Mushy bark on seiju elm--some questions

[justBonsai]

Hi,

Today I acquired from my local bonsai nursery a small seiju elm. The folliage is healthy and there are still new buds forming, it has a nice trunk and great nebari. Only costed me $29 and it was a great purchase in my opinion. That aside many trees from my local nursery tend to have small issues. Given the large quantity of trees that they care for many trees are not properly cared for with root bound trees, damp airless soil, and signs of bad health.

I inspected the tree very thoroughly and it looked healthy enough to purchase it. That aside there was some apparent rot on the trunk and surface roots. It appeared to be only on the bark as the bark was dark and mushy. I removed all the rotting portions, scrubbed it thoroughly with a toothbrush, and repotted the tree with pumice. By repot I mean removing as much surface soil and some bottom soil as I can without disturbing the root ball--given its a bit late for a full repot and 96 degrees Fahrenheit a full repot probably would of been too harsh. I covered the surrounding soil mass with sifted and washed pumice and gave it a thorough watering afterwards. Now the tree appears to be in great health and I hope the pumice can give it better aeration and drainage until next spring when I can remove the dense poor quality soil. That said can the rot/fungus re-emerge and cause further decay?

On another note, I scrapped the yellow-white surface you see in the pictures with my fingernail and it was a pale uniform color underneath. Is this a good thing? I though it would be green underneath or is this because that section is a root (directly above surface roots)?

(the exposed white/yellow areas were where I removed the rotting bark)

Thanks,
Julian

 

[justBonsai]

I have a slight concern. In the mushy rotted bark I had found very small white worms. Is there any insecticides I can use as a precaution?

 

[fredtruck]

To avoid mushy bark on this elm, and others with lots of cork, you need to water in such a way that the trunk does not get wet. You can do this with a small watering can or you can do it with an automatic irrigation system using misters--that's how I do it. Whatever works.

 

[Zach Smith]

I have a slight concern. In the mushy rotted bark I had found very small white worms. Is there any insecticides I can use as a precaution?

The white worms are most likely bark beetle larvae. Most commercial insecticides will kill them. I think you'll need to spray the entire tree, as the life cycle begins elsewhere. Google elm bark beetle and you should find what you need to know.

Zach

 

[mcpesq817]

Be careful with the mushy bark. I can't see the pictures for some reason, but the mushy bark can lead to rotting and insect damage.

I bought a big seiju from Brent a few years ago. I happened to notice a couple of pill bugs on the trunk, and started scraping out the mushy bark. By the time I was done cleaning out all the bark and punky wood underneath, I ended up with a pretty substantial hollow in the center of my trunk. I don't know if the pill bugs caused it per se as maybe it had been rotting out and the bugs decided to set up shop there with the rotting environment, but either way, the presence of certain bugs can indicate a rot problem. Two weekends ago I was cleaning the seiju out and found that ants had set up what looked like a little nursery further up in the hollow (it looked like they were running off with the larvae when I was picking at the section that seemed a little punky). Another very annoying discovery. I've also seen those tiny white worms in the past as well.

Originally I was disappointed in all the damage, especially after what I had paid for the tree. In the end though, the damage done added a lot of character to the trunk to the point that it now has the potential of being one of my best trees.

Watching your watering habits helps, but at the same time, if you have rain every day like we have had here, the trunk is going to get wet and stay wet for extended periods. One thing I've found is that if a number of sacrifices were grown to increase the caliper, what ends up happening is that there will be a layer of the cork bark in between the woody sections of the branches. Even if you chop those branches off, you're still left with that bark on the inside. Because that bark is less exposed, I think it retains moisture a lot longer than the normal cork bark on the outside of the tree - that leads to rots, bugs, etc. My seiju had a number of big knobs at the base indicating that Brent grew out a lot of low sacrifices to get that trunk base caliper. That technique clearly worked, but I think it also led to an easy pathway for rot and bugs to make their way to the center of the tree.

 

[M. Frary]

Since I use Diatomaceous Earth I have no bugs in the soil. Ever. It gets in the cracks of the exoskeleton and irritates the heck out of bugs. If it wasn't gray in color I would recommend it as just a top layer maybe.

 

[justBonsai]

Thanks for the replies. I treated cleaned up the area and visually it still looks fine. Most of the bark is still there and there's some exposed dead wood that adds nice character. I treated the exposed dead wood with some tea mixed with lime sulphur to maintain a brown color and to preserve the wood as well. I can't help getting the trunk wet sometimes but its exposed to the air and the top layer has pummice so it dries pretty fast.

 

[M. Frary]

I had one for a few years before it succumbed to last winter. I never had an issue with the bark ever. I drenched it and all of my trees every day. The bark was always nice and and hard when I scrubbed it with my wife's toothbrush every month or so to get the moss off.