Forests, bringing the total number of positives to date for this year to 14. Both new stream positives are in urban areas with current or formerly positive nurseries in the vicinity. Stream baiting will continue in an effort to identify the inoculum sources. In addition, the eight eastern sites in MS, AL, GA, FL, and NC found positive in the past have been confirmed positive again in 2012.

from the July COMTF newsletter

Fourth genetic lineage of Phytophthora ramorum pathogen identified

The increasing intensity of the P. ramorum outbreaks in the UK led researchers to analyze samples from the new findings further, which resulted in the discovery of a fourth genetically distinct lineage of the pathogen.
Announcing this at the Fifth Sudden Oak Death Symposium in California recently, Clive Brasier, an emeritus professor with the Forestry Commission's Forest Research agency, said he believed, based on genetic analysis, that the previously unknown European Type 2 (EU2) lineage had been recently introduced into south-west Scotland and Northern Ireland.

Read the full article here

Natural stem infection of Lawson cypress (Chamaecyparis lawsoniana) caused by Phytophthora ramorum

This is the first report of C. lawsoniana as a natural host of P. ramorum. In November 2010, P. ramorum was isolated from a 4 m long by 60 cm wide aerial phloem lesion on another mature C. lawsoniana in a park near Clydebank, Scotland. There was heavy resinosis at the top of the lesion. Adjacent rhododendrons were also infected with P. ramorum. Ten other large C. lawsoniana at the Clydebank site had dieback and aerial or collar lesions caused by the recently introduced Phytophthora species, P. lateralis (SA Green, CM Brasier and JF Webber, unpublished). Such an overlap between P. ramorum and P. lateralis on C. lawsoniana on the same site is likely to lead to direct physical contact between the two species. Since they are closely related phylogenetically and produce similar fruiting structures (e.g. Brasier et al., 2010), such novel contact could result in their hybridisation (Brasier, 2000). This possibility is under investigation.

Read the full article here.

Webinar - Scheduling Lawn and Garden Watering on your Smartphone or Web Browser

Learn how to plan your watering to eliminate flooding and Phytophthora problems. Attend this free webinar:

“Scheduling Lawn and Garden Watering on your Smartphone or Web Browser”

When do I turn the water on?  How long do I leave it on?  These are simple questions with difficult answers.  This webinar will describe how to use a new irrigation scheduling tool that runs equally well on a Smartphone or any web browser to greatly simplify making these decisions in a way that will result in green lawns and healthy gardens, save you work, and most importantly save on your water bill!

Tuesday May 29^th at 7:00 PM go to breeze.wsu.edu/rain and log in as a guest. Dr. Troy Peters, WSU Extension Irrigation Specialist will guide viewers  through the process and answer questions.

History is Key Factor in Plant Disease Virulence

A study of P. ramorum isolated from different hosts shows changes in virulence:

"The virulence of plant-borne diseases depends on not just the particular strain of a pathogen, but on where the pathogen has been before landing in its host, according to new research results.
Scientists from the University of California System and the U.S. Department of Agriculture's Agricultural Research Service (USDA ARS) published the results today in the journal PLoS ONE.
The study demonstrates that the pattern of gene regulation--how a cell determines which genes it will encode into its structure and how it will encode them--rather than gene make-up alone affects how aggressively a microbe will behave in a plant host.
The pattern of gene regulation is formed by past environments, or by an original host plant from which the pathogen is transmitted."

Read more in the press release from the National Science Foundation

Forest Insects and Diseases Arrive in US Via Imported Plants

ScienceDaily (Apr. 9, 2012) — The trade in live plants from around the world has become a major industry in the United States, with new imports now valued at more than $500 billion annually. According to a study conducted by researchers at UC Santa Barbara's National Center for Ecological Analysis and Synthesis, however, what has proved to be a boon for the economy has also been shown to have devastating effects on the environment.

(read more)