On Friday, the San Francisco Chronicle published a story about Sudden Oak Death and the spread of P. ramorum in waterways. It mentioned that ten streams, ditches, or ponds in six states have now been found infested with P. ramorum. Many of these are states that are officially considered uninfested because the pathogen has not been found in the forest environment. In all these cases, the pathogen has been linked to nearby nurseries that have at one time or another carried infested ornamental plants.
The article points out that the most mysterious case is right here in Humboldt County. Two streams in McKinleyville, north of Arcata, are infested with P. ramorum. Although both streams run through heavily developed residential neighborhoods, we from UC Cooperative Extension have teamed up with Humboldt County Ag Department and Redwood National Park personnel to try to find the source of the spores in the stream by walking as much of the streambanks as possible to find symptomatic plants--and so far, we have found nothing in two seasons of looking.
Near both streams, there is very little host material for P. ramorum to infect. There are very few ornamental hosts and almost no bay or tanoak. The bright side may be that this paucity of host material means little chance of the pathogen's escaping the stream and spreading further. Another positive is that at the point where P. ramorum has been recovered in each stream, the waterways empty into the ocean in short order.
Although a nearby nursery in McKinleyville has had infected plants at various times in the past, there is no definite link between the nursery and the streams--the streams are too far away for water from the nursery to easily make its way to the streams--unlike in other states, where it's obvious how infested runoff exited each nursery and made its way to each nearby waterway.
The mysterious cases of persistent spores in these streams highlight the troubling difficulty of definitively ridding infested nurseries and forests of P. ramorum. 
Monitoring Rock Creek in Del Norte County for Phytophthora ramorum using rhododendron leaf baits.
When stars make an appearance in Hollywood the paparazzi are sure to follow, cameras in tow. In Santa Cruz it seems that is not the case, not unless you count the handycam my fellow blogger, Janice Alexander, set-up. Though we had the world’s best and brightest the only fanfare was a round of applause after the celebrities gave their presentations. Who were these cynosures you ask? World leaders in the field of Phytophthora.
In the coming weeks, I’ll be working to digitize, edit and post the talks from the Fourth Sudden Oak Death Science Symposium, but until that work is complete, I’d like to highlight a few of the informative and inspirational presentations.
The first-up on my Top 10 list is a talk given by Dr. Jennifer Parke, plant pathologist at Oregon State University.
Dr. Parke presented her lab’s work, done in collaboration with Dr. Nik Grünwald’s lab at USDA-ARS Corvallis, on a systems approach to detecting sources of Phytophthora contamination in nurseries. The system, modeled after the food industries Hazard Analysis Critical Control Points (HACCP) which ensures food products are not contaminated during processing, focuses on Critical Control Points (CCPs) that is points at which a serious hazard of Phytophthora contamination can be controlled.
Over the last 3 years, Parke and Grünwald have worked with four nurseries on identifying the CCPs in nursery production and developing best management practices to mitigate contamination. Though the study focuses on Phytophthora, a closer look at the best management practices quickly reveals its application to controlling other pathogens.
The icing on the cake? The researchers have designed a free online course for nursery growers to help them identify and learn to manage Phytophthora diseases in their operations.
