Thanks Steve, I know that this tree is not in trouble yet, but as I do not know much about benching, my concern is that it will just get worse over the years until it does become a problem. Does benching like this simply go away in some cases? Or will it get progressively worse?

Benching does not ordinarily go away, nor does it ordinary cause a problem. I agree with Steve that the tree looks to be just fine. If it were my tree, I would not worry about it. The benching shown in Skeets picture is VERY common to many thousands and thousands of trees. I think the best advantage provided by in-arching the tree, will be found mainly in Skeets peace of mind. - Millet

How does one explain the decline in production and health of the grafted trees on swingle type rootstocks that only show up after 20 to 25 years? These are from hundreds of trees in various cultivar x rootstock trials.

http://www.plantbiology.ucr.edu/documents/files_of_Roose/rootstock_trial_summaries.html

Look at each of the linked PDF file and where they removed the tree stumps, cut it open and looked at the benched unions, tested for starches, sugars, looked under microscopes and did other morphological studies. It supported that benching is the most likely major cause of the decline and has been shown how the vascular tissues have restricted flow of supplies and nutrients both ways.

But of course what we can do depends upon our objectives of growing citruses. Most of us for example, we expect both apricot and peach trees to be productive but short-lived. But for citruses, I expected them to last over 100 years. But unless you define that your citrus tree will only be productive for 20 years, in which if you have future generations, they would just plow them under anyway, then that is perfectly fine to leave the trees alone.

However, in the face of hard evidences, as to the cause and effect, and how most likely it is the reason, it would prompt me to do something about it because I expect my citrus trees to last a long time.

But as fate has it, none of my multi-graft citruses are on swingle rootstock. So if most likely your trees are not on swingle or on the other rootstocks that shows decline after so many years, then you need not worry. Benching and coupled with decline after so many years, happens only with few rootstock types, not in all of them.

Hello Joe,
thanks for that information.
So it seems only "Swingle" has that problem, other well know hardly benching rootstocks, like Poncireus trifoliata itsellf, seems not to suffer after 20 years....
So it seems best, to avoid only Swingle.... can you agree?

If a tree (any kind) lasts 20 years or more, it will be a good chance it will out last me!

Ned

Interesting how they used iodine stain to track the starch movement. That does appear that it was the swingle rootstock that was incompatible and that the benching there may have just been part of the response, then I guess I don't have anything to worry about. I think the easy fix for my peace of mind will be to graft another Ponkan on that trifoliate rootstock sprout.

From Integrated Pest Management
For Citrus, University of California
Statewide Integrated Pest Management
Project, Division of Agriculture and
Natural Resources, Publication 3303.
in regards to Bud Union Disorders,
page 117.

"Certain scion-rootstock combinations
show an incompatibility reaction, which
appear shortly after grafting or may take
10-20 years to develop. An example of
delayed incompatibility is bud union
crease. A crease or fold forms at the bud
union, and with increasing overgrowth,
the food conducting tissue is compressed,
resulting in a slow girdling of the tree.

When planting or replanting, avoid
susceptible combinations. For example,
Frost nucellar navel on trifoliate, lemon
on Cleopatra mandarin, Eureka lemon or
Satsuma mandarin on Troyer, and certain
scion lines on sour orange develop bud
union overgrowths."

A link is posted below of a photo
scanned in on page 116 from the
same book.

http://users.cwnet.com/snickles/Plants/crease1a.jpg

Jim

Thank you so much Jim for the links!

Dear Joe,
as I do not use benching stocks, I only have once seen such hard benching in an Orangerie here, and those trees did not look very promising nor very pleasant.
It were Citrus medica onto some kind of trifoliate stock, Citrange, Citrumelo or trifoliate orange itself, cannot say.
But here I found that strangulating fold at the bud-union, but: As I talked with the master-gardener at the place, he wasn't obvious about, he was guessing about pest infection and was considering a pesticide application.
So these trees where one year later copped for heating purposes

So it was just, to have an advice for someone, who thinks about... So regrafting/rebudding seems to be the best solution

Thanks.

Rootstocks such as “C35” and “Carrizo” have demonstrated good adaptability to calcarous soils and provide reasonable resistance to fungal rots in combination with good productivity. Sour orange rootstocks should be avoided due to their susceptibility to the tristeza virus and quick
decline disease. The “Flying Dragon” rootstock is used as a dwarfing rootstock and the resulting tree is often used in patio plantings. Rootstocks with lemon heritage, like Rough Lemon, Schwab Rough
Lemon, or Volkameriana, produce fruit that tends to have lower sugar content and less acid producing a bland taste. These rootstocks will produce a tree that grows quickly and produce plenty of large-sized
fruit but the quality of the fruit usually suffers. Macrophylla is a rootstock popular on the coast as a lemon rootstock but is too frost sensitive for many conditions.- Millet