Hello Patricia, and thank you for contacting the UVM Extension Master Gardener Program with your question.
Thank you for including the photos - that helps greatly in understanding what might be going on!

I am sorry to hear that you are having issues with your apple trees.

I have two questions for you:
1) are these recently transplanted trees?
2) are there any signs of insects either inside or underneath the curled leaves?

I'll watch for your response and share more material soon.

Thank you,
Michelle

Hello Patricia, and thank you again for contacting us at the UVM Extension Gardener program with your question.

As I mentioned earlier, our responses might depend on some other circumstances not yet evident, though I'm going to provide you with some resources to help you understand what could be going on.

One possibility is transplant stress, which would depend on how recently you put in these tress (they look quite young) and how the planting site was chosen and set up.  It could be that they are responding to their new surroundings and will settle in for future fruiting years with extra care to keep them watered - but not drowning - during this very hot summer.  

Another possibility is either powdery mildew or an insect infestation.

The articles below will help provide some more information for you, both in diagnosing and treating the trees to help keep them healthy.

Different causes of apple leaf curl, from Univ. of Minnesota
https://apps.extension.umn.edu/garden/diagnose/plant/fruit/apple/leavesrolled.html

Transplant shock or infestation?, from Univ. of Maine
https://extension.umaine.edu/gardening/2021/02/22/curling-leaves/

Please let us know if you still have questions, Patricia.

I wish you success with your fruit trees,
Michelle