Plant Diseases/Sudden Oak Death
QUESTION: Hi Melissa,
Some of our Coast Live Oaks are showing a starnge dark colored oozing at thebottom of the trunks. COuld this be something serious like Sudden Oak Death? I live in Santa Clarita, California.
ANSWER: Dear Susan, I hadn't heard much about Sudden Oak Death until recently, but then I live in Texas, so we don't have it here, or at least not much. Regardless, your pictures don't look good at all. This Phytophthora disease is a very bad and pretty incurable disease, similar to the other Phytophthora diseases which are also very hard or impossible to cure. One sign would be the dark viscous drainage coming from the trunk. They may live for quite a while even with the disease. You need to evaluate each tree on an individual basis. If they are in danger of falling on buildings then you should cut them down. Otherwise, I would just monitor the trees on an individual basis. This doesn't look like borer damage for several reasons: the sap is thicker, darker, and the scorching on the tree looks like the Sudden Oak Death symptoms. Also you have no frass or wood shavings from borers and no holes. The only other thing this damage looks like would be lightening strike or similar physical cause. Unfortunately, the only way to determine for sure if this is S.O.D. is to take bark samples to a laboratory and have the pathogen identified. In the long run, it won't make much difference. Cut the trees down when they become dangerous. If you wish to make a clean sweep, you could cut them all, but you should wait a while to replant, and then you should go with another species. In the meantime you would lose the shade. I am sorry for this unfortunate news, but at least you can be prepared. Please write back if you have further questions. Good luck, Melissa
---------- FOLLOW-UP ----------
QUESTION: How is Phytophthora treated? Any clue? I have zero idea why these trees have been getting "treated" for the last 4 years. What's the point?? My landscape operations manager told me that is what the trees have....just like what you said. :-(
ANSWER: Dear Susan, There is really nothing that you can do when Phytophthora strikes. It's name in Latin means "plant destroyer" and that is exactly what it does - destroys plants. In every form that I have seen it, it is very lethal. When I did some work for local nurseries, it was a real problem when you received shipments of plants that came down with Phytophthora. One of the main culprits were the Vincas or periwinkles. They would almost immediately wilt out of nowhere. I suspect that the aggressive nature of this pathogen causes the plant to cease uptaking nutrients and water very quickly - in which case even strong systemics would not work because the plant can't take them in. And there really isn't anything that you can do to systemically treat an oak tree. Unless it's very young it's simply too big to be affected. I am very concerned about what possible treatment your landscaper has been treating them with; you may very well have a case of malpractice on your hands. In any event, despite looking through numerous reports from agricultural agencies, I see absolutely no treatment for Phytophthora once the tree is showing the oozing and scorching signs. There does seem to be some sort of product for the prevention of the disease, but once the tree is badly damaged, it's really a matter of when you want to take it out. If it's the only oak and you have little shade besides it, you might want to plant a non susceptible tree and cut this one down at some point. You would cut it down sooner if there are signs of it falling. If you have many oaks and this is the only one infected, then cut down the tree and treat the others. I would ask your landscaper to show you what he uses to treat the oak with, and read the label yourself. Unless it is actually listed for Sudden Oak Death, then you should tell him you aren't paying any more. I hope this information helps you. Good luck, Melissa
---------- FOLLOW-UP ----------
QUESTION: There are 8 trees that are oozing. I demanded pathology be done on half the trees along with soil samples.I briefly spoke to an arborist. I guess in Southern California it is most likely Phytophthora Cinnamomi. Any clue if that is as close to lethal as SOD???
Dear Susan, I doubt that you are seeing Phytophthora cinnamomi just because you are in the southern region of California. This strain of Phytophthora attacks fir, spruce and cedar, but I don't see oak listed for it. Regardless, your symptoms are that of sudden oak death which comes from the Phytophthora ramorum. The particular strain of disease could be identified in a lab, but that may be an unnecessary expense. All of the Phytophthora diseases are very lethal. They cause such immediate system failure that there is really no way that the plant can be treated. I'm sorry you have such a devastating disease to contend with and I wish you luck. Melissa