Bonsai Soil leaving elms generally more open to disease

[sono_ben]

Hello,

So I have about 11 pre-bonsai about half of them I up-potted into larger nursery pots with generic potting soil mix so that I could grow them more. The other half I potted in grow boxes with typical bonsai soil (Akadama, Montmorillonite Clay (because I could not afford straight akadama so I cut it), Pumice, Lava). Over all growth has been great this year and I had much brighter greener leaves in the grow boxes with the bonsai soil then those in the potting mix so I was loving it especially early spring. However as the wet part of spring rolled on all of the plants in the bonsai soil had issues with fungal diseases (mainly black spot) and none of the trees in the potting soil had any issues.

I wonder if this jives with anyone else's experience. Is the issue that the soil was too sterile so when the baddies moved in there was no good stuff to compete? Are there any changes I should make next year to ensure I do not deal as much with fungal issues especially as I am planning on moving more trees into grow boxes with a similar mix?

Any help in understanding this would be greatly appreciated.

 

[Srt8madness]

Are they all side by side? Are the trees in organic soil in a different part of your yard?

Did you bare root and wash them when you planted in bonsai soil? If not then the "sterile soil" theory wouldn't really apply.

I can't give you an answer but those are some bits of info that could help.

 

[sono_ben]

Are they all side by side? Are the trees in organic soil in a different part of your yard?

Did you bare root and wash them when you planted in bonsai soil? If not then the "sterile soil" theory wouldn't really apply.

I can't give you an answer but those are some bits of info that could help.

They were all side by side until some got infected with fungus - those got isolated until I could treat for it.

I did bare root them but I did not wash them (that is a good point)

Thanks for responding - I am a bit flabbergasted by this but want to make sure I give my trees the best chance going forward.

 

[rockm]

Black spot really has nothing to do with the soil. It has to do with too much water on the leaves and the proximity of an infected tree to others. It's an "above ground" infection. It is present on leaves and twigs, particularly dead leaves and twigs. It may seem like there's a clear delineation of what got it and what didn't, but it's probably not that straightforward and obvious. The disease is already present on leaves. It appears in overly wet weather. The infected trees are likely just farther along with the infection than the others. It's not that a big of a deal for most medium to larger trees. My cedar elms get it when it's very rainy. Leaves look awful, but the trees shake it off.

 

[Tieball]

I found black spot I had was caused by too much water and not nearly enough air circulation and sun exposure. I then used a fungicide and improved the area around the trees for better air movement and longer sun times.

Whether right or wrong, I removed any black spot damaged leaves and any leaves around the tree as part of the treatment. The trees responded very well but it took nearly the entire season to completely fix the situation. It worked for me.

 

[sono_ben]

Black spot really has nothing to do with the soil. It has to do with too much water on the leaves and the proximity of an infected tree to others. It's an "above ground" infection. It is present on leaves and twigs, particularly dead leaves and twigs. It may seem like there's a clear delineation of what got it and what didn't, but it's probably not that straightforward and obvious. The disease is already present on leaves. It appears in overly wet weather. The infected trees are likely just farther along with the infection than the others. It's not that a big of a deal for most medium to larger trees. My cedar elms get it when it's very rainy. Leaves look awful, but the trees shake it off.

Yeah - we had a lot of rain this spring! Not much I was able to do to keep the trees drier.

 

[sono_ben]

I found black spot I had was caused by too much water and not nearly enough air circulation and sun exposure. I then used a fungicide and improved the area around the trees for better air movement and longer sun times.

Whether right or wrong, I removed any black spot damaged leaves and any leaves around the tree as part of the treatment. The trees responded very well but it took nearly the entire season to completely fix the situation. It worked for me.

Yeah I think I have eliminated the issue this year now that we are finally getting some drier weather but I just wanted to see if there was something else I should change next year