kaki sudden death syndrome revisited

creekweb(6,7)June 4, 2013

At this time of year in my orchard, as in years prior, the surviving kaki persimmon trees stricken with this disease show the symptoms - vigorous growth full of blossoms that appeared over the previous few weeks die off in a matter of days. This year a tree which had not previously shown symptoms has developed a full blown case and provides some valuable clues as to the likely origin of the disease. The scionwood I know to have come from a tree that had withstood many cold winters over many years and as such would be unlikely to be harboring latent viruses, as they previously had ample opportunity to have caused disease. This points to the rootstock, the variable factor here, as the likely culprit. Whether the causative factor is infection or incompatibility is unclear but arguably of lesser importance as nothing much is to be done about either.
This observation leads to a few recommendations:
1) Choice of rootstock is key. I would think proven cloned rootstock gives the lowest chance of disease.
2) Once a tree shows signs of disease, the rootstock is implicated and it's a goner. Best to cut losses here and replace or regraft to American persimmon.

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Tony(Zone 5. Omaha, Nebraska)

Creek,

How many of your persimmon trees are infected? Do the leaves show dark veins?

Tony

This post was edited by tonytran on Tue, Jun 4, 13 at 17:04

    Bookmark   June 4, 2013 at 3:25PM
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creekweb(6,7)

Tony,

I currently have 2 trees affected and have lost 2 in the past to the disease, one of which I regrettably grafted back to kaki and the other to virginiana. If you pay close attention this time of year you will first note the blackened leaf veins and then rapidly the loss of leaves starting from the ends of new growth. The rapidity in which this occurs throughout the tree calls to mind what I'd expect of an exponentially increasing viral load with resolution (or death) following shortly thereafter, maybe corresponding to the response of the tree's immune system.

    Bookmark   June 4, 2013 at 4:41PM
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Tony(Zone 5. Omaha, Nebraska)

Creek,

So rootstocks may carry the virus. But what about multi-grated kakis on kaki interstem but the rootstock is D.Virginiana? ( I have a 90 chromosomes D.V. rootstock, I then grafted Nikita's Gift on it. Two years ago I grafted Honan Red, Sheng, Tam Kam, and Saijo on the four branches of the NG). I will have to keep a close eye on this tree.

Tony

    Bookmark   June 4, 2013 at 5:34PM
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creekweb(6,7)

My post is speculation - I don't know that a virus is the causal agent, though evidence makes it seem a likely suspect. My observation suggests a problem with the rootstock but doesn't rule out involvement of the rest of the tree. So it may be that a commensal virus of the rootstock becomes distributed throughout the tree in a latent form. If scions are taken from this tree and grafted elsewhere, it is possible that the viruses will later become active and the signs of the disease will be expressed. So the problem with your multi-grafted tree is that there may be a higher chance of infection since any of the scions could have brought latent virus to the tree,

    Bookmark   June 4, 2013 at 8:16PM
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shane11

This is a very interesting thread. It seems there are several theorys out on the cause of this problem. Your theory certainly sounds plausable. I have lost several in the past to this problem all grafted on virginiana.

    Bookmark   June 5, 2013 at 1:41PM
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