What's happening with this JWP?

[NashsMan]

I bought this JWP "Azuma goyo" in May 2024 and then waited for the right season to do a half root repot in February. Potted it in 70% pumice, 30% coco coir which has worked well for my JBP and JRP.
It's been doing well and putting on lots of new healthy growth since then.
But this past week we've had very hot temperatures (upper 90's) as a well as drenching rain storms.
I have sheltered it frrom repeated soaking by putting it in my greenhouse, but I still think it's had more rain than JWPs would like.
Is this a fungus? What to do?

 

[River's Edge]

I bought this JWP "Azuma goyo" in May 2024 and then waited for the right season to do a half root repot in February. Potted it in 70% pumice, 30% coco coir which has worked well for my JBP and JRP.
It's been doing well and putting on lots of new healthy growth since then.
But this past week we've had very hot temperatures (upper 90's) as a well as drenching rain storms.
I have sheltered it frrom repeated soaking by putting it in my greenhouse, but I still think it's had more rain than JWPs would like.
Is this a fungus? What to do?

It appears to have affected the new apical shoot tips on most of the stronger branches. I would suspect the heat and drying out. The heavy rains rarely build too much moisture in the mix you describe and a colander.
Another option might be pine shoot moth, however I would not expect it to affect the plant in so many locations at once. When you cut off the affected parts if there are no holes or sap at the base of the dead portion it is not pine shoot moth.
I would not suspect a fungal attack.
At this point I would cut off the affected parts, seal the cuts and observe. Your mix is one that can dry out quickly and white pines like more reliable moisture levels than JBP and JRP. They are also a pine that prefers cooler range of temperature so the higher heat would have contributed.

 

[Shibui]

Agree. Growing tips are most susceptible to dehydration. The new soil mix is way more open than you are accustomed to, the colander dries out way more than a traditional pot and it's a big tree in a small pot so it's likely you're not keeping up with water.
Which half did you bare root? Looks like all new soil in the photo.
One of the down sides to different media in a pot is that water doesn't cross from one to the other easily. The roots can be taking water from the inner (old) part but water just runs through the new (outer) soil without wetting the older, inner soil = dehydration. I have occasionally had the opposite happen where the inner soil stays too wet because excess water cannot move out into the new, more open mix.
I note the chopstick moisture meter. Guessing it is in the older soil? What is it telling you you about soil moisture?

 

[NashsMan]

Agree. Growing tips are most susceptible to dehydration. The new soil mix is way more open than you are accustomed to, the colander dries out way more than a traditional pot and it's a big tree in a small pot so it's likely you're not keeping up with water.
Which half did you bare root? Looks like all new soil in the photo.
One of the down sides to different media in a pot is that water doesn't cross from one to the other easily. The roots can be taking water from the inner (old) part but water just runs through the new (outer) soil without wetting the older, inner soil = dehydration. I have occasionally had the opposite happen where the inner soil stays too wet because excess water cannot move out into the new, more open mix.
I note the chopstick moisture meter. Guessing it is in the older soil? What is it telling you you about soil moisture?

The chopstick is in the more open, new soil. So in the first photo with the whole tree, the new soil is on (approximately) the right; old soil to the left.
I did top dress the old soil on the left.

When I cut off the browning tips yesterday, there weren't any holes so there don't appear to be any moths.

Interesting that a different JWP, different variety bought at the same, but planted in a wood grow box in the same HBR soil mix and growing side-by-side with the 'Azuma goyo ' is showing no signs of stress.

I've always read and been told by mentors that JWP "are happiest when they have to search for moisture ". Like my several JBP and JRP (all in the same soil, but also all in 100% open soil mix), they all get watered only when dry. The only difference with the 2 JWP is that they are growing closer to the greenhouse so they can be quickly sheltered from too much rain.

 

[Leo in N E Illinois]

How hot did it get in the greenhouse? Upper 90's outside can easily soar to 110+F in the greenhouse. Is it possible that while sheltering out of rain, in the greenhouse it got "cooked"? New growth would show heat stress before older growth. I'm just asking, not "telling".

'Azuma' is my favorite cultivar of JWP, and in my experience it is a little more sensitive to less than perfect cultivation conditions than seedling JWP.

 

[NashsMan]

How hot did it get in the greenhouse? Upper 90's outside can easily soar to 110+F in the greenhouse. Is it possible that while sheltering out of rain, in the greenhouse it got "cooked"? New growth would show heat stress before older growth. I'm just asking, not "telling".

'Azuma' is my favorite cultivar of JWP, and in my experience it is a little more sensitive to less than perfect cultivation conditions than seedling JWP.

It's a good question and the greenhouse does get over 100° F. when it's sunny. But I'm retired, so the pines are only in there when it's raining. As soon as the sun comes out they get moved outdoors.

 

[Shibui]

The chopstick is in the more open, new soil. So in the first photo with the whole tree, the new soil is on (approximately) the right; old soil to the left.
I did top dress the old soil on the left.

I would put another chopstick into the older soil to double check how it is retaining moisture. It may be much drier or much wetter than the new soil even though it's all in the same pot.