Blackspot on Elms...

[Wm Tom Davis]

With the new leaf growth coming, one of my Yatsubusa Elms is showing signs of the fungal problem of Blackspot. I've begun a regime of total spraying of both sides of the new foliage every 3rd day for three weeks now and the problem continues, albeit not as much. I've quarantined it in a separate area so that my other elms won't get infected.
I'm using Bayer's Advanced Disease Control in a sprayer for now and am wondering if there is any systemic fungicide that will work to combat this fungus? It is my understanding that it comes about when watering by spraying. To use a sprayer to apply a cure seems a bit odd to me.

Any help or suggestions would greatly be appreciated, as I have done a search on this and other bonsai websites with very limited results.
I look forward to your comments and help.

Thanks, ~ Tom

 

[Gnome]

Tom,

I've had to deal with this problem every year since I began with Chinese Elms. It's important to know that any treatment will not cure any leaves currently affected. Furthermore those leaves must be removed in order to avoid spreading the disease further. As you mentioned, don't water from above. I have even gone so far as to shelter mine from rain during the spring. It seems the new, tender leaves are more susceptible than leaves that are older and hardened off a bit.

For treatment I have used Daconil with good results, but again in conjunction with removal of infected leaves. This year, in an effort to go green, I intend to try Neem Oil as a natural fungicide. I think someone on this board did mention a systemic but I don't recall the name. If you search you should be able to find it.

Norm

 

[mcpesq817]

I've had a rough time with black spot on my regular chinese elms (spraying didn't seem very effective), but cork bark varieties seem immune to it. So, I've stuck with cork barks.

 

[ml_work]

Tom,
I've had to deal with this with my Chinese Elm too. Someone had told me about "Orthenex" to stop the Black Spot. I had a hard time finding it, got some by Ortho that I mix with water. As Norm said it will not cure the existing leaves but it did seem to help so it down. Could have been Norm that told me about the water causing it and when we had days of rain in a row is when I would see it come back. I started watering just the soil and not the entire tree, if we did not have rain for a week, then I would water from above 1 day. Also any leaves that fall into the pot should be removed to keep it out of the area.
I was just about to move mine from under the carport but saw we were getting rain the next 2 day. Now I will wait to move them and just as Norm said I think I will shelter them when we get days of rain.

Keep LOOin Up!
Michael

 

[DaveV]

The systemic that I referred to is called INFUSE. I get it at Earl May and it does a great job and does not harm my elms. I have used it during an infection and now more often as prevention.

Dave V.

 

[rockm]

Your elms are leafed out in Zone 5 Chicago? My elms here in Zone 7 don't have any leaves yet and they're only just beginning to emerge.

The location of yours (indoors?) most likely is playing a very large roll in the problem. Black spot can crop up when things are kept too wet- especially the foliage. Watering foliage (without antifungal additive treatments) spreads and perpetuates the problem.

FWIW, damaged leaves do not "heal." Once a leaf is damaged, that damage will not go away. Trees simply shed the worst of them.

 

[Wm Tom Davis]

Thanks Norm for your informative reply. Everyday with tweezers I pick off infected leaves so as to try and keep them from infecting the soil.

mcpesq817, I too have corkbark elms with older & thicker leaves. I agree that it is much hardier in its resistance to blackspot.

Michael, I've had good success with Orthonex with my roses. I haven't tried it on my bonsai yet. Again I'm looking for something systemic, and not topical.

Dave, thanks for the suggest on Infuse. I checked into it and it comes in different application forms, and had some good comments from other users... Thanks.

Rockm, Yes I am an indoor bonsaist. I also give certain trees their dormancy periods in our cold basement for three months, which I started doing this past November. In February I brought them out of "hybernation" and began to give them increased periods of light and warmth. I also keep a large humidity tray underneith my light bench. A picture of it can be seen on Jerry Meislik's website,
http://www.bonsaihunk.us/info/GrowingStand.html
I have had very good results with it so far, and it didn't cost me an arm and a leg.

 

[rockm]

No need to be defensive. All I was saying is the conditions for your trees could be too wet and could be a big contributor to your black spot problem.

It may not even be lack spot-as this disease typically arrives in summer when humidity is high and temperatures are too. It might be that you're simply overwatering (a common thing with indoor bonsai) Overwatered trees develop yellowed, blackened and crispy leaves that fall prematurely.

Black spot, in itself, isn't really that big a problem, as it usually passes as autumn arrives. I've had it a couple of times on collected elms outside. They recovered quite well after I began monitoring their watering more closely...

 

[Wm Tom Davis]

Interesting read Rockm... There is no need for me or anyone to be defensive. I was stating your keen observation regarding the leaves that have already begun to bud and grow as to where I am living in Chicago. As an indoor bonsaist, I'm quite happy with how my collection is progressing, and enjoy the sharing that takes place here.

Thanks for your experiences about watering, but that is not the problem. As with you, blackspot seems to be a continual problem with me as well, and seeings how I'm continually learning, I'm always trying to find new ways to keep my bonsai healthy. I like to hear & read about new ways to do so, hence I ask questions.
I do appreciate your comments.

 

[rockm]

"watering, but that is not the problem...blackspot seems to be a continual problem "

I've not had a continual blackspot problem in my 15 years of keeping a variety of elm species. The fungus has come and gone a couple of times and I've found it was due primarily to factors involving watering. tighter control of watering, stopping overhead watering of foliage (and not misting), placing the tree in a place that gets more air circulation--which dries soil and dew out quickly, can all help.

Since the fungus involved thrives in wetter conditions,

http://www.extension.umn.edu/distribution/horticulture/dg0766.html

your problem is most likely related to water in some way, either from too much humidity, overhead watering, too much watering of the soil, soil that doesn't drain properly or a combination of all of these.

 

[Wm Tom Davis]

Thank you rockm for the clarifications.