Hello

Yes, the tree should have been watered when the weather was dry for more 10-14 days and hot, say above 85F. 

Yes, the dry dead leaves are most likely the result of not receiving enough water. The other possibility is some issue with roots such as rot, or verticillium wilt. 

You did a scratch test, and found that the twig was moist and green underneath- this is a good sign. These twigs should leaf back out next spring. 

Do not prune anything yet. Wait until early next summer and prune dead ones then. Keep the tree watered from now until the ground freezes. Check by going under the mulch and going down 6-8 inches or so. Soil should be damp but not sopping wet and sticky. Water the tree with a slow soaker hose, or a sprinkler set on a trickle, all the way around the root zone, moving the sprinkler around he tree. After you think it has had enough, perhaps after 1-2 hours, check that soil is moist down 6 inches or more. If you have clay soil be very careful not to get too much water down- no puddling or running off. Clay usually needs rain or the hose  much less than Sandy soil. Keep mulch nomdeeper than 3inches and mulch should not touch the trunk. If we get good, long soaking rain you count that as a watering, too.

When the ground gets cold and starts to freeze put the hose away, you are done until next spring. 

Even though the tree has dropped its leaves, it is not necessarily dead. Therefore keeping the roots watered, with out drowning it, is your best bet. Spring will tell you what is alive and what isn’t. There could be some die back. 

For your reference—

To find a certified arborist to assess the whole tree for disease, pests and growing conditions search by zip code here—- www.treesaregood.org

Info on verticillium wilt, something to watch for—-

http://msue.anr.msu.edu/news/verticillium_wilt_refresher

Let me know if I can help again. Pictures of the whole tree, the base of the tree, and clear close up of leaves in question will help us in future. Thanks for using our service.

You are very welcome. This is a real beauty of a tree. Rather than depend on me looking at a picture, and maybe being wrong, I would do one of two things:

I would send these pictures, leaf samples, both partly dried up ones and some healthy ones, and at least one branch sample with the problem leaves attached to MSU Plant Diagnostic lab. They will examine them under a microscope and can tell if  there is insect damage, fungus, or leaf scorch. The branch  is how they can check for verticillium wilt. Their fee schedule( I think the fee is about $25), form, and instructions  are here—-

https://pestid.msu.edu

The second thing would be to hire a certified arborist to come on site and examine everything. This costs a little more but is minor compared to the value of this specimen.( I think it is about $70-$100) That is the website mentioned earlier—-

Www.treesaregood.org

I do suspect leaf scorch. We have had one of the hottest summers. Consider if anything else in the area has changed— has a shrub or tree that used to shade this plant part of the day been removed or pruned back? Has the root zone been disturbed by planting something near by or other digging? Chemicals applied nearby to lawns or other plants can volatilize in summer heat and drift over to sensitive leaves. As you can see, a close examination of the leaves and stems is in order. I hope this tree comes back for you!

I want to give you an update on my Lace leaf (dissectum) Japanese maple.  Bordines sells the Tamukeyama and the features it lists suggest it could be my variety.

I sent my same photos of the tree to my sister.  She worked at Bordines in Rochester Hills for years.  She also said that it looked like LEAF SCORCH and said I should be watering it to help it get through this dry period.

Yesterday I went out and got close up to my tree’s canopy.  I gently removed all the dead leaves with my finger tips.

What I found underneath the worst blobs of dead leaves are an inner layer of LIVE green/gold leaves still getting water from many of the same branches.

The LIVE leaves were spared because the outer layer absorbed the hot sun’s damage.

I am going to leave the tree [without any pruning] until next year and see what the next crop of foliage looks like.  I will have some die back, but it may be limited to the south side that cannot be seen from the street.

I plan to water it regularly until leaf drop this autumn.  In early October [in a non-stressed year] the foliage would turn dark red/maroon and last for several weeks.

I believe my maple will survive without too much permanent damage.