Dieback on JM...

[fredman]

I did a layer on this JM osakazuki this season, but now I'm worried the dieback might kill off the whole tree. It seems to have stopped above the new growth but on the one side it looks like its continuing down. I don t mind the loss of the two branches as I will be rebuilding it in any case. I just need the dieback to stop right where it currently is....!!!
What should I do? Winter is approaching here and I fear it might get worse. Do I leave it and hope for the best? Do I remove those two branches and treat with something?
I'm currently feeding it ferociously to try and strengthen it, so it can fight the dieback...

This is a view from the one side.


This from the opposite side


It seems to growing fairly strongly as it even has a seed pod and flowers on it. Maybe its just confused...
Here is some more pics...

 

[0soyoung]

Acer palmatums inevitably die back to a node. It is a combination of photosynthate flow in the phloem (inner bark) and auxin (hormone that signals life above) flow in the cambium. Keep those (upper) branches alive is about all you can do, as far as I know. I've been shocked at what can happen, but nevertheless, the dieback always stopped at a branch.

 

[fredman]

Thanks for replying Oso
Yeah I hope that will be enough growth to keep the dieback in check. What worries me is the new growth is young, fragile and hopefully enough... I figure for now all I can do, is give it lots of sunlight and keep the feeding up until it drops its leaves. It doesn't make sense removing the dead parts now....? Am I right in saying that dieback is more prone to accelerate in winter?

 

[0soyoung]

Yes, the dieback will become more pronounced over the winter. A few nodes on the shoot makes a strong enough branch to have the dieback stop like it did with my a. palmatum. So, I think you figure right.

I don't think there is anything to be gained by removing the dead part now, unless it just bothers you having to look at it. Almost certainly, you'll end up cutting/carving off some more next spring, anyway.

 

[fredman]

Thanks again

 

[0soyoung]

You are welcome, @fredman.

 

[fredman]

Another question if I may...
What would be the best practice in winter, to increase its chances against the dieback spreading further? I believe keeping it dryer in winter helps...? Anything else?

 

[sorce]

dryer

I don't think so....cuz it's not rotting.

Seems like that could just make you underwater it.

You might end up worth a pretty long season, I think you'll be alright!

Sorce

 

[markyscott]

Couple of general points about Japanese Maple culture. They do not like wet feet and they are not heavy feeders. Both can be obviated with a coarse-grained inorganic substrate, but if you go heavy on organics you have to be more careful with both your watering and fertilization. Both too wet and too heavy fertilizing can cause dieback.

The other thing that can cause dieback is verticillium wilt - is it present in New Zealand? Perhaps it was introduced through the layer? Are the layers doing ok? Or is this one of the layers? You can check for verticillium wilt by cutting off one of the infected branches and checking the sap wood. Infected sapwood will be discolored - like this:



On the left are maple stems with healthy sapwood. On the right, the brown vascular discoloration is a telltale giveaway for verticillium wilt (picture from http://www.apsnet.org/edcenter/intropp/lessons/fungi/ascomycetes/Pages/VerticilliumWilt.aspx).

To prevent, this or other infections that affect JM, make sure that you use good quality sharp tools and make clean cuts. Do not crush the branch when you make pruning cuts on large branches - use a small fine saw instead. And seal all pruning cuts completely with Top Jin or whatever is your favorite liquid cut paste. To be safe, wipe down any tools you use on this tree with alcohol before using them on another.

Finally, a question for you - what happened to these leaves?



They look as though they might have been cut off? If so, don't clip off any more leaves. If they fell off on their own, what happened?

On the bright side, assuming you can return the tree to healthy growth, this may turn out to be a happy accident. Before you had a bunch of long, straight, taperless trunks. Now you have the beginnings of a trunk line with both.



I think that something like the would have had to be done in the long run anyway. Sometimes there are happy accidents. Anyway, first order of business is to get the tree health again. Good luck!

 

[fredman]

The other thing that can cause dieback is verticillium wilt

Markyscott. Sorry for the late reply. Took a while for me to get over the shock and realisation that you most probably identified it right. It never occurred to my that it can be verticillium wilt...
Whenever I hear of that decease I get the cold shivers. Read a few times of the advise given to just give up, and burn the tree in question. I'm definitely not going there yet....
Yes this is a layer that came off this growing season. The layer was made in bonsai soil with chopped sphagnum mixed in. Those leaves (circled in red) were wilted and I removed it.


Others fell off while others came off when I touched it. There are quite a few on the tree now, and the tree looks "stabilized" (for what its worth). Its making new leaves here and there, though they are sort of distorted. The layer is also making seeds on four different places over the tree. I since removed all of them. The tree wants to grow even though its late in the season.



Its a soil born disease, so that might mean that when I bought the tree two seasons ago from the nursery, it had the disease in it. My plan was to layer off the top and then use the bottom for development of another tree. Now looking at the mother tree, its leaves are also wilted....not all but quite a few. It might just be that it is sunburnt, but I doubt that as its a very hardy cultivar (against sun and wind)
Here is some photos of the mother tree...



Problem is to identify it 100%, I have to cut off a piece (on the layer side) and see what the cambium looks like. I don't want to remove any of the "healthy" parts now. As is there isn't any unhealthy sections to remove now, so I guess i'll just have to sit it out.... wait and see what happens come next spring...?

 

[markyscott]

Markyscott. Sorry for the late reply. Took a while for me to get over the shock and realisation that you most probably identified it right. It never occurred to my that it can be verticillium wilt...
Whenever I hear of that decease I get the cold shivers. Read a few times of the advise given to just give up, and burn the tree in question. I'm definitely not going there yet....
Yes this is a layer that came off this growing season. The layer was made in bonsai soil with chopped sphagnum mixed in. Those leaves (circled in red) were wilted and I removed it.
View attachment 99380

Others fell off while others came off when I touched it. There are quite a few on the tree now, and the tree looks "stabilized" (for what its worth). Its making new leaves here and there, though they are sort of distorted. The layer is also making seeds on four different places over the tree. I since removed all of them. The tree wants to grow even though its late in the season.
View attachment 99379


Its a soil born disease, so that might mean that when I bought the tree two seasons ago from the nursery, it had the disease in it. My plan was to layer off the top and then use the bottom for development of another tree. Now looking at the mother tree, its leaves are also wilted....not all but quite a few. It might just be that it is sunburnt, but I doubt that as its a very hardy cultivar (against sun and wind)
Here is some photos of the mother tree...

View attachment 99377 View attachment 99378

Problem is to identify it 100%, I have to cut off a piece (on the layer side) and see what the cambium looks like. I don't want to remove any of the "healthy" parts now. As is there isn't any unhealthy sections to remove now, so I guess i'll just have to sit it out.... wait and see what happens come next spring...?

Well, when I saw the missing leaves I wondered. Leaf scorch and verticillium wilt look pretty similar and can cause premature leaf drop. But when you have leaf scorch and branches are dying back, my mind goes to the disease. You might be able to take a branch in for testing if you have whatever the equivalent of your local ag extension is in New Zealand.

Do you keep it in the full sun?

 

[fredman]

Yes it was in full sun until I separated it. The last 4 months its only been getting morning sun.
Yes NZ has got a huge problem with the disease. The kiwi fruit industry lost more than half its producers because of it. They are slowly coming back I hear. Planting different strains I believe.

I read that the disease does go in remission sometimes. You know if the tree can overcome it to? Is there hope that it might be freed from it in future, or does it only stay dormant under good horticultural practices?