Friends: I have several japanese maples with, I believe, verticillium wilt. They are losing branches one by one. I have read many threads here, but many are old. What is the latest treatment for this evil? It may be too late for my two trees, but I am willing to try most anything. Thank you, Richard, Santa Cruz, CA
There are no new techniques for fighting off the two forms of Verticillium that are prevalent in Maples. The lethal form has no suppressant other than not to buy from that grower/seller. This form is known as the quick decline form and as soon as the Maple starts the decline the game is over. The whole plants shuts down seemingly all at once and there is nothing we can do for it. What you have is probably the more common form of Verticillium usually brought about by stress either from lack of water, too much water, too much sun and not enough water, too much fertilizer and not enough water. We deal with this form by pruning the branches out that appear to be dying right before our eyes. All Japanese Maples have some amount of this form of Verticillium in them. It is passed from parent to parent. In other words any and all grafted Japanese Maples have this pathogen in their system due to the pathogen being in the parent, in this case the scion parent. Acts very much in this respect like Bacterial canker (Pseudonomas syringae) does in Fruit Trees. The bothersome aspect for me of Verticillium is that I've seen much more evidence of Verticillium in the rootstocks coming out of Oregon that I ever have before. Not only are the scion parents dirty but so is what appears to be a wide range of the rootstock. Obviously grafters are not paying attention to their rootstock culture and selection but this is not new as there were a few individuals around in the mid to late 80's that had dirty rootstock then. There are some fungicides that right on the label state they can be used for Verticillium. I've always felt this was a misnomer as the pathogen that they are referencing as being Verticillium is a form of Pseudonomas instead. Verticillium in the plants system to start with cannot be effectively controlled. Aside from the lethal form we do not lose our Maples solely due to this form of Verticillium, we lose the plants because of us and our growing techniques or lack or care for the plant before and after the plant stresses. Without stress the Maple will generally show little effects of the disease but once the plant stresses we will see it. Another thing to remember is that certain varieties of Japanese Maples are more prone to show the effects of this disease than others will. The only way to help ourselves is to quit buying the names of the Maples but spend more time on the selecting for the quality of the plant itself. Buying a run down Maple at a giveaway price is no bargain as that plant will take some real babying to nurse it back to health and sustain that healthy condition if it ever gets there. Too many times we bought a mistake that a nursery was selling, feeling chipper the whole way home with it and then see the Maple die out within three years for us. We knew in advance there was a reason why the wayward plant was so cheap, we rolled the dice and just like the odds are of winning we lose more often than we will win. I started a thread on Red Filigree Lace in which I showed my plant that was going to be a goner quite soon. This Maple grew very well for me for several years, much longer than most people have had a Maple in this forum. The plant started to stagnate meaning the Maple would put out Spring growth but then did not put out any new growth for the rest of the year. That was my stormbringer of things to come and I knew it dealing with Maple that was notoriously dirty in the nursery trade for many years. I got some dieback on the plant and pruned it back to live wood hoping that the plant would send out some new growth but it did not. So, in three successive years of pruning the dead wood out I kept getting less and less Spring growth and then the Maple finally succumbed to the Verticillium that was already in the plant. The plant just could not regenerate enough new growth to supplant the older growth that it was losing. The plant essentially gave up and that was that. What you need to do is start pruning out the dead and dying wood right now back to live wood. Make sure these Maples do not stress any more as continued stress, even in what we felt were "clean" (the antithesis of dirty) Maples can show the ill effects of Verticillium upon stress. If you read the Fireglow threads you will know that my Maple undergoes a complete burning of the leaves every year once the temps get into the 100's for a week. If that Maple was or were to die on me due to Verticillium it would have already done that years ago. I am dealing with a clean Maple as a result as I get no real branch dieback from the loss of all of the leaves. That is one experiment that came out to my liking. Jim
I am very interested in verticillium wilt, partly because I suspect I have it in my own soil and partly because I work at a retail nursery. One customer came in lately with a Japanese maple sample that we thought probably had it and she sent a sample to the Washington State Extension Service to have it confirmed. It was verticillium wilt even though it did not have the brown streaks in the cambian layer that is often a symptom. The tree was many years old but died quickly. No growing conditions had changed and it had never had any die-back before. She does buy compost and mulch with it every year. Could the lethal strain have come in with that? Does the lethal strain have a name? If you have it, should you not plant anything susceptible in the area? Does it spread easily to the rest of the garden? I must admit I am pretty concerned about the fact that a lot of Japanese maples carry this fungus in one strain or another. Thank you for this information. I had suspected something like this. I don't know if I feel right recommending them to customers knowing they have this fungus. We sell a lot of them in our nursery and they look very healthy, but I don't want to infect customer's gardens. Is it widespread or a native fungus, enough so that possibility of introducing it into their yards isn't a major concern? What are the varieties that are more susceptible? I don't know if you feel right in telling, but if you do, who grows clean stock? I can understand if you don't. I have had many plants show signs of it over the years, and a few have died. Who knows, I could easily have a phytophtera too, I should have it tested to tell for sure. My latest worry has been my large Dove tree that has had shown the yellowing branches on one side of the tree in summer symptoms like verticillium wilt. So far I haven't seen it yet, I hope it has compartmentalized the fungus for this year. I would hate to lose it, I grew it from a gallon pot. I read that ammonium sulfate can help, what do you think of that? I have my doubts, I did buy some last year but haven't tried it yet.
For more about verticillium wilt of maples: http://plant-disease.ippc.orst.edu/disease.cfm?RecordID=715
I have not detected any verticilium-like symptoms in any of the maples I have in the ground. However I have problems with some maples still in pots that may be due to it. Since I do not know for sure I would like to benefit from the experiencxe of those who, unfortunately, have been confronted with it. It is my Taroh yama which was splendid in the spring (see the post I placed in the Gallery: Taroh yama). However in June it started to decline, leaves would shrivel in the edges and some would fall. No new growth and the end limbs have started to change color from green to reddish brown. I have pruned off one branch (see pics) and it looks good with no discoloration in the vascular system. What do you think?
Hi Gomero, You need to show us a cross section of the branch so we can see what's happening *inside*. When you cut the branch that is suffering from verticillium, but not dead yet, and look at the inside you may see a dark circle or band where the xylem layer should be. The verticillium clogs this vascular layer that transports nutrients and moisture to the leaves and branches. Usually you'll see this banding on a main branch or trunk and not so much on the outer branches even though it's these outer branches that are affected the most. FWIW, I have a tomato plant that I suspect has verticillium. One of the main branches coming off the trunk started looking real bad. I cut it and saw the telltale dark ring. The other branches don't look as bad but they're showing typical "tomato" verticillium signs...yellowing leaves eventually drying up from the base on up. I may have to toss it. I'm also watching my Butterfly as it too seems to have verticillium symptoms, though it could just be adjusting to it's new hotter, sunnier surroundings. The best thing you can do with regards to maples is to prevent the fungus from getting a foothold in your tree. Pathogens are everywhere and like us plants will succumb to them if their health is compromised. If they are healthy they have a better chance of staving off the disease. That means keeping them properly watered and fertilized. Layne
