It is always advisable to first have a tree tested before removal to be sure P. ramorum is present. If you are noticing symptoms in spring, attend a nearby SOD Blitz for information on sampling and lab submissions. For more information, go to sodblitz.org.
When trying to determine if an oak may have SOD (caused by the plant pathogen Phytophthora ramorum), the first step is to determine if the tree lies within 1 km of a known outbreak. This can be done by accessing SODMAP at www.sodmap.org or by uploading the free “SODMAP Mobile” app to your smartphone. Stand next to the tree in question and tap the risk button. A response of moderate or high risk would suggest Phytophthora ramorum may be present. The next step is to confirm it is indeed P. ramorum. Make sure the oozing is not wetwood, or bacterial flux, which typically is associated with much more oozing and often has an unpleasant odor. Bacterial flux usually has a watery secretion running down the trunk that originates from a wound or branch crotch. If all symptoms align with SOD, the next step is to test for P. ramorum. If a symptomatic California bay laurel tree is within 10 m of the oak, collect symptomatic bay leaves for testing. This is not a definite diagnosis for the oak, but it may be an acceptable one that does not involve wounding the oak tree for sampling. Bay-based diagnosis for an oak may be less accurate after multiple years of drought, as bays may actually turn from SOD positive to SOD negative during extended dry conditions. One can get bay leaves tested by participating in one of the annual SOD blitzes (www.sodblitz.org) or by submitting samples to the California Department of Food and Agriculture. Testing the oak requires debarking a portion of the tree until the margins of the putative SOD lesion under the bark are visible and then plating the margins of the lesion on Phytophthora-selective medium for laboratory analysis.
SOD Blitzes include a training session for blitz volunteers on SOD and proper sampling, followed by time in the field for collecting and marking sample locations. All necessary collection materials are provided to volunteers during the training session for use either the same day of the training or the day after. All samples are to be dropped off at a designated location (location announced at the training session). There are approximately 20 SOD Blitzes in areas of California that have sudden oak death or at risk of disease establishment. Most of the training sessions are offered on Saturday mornings. SOD Blitz schedules for the coming year are posted annually during the last week of January at www.sodblitz.org.
Oak testing is routinely done by arborists. It is a rather involved and tedious process that requires a fair amount of finesse and know how as it entails wounding the tree by shaving off the outer layer of bark to collect infected tissue. If you decide to have your oaks tested for SOD, consider going to the Trained Professionals List for arborists that have recently attended an official SOD seminar (Not intended to be a list of recommended professionals, this list does serve as an additional filter when trying to identify arborists that are up-to-date on the latest science-based SOD information.).
Alternatively, a less invasive method of determining the presence or absence of SOD on your property is to sample symptomatic bay leaves (See Hosts and Symptoms for SOD symptoms.). Keep in mind that any infested bay in the general vicinity (typically within 200 ft of an infected oak) may be the inoculum source for infection of your coast live oak. If bay sampling is your preferred method for pathogen detection, you can call your local UC Cooperative Extension office to find out if the California Department of Food and Agriculture is processing leaves from your county and, if so, what the protocol is for sample submissions. In lieu of submitting samples through your county, you can go to www.sodblitz.org to find out when a SOD Blitz will be held in your region (Dates for each year are posted by January 30th. Blitzes typically occur from March to June). Attending a blitz will afford you the opportunity to learn more about SOD, including the latest disease control strategies, during a 1-hour training session. At the end of the session you will be given all sampling materials and instructions for submissions. Blitz participants are free to submit as many leaves as necessary, meaning that you can send in all suspicious leaves from your property as well as from the neighborhood or nearby local parks. All leaves are processed at UC Berkeley and all sampling results are published in a database available at www.sodmap.org or through the free App SODmap mobile.
This beautiful mushroom, the rosy bonnet (Mycena rosea), collected and described by amateur mycologist Giovanni Robich, is vouchered in the herbarium of the Museum of Natural History of Venice, Italy. In fact, the entire herbarium is curated by expert volunteers. UC Berkeley, NCBI, and CBS researchers have sequenced a DNA barcode for most species in the museum and have devised an approach to test the validity of the taxonomy curated by volunteers, showing these volunteers perform as academic researchers.
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