Concerned about graft on young maple

I got this young grafted Nuresagi fall of 2011, and while it struggled last year in the heat, it did pull through - the tree would be roughly 3 years old now. However, upon inspecting all my trees today, I am concerned about the graft union on this tree. This is pretty much how it's looked since I got the tree, but it does appear to be a bit 'drier' than what I remember, almost like it's starting to pull apart - and there appears to be very little live wood actually connecting the understock to the graft.

Is there anything that can/should be done about this? I have cut-paste that I use for sealing wounds on my bonsai; should I apply this over the area to keep it sealed? Should I be worried that the tree (ie, the grafted cultivar portion) will not make it?

Any advice would be greatly appreciated!!

 

I have seen that happen when the understock is not cut off properly (flush with the stem). I would cut off the dried "stub" so the bark can more easily heal around it. Other than that, just take care of it and see what happens...

 

Thanks!

My biggest worry, if healthy wood does not increase/grow around the dried, dead portion, is that, as the tree grows, the little bit of live wood connecting understock and graft will A) no longer be able to transport enough nutrients/energy to the tree, and B) the increasing physical weight of the tree may no longer be able to be supported by the small bit of live wood...

 

All the more reason to prune it properly now and let it heal . Do you have a pair of concave pruners? A must for doing this properly.

 

Its raining off and on today, but I will try to get a good shot showing the other side of the union, wherethe wood is still connected and isn't dried up.

I do, and several other bonsai tools. Could you illustrate on my picture(s) what/where to cut? Obviously I only get one shot at this and want to make sure I do it correctly so I don't weaken the tree further...

 

I could be wrong but looks like they've splice grafted a large scion onto the rootstock?

 

More pictures of the graft, from all angles. So, just remove the upper 'stump' of the understock? Or should I be doing something else too?

 

Yes, if you use the concave pruners it should leave a slight depression that will be easy for the healthy wood to cover over.