AusBonsai

Hey all - Im growing this 'Royal Frost' Birch, and currently trying to air-layer the top two sections. It's taking it's sweet time, but while I've been waiting i've noticed that it has curled most of the leaves to a large degree. Is this simply heat/humidity stress? It is in a pot and I dont believe my watering routine is too far off the mark.
I dont believe there are any pests (that are visible at least) - I discovered a few spiders who had taken nest but that's no problem (I assume). Any thoughts? Is this even a problem to worry about? TIA.

is it only the leaves on the air layers or all of the tree

Whole tree!

check under the leaves for bugs-- if possible remove from pot to check moisture level and root health-replace -if not too soggy I would immerse it in a bucket until it stops bubbling -remove and observe how quickly it drains. Not sure if we have birch borers in aust

It's a tall tree, but I should be able to remove it from the pot to do that. Thanks for the advice!

So, definitely no bugs on the leaves!
It has been raining today. The top did look like it had dried somewhat despite the rain today, so I had topped it after work today with a quick spray, so I dont believe the soil is too waterlogged based on the water it's had today. Here is a shot of the roots - they seem to look ok to my green eyes.

Birch are naturally stream side trees and are normally very thirsty. To my eye those leaves look dehydrated. It may have only been 1 hotter than usual day to cause this.
Roots look fine and plenty of water there now so that it recovers.