I’m worried about my Japanese Black Pine and would really appreciate some advice.
A few months ago, one branch lost all of its needles and now seems mostly dead. More recently, I repotted the tree because the roots already showed signs of root rot. Since the repotting, about 1–1.5 months ago, the tree has continued to decline. The needles are gradually turning yellow/brown, and I’m afraid I might lose it.
I also noticed some black spots on the needles and possibly a few fine spider-like threads, so I’m wondering if this could be a fungal issue, spider mites, or another pest problem. I’m not sure whether the current decline is mainly from the previous root rot, repotting stress, watering, or something else.
The tree is placed outside in a sunny spot with good sun exposure. The photos were taken in the evening, so they look a bit dark. I water carefully, usually no more than once per week, depending on the substrate moisture. I’m trying not to overwater, especially because of the previous root issues.
My questions are:
Does this look more like root stress/root rot, fungal disease, spider mites, or another pest?
Should I treat it with a fungicide or miticide, or would that add too much stress right now?
Should I remove the yellow/brown needles, or leave them alone?
Is there anything I should do immediately to improve its chances of survival?
Any advice would be greatly appreciated. I’m quite worried about the tree and want to avoid making things worse.
so I have done what you did with no success. root rot is a tough one. did you try a hydrogen peroxide drench at all to kill the root rot or just did a repot? tree is weak so pests are going to swarm it and take it down. If it were my tree I would leave it in its current soil and use high concentration hydrogen peroxide solution (10 to 20%) and treat two or three times as the hydrogen peroxide reacts with the top of the soil, etc. so gets pretty spent before it has the opportunity to kill the root rot organisms. then maybe some sort of spray on the needles to knock down the pests. I would give it less than a 25% chance of living. treat this as a learning experience so at least something positive comes from it. why did it get root rot in the first place? too much water? type of soil was not right? do a post mortem. sometimes the sheen still has organic rich soil at the base and causes distress in the tree. how much earlier repotting was done when the roots were healthier? it takes a few repots to get the sheen clean.
If I remember correctly you were having issues before repotting but of course it looks much worse today.
How did the roots look at repot?
Where there many healthy roots?
And now all of a sudden it seems sick or were the roots rotten or minimal at the repotting?
There is the Peter Chen moss trick
Which is to pull it out of the pot and soil.
Fill the bottom of the pot with long fiber spaghum moss, wire it into the pot
Back fill root system with more long fiber spaghum and then top it with a 1” or 2” of fresh bonsai soil.
Wash the old soil in hot water ( I know it was new but you are talking about root rot)
Dry it in the garage, shed etc and possibly reuse at a later date if the tree recovers
If the tree dies, throw out the soil.
This is NOT a Mirai technique and I am sure it is frowned upon.
The theory is that we air, layer in spag so we know it grows new roots.
I hate to see ya lose a nice tree, the advice you’ve gotten is solid. I would add spray with a fungicide and a mitacide to knock down any pest pressure and give the tree a fighting chance. The hydrogen peroxide dip will knock down the root rot bacteria, give it several treatments.
My last suggestion is something I’ve used to recover a black pine. I literally planted the tree in its pot into the ground to stabilize it. I left the tree in the ground for 2 seasons and it successfully recovered and regained its vigor. It might be a hail mary but I’ve seen mother earth do some miraculous things. Good luck.
