Weak yellowing candles on JBP

Hi everyone…Been doing some late pruning and trimming on my jbp just before our soft winter here in Sydney Australia…Now it s the end of spring…All of my JBP responded well so far…but noticed that one of them started to slow down once the back budding took place…some buds turning weak and yellow to dry out in worse cases…even the strongest shots and candles are weaker and weaker…The new needles are light green and also shorter atm…The alarming sign was the yellow brown coloration and weak growth…can also notice droplet of sap at the base of some of the weak buds and candles too…?

So i stopped the watering to let the soil dry out well in case of root rotting…
Really don’t know if need to treat for underground bugs etc…?
Don t know if I should change the soil as an emergency procedure as the tree is already weak like that?
This pine has been repotted 2 years ago and it s my good mate!

Based on your description and the weak growth evident, i would repot. This is an acceptable time in your neck of the woods. Check carefully for pests and compaction. Remove all dead or decaying roots that you might find and cut back to live. Try to do this slowly and keep as many healthy roots as possible. If available use a free draining mix with similar particle size. It is best if the particles are irregular in shape rather than flat surfaces.
Best of luck

Because it’s a bit late for repotting (that’s my guess based on the new shoots), take care to preserve as much as the rootball as possible. This may seem at odds with the idea of exploring and removing compacted pockets of soil, but the idea is to preserve as much rootmass as possible where the soil is good. I’d also expect the tree to need frequent misting after repotting and some protection from strong sunlight.

So repotting is a must for this case?
Root rotting?

I would not say it is a " must" . Rather checking the soil compaction and root condition is a preferred step at this time.
based on the pictures and description checking the roots and soil condition should provide valuable information.
If their is root rot, it can be corrected, if there is soil or pest issues they can be identified and addressed.
This is a better time for an emergency repot then several months from now if the tree continues to weaken.
The aftercare is very important as Jonas has indicated.

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Ok , that s vey clear, i decided repotting with new drainy soil…
what are the most important points for the aftercare?
Semi shade, misting, how about the watering frequency etc?

The specific aftercare should be tailored to your regional climate! As a pine it is best to allow the soil to dry out a bit before watering. However the roots should not dry out, the soil should retain some moisture. Sunlight aids the photosynthesis that fuels root recovery. Avoid extreme heat and very drying winds if common in your area this time of year now that spring is over! Being in Sydney, Australia that is a long ways from the Pacific Northwest and Vancouver Island. If possible get some help from an experienced Bonsai person in the local area for specific aftercare.
If you are switching soil types then be very careful to check moisture levels in the pot regularily until you are familiar with how fast the pot dries out and how much moisture the tree requires. Compacted soil is very different from free draining soil in water retention and frequency of watering required.
Best of luck!

Thank you for the precious info! Jonas was advising frequent misting…Does my new transplanted pine will need constant misting or what will be the frequency?
Can i use product like Superthrive in my water for the pine to help recovery and trigger root growth?

I think the misting will be beneficial if the humidity is low due to temperature or windy conditions. I have not used superthrive for over a decade once i became aware of the research being inconclusive as to its effectiveness. The additional cost did not seem warranted at that point.
Some people in Bonsai still believe and love the product. I don’t think it will create a problem if you decide to use the product.
I am a firm believer in attention to detail in the repotting process, watering routine and aftercare moreso than supplements! Other than fertilizer at appropriate times i do not use any supplements. The exception is rooting hormone for cuttings and airlayers!
I am sure there are many different approaches throughout the industry!

I’m with Frank - careful repotting and proper aftercare (limited sunlight, misting when necessary) will be the most important thing for the tree.

I have yet to use supplements so I can’t recommend them based on experience and there’s no good evidence they do anything.