Acer
Klevas (lot. Acer, angl. Maple, vok. Ahorne) – klevinių (Aceraceae) šeimos augalų gentis. Genties pavadinimas kildinamas iš lotyniško žodžio acer – smailus, aštrus, ir graikų kalbos žodžio akros – smailus (klevų lapų skiautės smailiaviršūnės).
Iš viso gentyje yra apie 150 rūšių ir daugybė porūšių. Europoje yra tik keletas savaiminių rūšių, žymiai daugiau jų yra Azijoje, Amerikoje, netgi Afrikoje. Lietuvoje auga viena savaiminė rūšis (Paprastasis klevas – Acer platanoides ) ir dar kelios įvežtinės rūšys.
Klevai, ypač japoniškieji (A. palmatum, A. japonicum, A. shirasawanum) dažnai serga verticilioziniu vytuliu (angl. verticillium wilt) . Šios ligos sukelėjas yra grybelis Verticillum, kuris patenka į augalą per šaknis ir jį užkrečia: staiga nudžiūsta lapai arba visas medis. Infekcija susikaupia dirvoje, jei prieš tai augo braškės, moliūgai, agurkai, bulvės arba pomidorai. Medį reikia iškast ir sudegint ir toje vietoje nesodint jautrių verticiliozei augalų.
Panašius simptomus turi ir bakterinės ligos sukeliamos Pseudomonas genties bakterijų.
Misdiagnosis! Another, fairly common disease that can look like Verticillium is Pseudomonas, or Bacterial Canker. It isn’t easy to tell them apart. A few clues: Pseudomonas often appears in the spring rather than late summer. If you look carefully at the dying limb, you may find a dark sunken area (a canker) low on the branch. The bark on the dying limb will peel off brownish and water soaked, but there will not be the dark streaking of Verticillium. Fall & spring sprays of copper may help prevent Pseudomonas infections.
“There are other pathogens (pseudomonas, phytophthora, etc.) that will cause dieback and wilting on Japanese maples and many times these are confused or mistaken for verticillum wilt . But japanese maples are inordinately susceptible to this problem, perhaps due to their rather delicate, easily damaged root system compared with most other species of maples, and IME, they seldom survive.”
Čia keletas “receptų”, nors, atrodo, išgydyti jau užsikrėtusius augalus bevei neįmanoma, netgi naudojant sisteminius fungicidus. Yra keletas publikacijų apie tai kad ypač vertingus medžius galima išgydyti
“Maintain tree vigor by fertilizing with “balanced” fertilizers (10-10-10 [N-P-K]) and watering. High-nitrogen fertilizers may increase damage.”
“Avoid high nitrogen fertilizers – use balanced fertilizers or fertilizers with slightly higher phosphorus levels. ”
“I had Acer triflorum which I noticed having dieback because of verticillium. In the autumn I did cut most of its growth off leaving only one low branch but there was black half of a ring visible in the trunk. Next spring I washed all the soil off and did major root pruning similar as for Bonsai and planted it to mostly sand with mulch on top.
When it started to leaf out I gave daily watering with diluted urea (which is a form of 50% nitrogen, heaping table spoon to a gallon). Growth was good and this is its third summer and it has had no dieback other than tips which die in winter because they keep growing until first freeze drops the leaves.
I remember reading long time ago that nitrogen is used to heal verticillium affected plants but did not found same article two years ago but tried it anyway. What is there to loose? Of course I was careful not to infect other plants and did root washing far and planted it to far corner as well.
Its original location I dig most soil to trash and then treated hole with a lot of lime which I also remember reading killing verticillium in ground.”
Virtually any resource you find on verticillium wilt on Japanese maples cautions against the use of a high nitrogen fertilizer like urea. And if you think about it, it makes sense – rapid foliar growth can only additionally stress a tree that has a compromised vascular system. An infected tree just doesn’t have the proper, intact internal mechanisms to process and support this type of growth. And nothing I’ve ever read on the subject indicates soil pH (adding lime) has any effect on the pathogen – the VW pathogen can be present under any soil condition, acidic, neutral or alkaline. And since Japanese maples prefer acidic soil conditions, adding lime to the soil would seem counterproductive, as well as having no significant impact on destroying or halting the pathogen.
I’ve noticed that the best way to prevent disease is to give extremely well drained (almost dry) soil. I add large amounts of sand and mound when planting. Acer palmatums planted in clay soil often succumb to various disease which I can not identify. I have had many palmatums that have shown signs of VW and I have ultimately removed them. I have not always seen the signs of a “green/brown ring” inside the stem but I typically remove them if I start seeing the typical wilt of one branch at a time. Usually the plants I have suspected of having VW wilt and die within the time frame of a few months. I have had mixed results with Phyton-27. Phyton does not appear to “cure” VW as it is reported, though it is a great product. I always treat newly planted Palmatums with Phyton and they appear to remain clean. Once VW is evident in a palmatum Phyton does nothing to stop the spread.
- Posted by nikkie_in_toronto (My Page) on
Tue, Jul 14, 09 at 10:39
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.
