Dawyck golden beech leaf rim margin turning yellow

(Question)

Hello. I just spoke.with one of your master gardeners(ellen/very pleasant) and she suggested i post some pics. I have 9 golden beech in the back yard close.to the fence. They are 4 years old and have been growing well. I water for.about 1min per tree about 3 times per week. This year 3.of the trees appear to have been turning yellow/brown around the leaf rim. Mostly the bottom.half of the tree. Not.sure.whats going on. The trees.in the backyard are easterly direction so by 4:30 get no.more sun.

(Answer)

Thanks for your kind words about our volunteer!

Now, the first image you provided seemed to match Acalitus Stenaspis mite damage, but that is a pest in Europe primarily.  However, the additional pictures you provided appear to show dark stripes forming on the leaves, which might indicate BLD, that is, Beech Leaf Disease. It is a serious disease, also caused by a leaf-eating, microscopic worm-like nematode, Litylenchus crenatae ssp. Mcannia. Please review this BLD information:

Please also note the BLD “look-a-likes” described on this fact sheet on beech problems:
A Woolly Aphid infestation, for example does not endanger the trees, as would BLD. However, you would be seeing fuzzy white material on the leaves in that case. And they would be very sticky.
In any case, I recommend contacting a certified arborist. You can find one here on the International Society of Arboriculture’s searchable database.