Sudden Oak Death

November 11, 2008

The Town held a meeting in September on the important topic of Sudden Oak Death and how it affects, and will be affecting, our Town. You can watch the meeting on Mootube and see our previous article here. Denise Enea, the Fire Marshall for the WFPD, Matteo Garbelotto, an environmental scientist at UC Berkeley, and Katie Palmieri from the Oak Mortality Task Force and a salesman for an Agri-Fos™ dealer, a fertilizer that helps prevent SOD, were available at the meeting, as was fire expert and ‘arborculturalist’ Ray Moritz.

Matteo Garbelotto lead off discussion by describing what has been happening since the SOD Blitz event held in our area in April. The SOD Blitz was held to collect leaf samples to track the distribution of Sudden Oak Death in our region. 26.7% of samples (taken from bay laurel, an important reservoir for the disease) were infected with SOD. Of course, as Mr. Garbelotto pointed out, these samples were self selected by volunteers, so it’s likely that the overall disease rate is lower. Portola Valley and Jasper Ridge were more infested than Woodside proper (you can see the map distribution on the video on Mootube). He stated that the sampling process was not systematic.

The results of the SOD Blitz were available on Mr. Garbelotto’s website. The Woodside (and Portola Valley) results are there and show amoung other things that of 206 samples taken 26.7% of the them tested Positive.

After the initial presentation of his data, several people had questions. Some questioners seemed to be quibbling with the overall methodology. Others seemed genuinely frightened. Unfortunately, Matteo did not give many reasons to be comforted. Instead, his information was pretty scary – strongly implying the devastation of our oak forest within the infected area.

According to Mr. Garbelotto, despite the many dead trees we can see around Woodside, there actually hasn’t been a bad year for the spread of SOD since 2005-06. To spread the disease, trees need to be wet for more than twelve hours and warmer than 19 degrees Celsius. This hasn’t really occurred since then, so the extent of SOD in our area – extensive though it is – is all from that period. During the next warm, wet year, even the areas currently free of SOD will almost certainly become infected due to the distance SOD can travel in a year. The life cycle is that bay laurels and tan oaks are infected the first year and then coast live oaks are infected the next.

The news continued to be mostly grim throughout the meeting. The arborculturalist warned about increased fire dangers from dead trees, as did Fire Marshall Denise Enea. In studies, 40 – 44% of infected live oaks died. There are some things you can do to protect your trees, but protection of large forested areas may prove impossible. Some tips:

• Stay alert. If bay laurels or tan oaks are infected in your area one year, you have a one year window of opportunity to try to protect your live oaks. Consider removing bay laurels and tan oaks within fifteen feet of your live oaks which keeps the spores from spreading as easily. It is not recommended that you removing all of your bay laurels and tan oaks. Bay laurels, while infected, will not die from the disease. If you remove your bay laurels and then your coast live oaks die from SOD, you could be left with a completely bare landscape.

• Concentrate on saving what you consider to be “high value” live oaks. Application of a fertilizer, Agri-Fos, helps protect against infection by strengthening the tree. Once SOD is present in your local area, you need to reapply the Agri-Fos every single year. Injections of Agri-Fos are more effective than external applications, but you don’t want to inject every year due to the wounds you create in the tree.

• Be careful when you prune, since pruning at the wrong time of year can encourage infection. While there are no rules about moving infected materials, it is a very bad idea to move infected or possibly infected materials that can further infect currently clear areas. Dead trees should be pruned before they fall and block roads. However, either mulch in place on your property or contact a company licensed to dispose of infected material.

The meeting ended with a strong message that SOD is “everybody’s problem. There are no barriers to infection between properties. There is some hopeful news. Apparently, there is a close cousin of the live oak that is more resistant to SOD. If you need to replant, that is probably the wiser choice of tree. Additionally, further investigations into treatment and prevention are ongoing.

We strongly encourage everyone to watch the video at Mootube and check out Mr. Garbelotto’s website for more information, and do what you can to protect our landscape and your property.

For more information:
California Oak Mortality Task Force here
Town of Woodside here.
Berkeley Education here.

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