Just found a huge (white cotton-ey) mold problem in a container, unsure how to proceed!

[SU2]

As far as I can panic in the context of bonsais, this is the worst... I've got a 3.5 month-old bougainvillea yamadori that I put in a wooden box that's got very tall walls (an artifact of a sloppy transplant, it was my first large yamadori, a 1' wide stump) In a back-corner of that box, a spot where little light gets in due to the tree / foliage, I was checking to see how bad the trunk's dark-green mildew was - what I found was cob-web type (looks like incredibly loosely-spun cotton) pure white mold/mildew/fungus all over the media's surface and parts of the trunk in that area....

How do I approach this? Am unsure if I should be cutting-back everything in that corner and physically remove what I can of the white fluff, or if I should be re-potting with a fungicidal drench.... has also crossed my mind to sawzall the extra ~8" of box-height that's unnecessary but fear the vibration would be real bad for fragile bougie roots.. Any help would be greatly appreciated!!

[edit- I want to mention that my reasoning for thinking it's the too-tall box that's caused this is that I'd gotten a 2nd bougie yamadori, almost equally as large, about 2 weeks after this one, and it's got no issues - the only difference between the two is that the first one's got oversized walls, I imagine the lack of wind in there was direct cause!]

 

[just.wing.it]

Make sure its not just mychoriza....or however you spell that....
Got pics?

 

[twisted trees]

Make sure its not just mychoriza....or however you spell that....
Got pics?

Prolly not on a bougie. Sounds like mold.

 

[SU2]

Make sure its not just mychoriza....or however you spell that....
Got pics?

Unfortunately I don't, I quickly grabbed & threw-away all the substrate in that area but it was like 20" square of this https://i.stack.imgur.com/Yn00c.jpg It very well may be mycorrhizae(sp?) but I cannot imagine it's the type I want..

 

[SU2]

Prolly not on a bougie. Sounds like mold.

Why do you say not on a bougie? Bougies are the only specie I've learned of so far that does very commonly have mycorrhizae intermingling its fine roots in most cases (although this stuff, while it looks kind of similar, grew in a manner that's definitely not the good type intermingling the roots, I've got a ton of bougies and have never seen their myco growing far away from roots like this substrate-surface stuff, it looked like this https://i.stack.imgur.com/Yn00c.jpg )

 

[wireme]

Unfortunately I don't, I quickly grabbed & threw-away all the substrate in that area but it was like 20" square of this https://i.stack.imgur.com/Yn00c.jpg It very well may be mycorrhizae(sp?) but I cannot imagine it's the type I want..

Whatever it is its most likely harmless and I wouldn't recommend any fungicide treatment or anything. Possibly it will be contributing to decay of deadwood down there if there is deadwood. Cut the box down to get light in and it will not regrow I'll bet. A skill saw (circular saw) with the blade set low would create a lot less agitation to the box than a recip saw.

 

[twisted trees]

Why do you say not on a bougie? Bougies are the only specie I've learned of so far that does very commonly have mycorrhizae intermingling its fine roots in most cases (although this stuff, while it looks kind of similar, grew in a manner that's definitely not the good type intermingling the roots, I've got a ton of bougies and have never seen their myco growing far away from roots like this substrate-surface stuff, it looked like this https://i.stack.imgur.com/Yn00c.jpg )

 

[twisted trees]

Could be where I live. I've had bogies for twenty years and no mycho.

 

[twisted trees]

Messup...ignore or delete.

 

[SU2]

Whatever it is its most likely harmless and I wouldn't recommend any fungicide treatment or anything. Possibly it will be contributing to decay of deadwood down there if there is deadwood. Cut the box down to get light in and it will not regrow I'll bet. A skill saw (circular saw) with the blade set low would create a lot less agitation to the box than a recip saw.

Awesome thanks, will take my circular saw to it then! Was really hesitant to re-box as it's growing so well right now (as a 3mo old yamadori i'm doubting it's well-established in terms of roots!), will just use my circular saw to remove some of that height! I threw away all the bad substrate from the surface of that corner and defoliated/pruned the branches that were in there to allow light/air in, removing some height from the box should be enough!

Re "it will not regrow I'll bet" I'm inclined to agree, I was real worried about it when I found it last night but this morning was *very* relieved to find no new growth there, I'd been expecting it to just come back lol but it hadn't so hopefully it'll just be a memory after cutting the box!