Bacterial? Rapid infection on japanese maple

[Lars Grimm]

Hi All,

Another day, another problem. I love this hobby, but sometimes it can be very demoralizing. I have a very nice shohin japanese maple that very rapidly was struck by what I presume is a bacterial infection.

Day 1: The tree looks healthy. I decide to do some light clean up and remove some minor accessory growth. I pruned back a couple long shoots. Just very minor clean up. The scissors had been sterilized prior to use.
Day 2: Normal day, nothing special to the best of my knowledge.
Day 3: I go out to water my trees and notice that all of the foliage looks wilted. The leaves felt like they had lost all turgor and felt crispy. I assumed that somehow I had missed watering the day before. We have had temps in the 90s with high humidity. I felt stupid but put the tree in shade, watered it and assumed it was going to partially self-defoliate. Here is a picture from that day.

Day 4: My whole family gets a horrible GI bug. Enough said.... It rained though.
Day 5: The tree sits in shade. The leaves continue to look worse.
Day 6: I come home from work and have to move the trees around before leaving for a four day vacation. The leaves are looking pretty bad and so I decide to just defoliate them since they were going to fall off anyway. About 15 minutes before I have to get into the car and go, I notice a discoloration on one of the stems (see picture below). There is nothing I could do at the time, except fret about it while on my trip.


Day 10: I come back home from my trip and notice additional purple/black discoloration on many stems. It is very patchy, sometimes involving primary, secondary, or tertiary branches. See picture below.


I don't have a great zoomed out picture from before I left and I was in such a hurry I can't be sure how much/if this has progressed in the last few days. My assumption was that given the very fast rate of progression this must be a bacterial infection. I found this article from Michael Hagedorn suggesting it could be verticillium or pseudomonas. I just gave a total plant drench with phyton 27 and moved it to shade away from everything else. I have read that some people advocate pruning away infected areas, but some areas of blackening are where the primary branch meets the trunk. This would essentially require me to cut off almost all the primary branches.

Any help would be extremely appreciated!! I am at wit's end here as this seemed to come very fast out of the blue.

 

[coh]

Aw man, that's rough. I have never seen a tree go downhill that quickly. Hopefully someone with more experience in maple diseases will be able to offer some insight. I lost one a few years ago but it developed the spreading dark patches on the trunk before losing any leaves.

 

[River's Edge]

It looks like verticillium wilt based on the photos and description. It is a fungal disease based in the soil and basically untreatable. If it is, then the best treatment is to isolate and destroy to protect the rest of your plants.
The BEST way to check is to cut a section of an affected branch and look for dark areas ( brown ) in the rings or under the bark. The fungal infection travels up the vascular system and changes the color. Hope that is not the case but that would be my suggestion.

 

[AlainK]

Hope that is not the case

Unfortunately, it looks like that...

 

[rollwithak]

Super sad. Almost like losing a friend, depending on how long you’ve had it.

 

[0soyoung]

It looks like verticillium wilt based on the photos and description.

BUT, ...
Verticillium doesn't grow at temperatures above 75F.

Day 3: I go out to water my trees and notice that all of the foliage looks wilted. The leaves felt like they had lost all turgor and felt crispy. I assumed that somehow I had missed watering the day before. We have had temps in the 90s with high humidity.

Another possibility is that a day of not watering and in the sun, the root temperatures would skyrocket and could have been well above the ambient air temperature. Roots definitely are dying when their at temperatures above 115F/45C. Possibly the roots got toasted on day 2.

 

[Potawatomi13]

Hmmmm! Lost Vine Maple this Spring somewhat similarly only died back over a month at start of growth. Know was not high temps nor dryness. Much to think on.

 

[River's Edge]

BUT, ...
Verticillium doesn't grow at temperatures above 75F.



Another possibility is that a day of not watering and in the sun, the root temperatures would skyrocket and could have been well above the ambient air temperature. Roots definitely are dying when their at temperatures above 115F/45C. Possibly the roots got toasted on day 2.

A possibility for the toasty looking leaves, but would that account for the blackened areas?

@Osoyoung are you suggesting Verticillium would not be active when it cooled down at night or if the substrate was damp and did not reach those temperatures? After all i believe the other person was talking about ambient air temperatures not necessarily the temperatures in the pot throughout the the entire time or in every location. Such as in the shade or if frequent watering after the fact. Or during the time he was absent and the disease progressed after the plant was weakened.

Or perhaps you are suggesting that those temperatures would kill the fungal spores? I would be interested to know the specifics of the temperature range for activity and or eradication of the fungal spores.

I still think the best way to check it quickly is to check for discolouration of the xylem ring.

 

[Dav4]

I have no experience with V. wilt but I've lost maples to what I suspect is pseudomonas. The process took at least one month and was preceded by the typical slowly progressive blackening of the entire trunk... the leaves did not shrivel until the blackening was advanced and was involving 75% of the trunk (I applied phyton to no avail). For a tree to crash so quickly, the entire root system would have to collapse at the same time and I can't think of a pathogen that would move that quickly in a mature and otherwise healthy tree.

 

[namnhi]

Am sorry Lars but I afraid it is gone. The worst nightmare I have in the back of my mind when starting this hobby. I don't think you will really know the cause other than speculate.

 

[Cadillactaste]

Sickening...I lost my exposed root maple to similar looking black on branches. It went fast. My local nursery (which deals with treating disease and sick trees.) felt that the temps during shipment sent off the Domino effect that had been in the soil. In my case ...my stomach churns when I see you facing what looks the same fate. Sorry to see this .

 

[Lars Grimm]

Sigh, I fear the worst. I'm going to cut off one of the blackened branches and take some close up pictures. If it is lost, then at least I can share with the community.

I think I might just cut off everything that has any blackening and hope for the best. I have nothing to lose at this point.

 

[sorce]

Is it possible be it missed water on prune day?

The roots look black. Like they been dead.
Could be root rot..

Sometimes root rot kills off all the roots but the continuation of over watering keeps tree alive as a cutting. Until one missed watering.

Sounds/looks like that.

Sorce

 

[Lars Grimm]

Is it possible be it missed water on prune day?

The roots look black. Like they been dead.
Could be root rot..

Sometimes root rot kills off all the roots but the continuation of over watering keeps tree alive as a cutting. Until one missed watering.

Sounds/looks like that.

Sorce

It could have missed water on prune day. It wasn't intentional, but I was multitasking at the time.

I believe the roots look dark in that picture just from the water and shadow. I'll double check tonight, but I don't believe the surface visible roots are discolored.

 

[penumbra]

I agree with sorce on this one. I am sure it is root root judging the temperatures you are dealing with.
You know if you want to spend the money you can have it analyzed by a lab. Of course it will cost more than the price of a nice bonsai to do so. Alternately, if you have a local college that teaches horticulture, they might check it for free in their pathology lab. When I studied plant pathology we looked for good examples to evaluate. Just a thought.

 

[Lars Grimm]

I agree with sorce on this one. I am sure it is root root judging the temperatures you are dealing with.
You know if you want to spend the money you can have it analyzed by a lab. Of course it will cost more than the price of a nice bonsai to do so. Alternately, if you have a local college that teaches horticulture, they might check it for free in their pathology lab. When I studied plant pathology we looked for good examples to evaluate. Just a thought.

Is it worth trying to do an emergency repot?

 

[River's Edge]

Is it worth trying to do an emergency repot?

I tend to go in this direction if only to gain more information for the future. I have had plants wilt with crispy leaves and stubs turn black after pruning! What is different in your situation appears to be the blackening in areas other than stubs cut and the spread of blackening. This is consistent with research on Verticillum wilt. Also consistent is the timing, reports suggest that it often strikes after a period of cool damp weather and also hot dry periods. Essentially indicating that the pathogen is present and shows up rapidly when the plant is adversely affected. In this case you had the heat, plus pruning, plus a possible missed watering!
I hope the discolouration is not present internally on the vascular system.
The best case scenario would be some healthy roots and a recovery after repot. Just in case be careful with the soil and tools to ensure not spreading any fungal spores if possible.

 

[0soyoung]

are you suggesting Verticillium would not be active when it cooled down at night

Not unless it got below 75F at night. I don't know the conditions at 'North Carolina', but I don't think it gets this cool at night this time of the year in Charlotte.

So, a new verticillium infection, say from the pruners, would not be active. An existing infection would not be advancing.

The best case scenario would be some healthy roots and a recovery after repot. Just in case be careful with the soil and tools to ensure not spreading any fungal spores if possible.

Dip/drench the roots in 2 tablespoons 3% hydrogen peroxide in a quart of water. It will take care of bacteria as well.

 

[penumbra]

Is it worth trying to do an emergency repot?

Its your time so only you know if its worth it. My opinion is that this plant is dead and that the root system has been dead for awhile.

 

[rockm]

I ask this question whenever a tree goes south this quickly in warmer months--Do you own a cat? If so, does the cat like to hang around your trees? If so, consider cat pee being a problem. In a pot that small, a does of urine with the dissolved salts and relative acidity could be a big problem.