Hi Marten. I live in East Texas and grow about 20 different kaki cultivars, all grafted on DV rootstock. About 3 years ago I had a 15’ tall (4” trunk) commercially-grown Saijo suddenly wilt and die clear to the ground (but dozens of DV rootstock suckers are still coming up around the stump). A nearly identical Saijo tree just a few feet away (their canopy branches actually interspersed each other) was fine (symptomless), and still is. I had recently added a few twigs of other kaki cultivars to a few branch tips of the tree to preserve them until my DV rootstock reached grafting size, and I attributed the sudden death to an introduced pathogen (SDS?). I have subsequently grafted quite a few different kaki cultivars on DV seedling rootstock, and found that several of my Saijo grafts will be growing vigorously and suddenly die. Still not sure why, but Saijo seems very susceptible to sudden death. No such trouble with any of my other ~20 cultivars.
I should add an interesting bit of information. One of the cleft grafts I had recently top-worked on the Saijo was Fire Crystal. The entire Saijo tree was essentially completely dead, but the 1-year old Fire Crystal branch was fine! And it was about 6 feet up the Saijo tree at the tip of a now completely leafless Saijo branch. If the Saijo trunk floam had collapsed, I would have thought the Fire Crystal would have died too. I decided not the try to “rescue” the Fire Crystal branch tip by grafting it on another tree for fear of moving the pathogen to that tree.
@Johnsgard – This seems to indicate that the Saijo tree is not completely dead. For some reason it shed its leaves but the roots and circulatory system are still working. If Saijo’s buds are still viable, maybe it will bounce back.
This is entirely speculative but maybe the tree is smart enough to shed leaves to prevent the spread of infection. Don’t give up hope.
Unfortunately my large Saijo is most profoundly dead. Shelf fungi emerged from base of trunk and it eventually snapped off entirely just below the graft line. My reading about sudden Kaki death indicates that DV is a symptomless carrier for the viroid. I have been quite worried about the rest of my Kaki orchard ever since loosing that first tree.
The whole sds thing is one of the reasons I’m afraid to grow an Asian on my land. I’m in the DFW Texas region which is part of the southeast region.
I wonder if hybrids have better luck surviving sds, because I would love to have a Jt-02
UPDATE April 24, 2024.
Saijo looks done for. The trunk still has green cambium, but last year’s growth is brown and dead:
My remaining Saijo is about 50 feet away and appears totally unaffected.
Nikita’s Gift appears to be doing a death rattle:
Note the black streaks in NG’s leaves:
The Fuyu is getting worse, also, but not quite as rapidly as Nikita’s Gift:
Not every leaf is affected (yet), but those that are appear to be randomly distributed (not limited to any scaffold) and in severe condition:
Nikita’s Gift is a hybrid, and if what I am describing here is indeed kaki SDS, it is definitely not immune.
If the problem is somehow related to D.V. rootstock, I wonder if I could try D. kaki rootstock. Lotus is not a good rootstock for the east coast – it seems to want to leaf out too early.
If it is a rootstock incompatibility between a kaki and DV instead of a pathogen which causes the decline, I wonder if anyone has tried a double rootstock graft to see if that helps. By that I mean grafting a lotus into a dv, and ontop of the lotus graft the kaki. Of course I have no idea if a lotus on dv would be less likely of a rejection, and the same with kaki on a lotus.
I’m wondering if the SDK problem is most closely related to whether 60- or 90-chromosome DV rootstock was used. Has this been looked at? All of my grafts on rootstocks from one northern source have worked well, while a single tree from another source had three of four grafts fail. (The one that worked was a DV.)
Not by me.
I am pretty confident that all of my kaki, including the ones dying of SDS/whatever, are on northern (90) D.V. rootstock (except for one that is on lotus), because I ordered them all from online nurseries. Also, I think I remember seeing a residual DWN tag on one or two, and DWN uses northern rootstock.
Edit: To be clear, the tree on lotus is not dying, but it is about 1500 feet away from the stricken trees and is planted close to two other kaki on D.V., neither of which is dying.
The symptoms look consistent with SDS, at least as depicted in this paper.
Rootstock-scion incompatibilities are often pathogen related, especially when you have such a rapid decline of the scion. Usually, the rootstock is resistant to the pathogen while the scion is not, and the immune response of the rootstock to the pathogen ends up disrupting the flow of sap through the graft union.
From the paper I linked above, the symptoms appear to stop at the graft union, which is pretty consistent with pathogen-induced graft incompatibility.
In kiwi, diploid, tetraploid, and hexaploid rootstock-scion combinations appear to have no effect on compatibility. That seems to be the case for citrus as well. I would be surprised if ploidy had any major effect on graft compatibility for any plant. You could have differences in scion vigor though.
That said, given that all DV rootstock is non-clonal, and the species has a wide distribution, it’s possible that different populations of DV have different susceptibilities to whatever pathogen is causing SDS, whether it’s Xylella or a virus or combination of pathogens.
This is pretty depressing. Just to understand my required response – Based on the article linked above, it seems that the bacterium Xylella fastidiosa is responsible for SDS. This bacterium is mainly found in the southeastern U.S. (with some CA and midwest). I assume that the bacterium can be transported elsewhere either in (1) infected rootstock trees; or (2) grafted trees on infected rootstock. If a tree is affected outside the southeast, what are the right steps to eradicate the bacterium locally?
I assume we should burn affected trees. What else?
A different strain of the same bacterium causes Pierce’s disease in grapes. It’s limited by winter cold. A cold winter can eliminate it, usually below 10F for several hours. SDS likely has some type of cold limit as well. I haven’t heard of it occurring here in middle TN, but we also don’t see much Pierce’s either. However, Pierce’s is creeping up into southern TN, so I wouldn’t be surprised if SDS is too. Since it’s asymptomatic in D.v., it could easily go unnoticed.
It’s a pretty impressive bacterium in terms of number of species that can host it… from the wiki page:
Host species
X. fastidiosa has a very wide host range; as of 2020, its known host range was 595 plant species, with 343 species confirmed by two different detection methods, in 85 botanical families.[34] Most X. fastidiosa host plants are dicots, but it has also been reported in monocots and ginkgo, a gymnosperm. However, the vast majority of host plants remain asymptomatic, making them reservoirs for infection.[citation needed]
Due to the temperate climates of South America and the southeastern and west coast of the United States, X. fastidiosa can be a limiting factor in fruit crop production, particularly for stone fruits in northern Florida and grapes in California.[25] In South America, X. fastidiosa can cause significant losses in the citrus and coffee industries; a third of today’s citrus crops in Brazil has CVC symptoms.[29]
X. fastidiosa also colonizes the foreguts of insect vectors, which can be any xylem-feeding insects, often sharpshooters in the Cicadellidae subfamily Cicadellinae.[3][21] After an insect acquires X. fastidiosa, it has a short latent period around 2 hours, then the bacterium is transmissible for a period of a few months or as long as the insect is alive.[citation needed] The bacterium multiplies within its vectors, forming a “bacterial carpet” within the foregut of its host. If the host sheds its foregut during molting, the vector is no longer infected, but can reacquire the pathogen. At present, no evidence shows that the bacterium has any detrimental effect on its insect hosts.
It sometimes causes symptoms in avocados, apparently, so that’s something new for me to worry about!
I’m really sorry to see your pictures, and I feel your pain. I’ve lost a dozen or so kakis and hybrids to this, and it always seems to hit around this time of year when the trees have put out an initial flush of leaves and look healthy. It starts at the tips of a few branches and works its way down the tree. Sometimes the trees survive one year only to succumb the next. I’ve had trees that were 4 or 5 years old and produced baskets full of fruit die within a few weeks. The D. virginiana rootstocks survive, but no kaki or hybrid graft that I’ve ever subsequently tried on them will grow beyond a few weeks. The scions will put out some leaves and look like they’re going to make it only to wither. I’m not sure it makes any sense here in the Southeast to destroy the infected rootstocks because we’re surrounded by wild trees that presumably carry the same pathogen. Initially I dug them up and burned them, but a few I’ve since regrafted with named D. virginiana cultivars that have grown well and produced fruit. I was so discouraged the first time I lost one of my older kaki trees, but now I just try to keep planting a couple young kakis every year to replace any that die (on average about 1 or 2 a year). Kakis bear relatively early and are such productive and low maintenance trees, that it’s hard to justify giving up growing them entirely just because a few will die suddently and unpredictably. I now look at them as a perennial fruit crop that needs regular replacing. We probably aren’t going to get the 100+ year old kaki trees here in the Southeast US unless some cultivars are resistant. I’ve lost Saijo, Sung Hui, Giombo, Tam Kam, Hana Gosho, Kasandra, Coffee Cake, Miss Kim and probably a few others. My oldest tree that never got infected was Tecumseh (though I eventually had to cut down that particular tree after 11 years to make room for a new septic drain field). I hope your other kakis survive and you don’t lose so many again in the same season. Growing fruit isn’t for the faint of heart!
Hi @ncdabbler , would you know if the SDS affects kaki grafted onto D. Lotus rootstock?
@GrapeNut mentioned above “the immune response of the rootstock to the pathogen ends up disrupting the flow of sap through the graft union.”
I wonder if D.Lotus and Kaki have would have such a drastic response to the pathogen as DV+Kaki Combo.
Thanks for this report, @ncdabbler. This sounds very similar to issues I have had. I also tried many times to graft on the stocks and it never worked. Right now I unfortunately have my only two mature trees left in decline; four or so are already gone. I did start putting in completely new trees a few years ago so hopefully those will be going strongly before the older trees give it up completely. I agree that kakis in our kind of climate are less than perennial. Now that I know the routine I will be more quick to replace things.
I haven’t ever grafted onto D. Lotus because I’ve heard it is less suited to our heavy clay soils. Not sure if it’s also susceptible to the pathogen causing KSDS, but I doubt it would help save any D kaki grafted to it
I’m North of you in VA. I’m growing the D. Lotus trees from DWN and they are about same vigor as m111 in my heavy clay hillside soil. I also have a NG on DV but it’s few years younger in the same soil but I can’t tell a vigor difference between it and the DL+Kaki.
If both DL and Kaki are susceptible to the pathogen causing KSDS, it’s possible there’s a different reaction than DV+Kaki, assuming DV is resistent to the pathogen. Just extrapolating based on what @GrapeNut posted.
To my knowledge, I found no posts about DL+Kaki KSDS and knowing how prolific DWN trees are, it is a good sign.
I don’t know if it is the case or not, but it’s definitely possible Lotus rootstock trees wouldn’t have the same problem as DV+Kaki.