What is wrong with nt Lilac?

This is an old Lilac bush--but, overall, it is growing well and its blooming
has improved from the last couple of years since I have been pruning out some of the
really old, yukky, stems and the new ones seem to be growing OK.

This bush has been growing in this site for ages. My neighbors did put up a 6' fence
all along their property about 5 years ago.
Much of the Lilac bush that faces the fence gets no sun at all. Air circulation is also poor
back there. I will show you a picture of the whole bush and how it is located in the next post.

Right now--a good part of this bush has these leaf issues that emanate from
one particular stem. Not an old stem either. It is in the center of the shrub.

Many of these leaves are turning black on many of these branches. Even high up.

Anyone have any ideas? Suggestions?

Thanks, Gita

Pictures 1-2 and 3 shows various shots of the sick leaves

Pics. 4 &5 showa the healthy parts of the same bush. These branches face the garden.

Here are looking at the whole bush, and how it is located, from 3 different angles.

Pic, #3 is taken from the garden side. It gets a bit more light there--
but not much--as you can see it is pretty much under the canopy of the big maple tree--
as is most of my back yard.

I am not an expert on this--but I do think it is not a "disease" per say.
It seems to be more of a situational issue.

Thanks again. Look forward to your ideas.

Gita

Could the neighbor be applying something to the soil that is affecting the lilac? Browned edges are often a sign of salt or lack of water. Salt is not just sodium chloride, but can be fertilizer, or any of a long list of things.
Related (though 5 years is a long time) could concrete from the post holes be making the soil alkaline?

How about herbacide? I also see sort of blotchy yellow and green leaves.

Suggestion: Run a garden hose near the fence, perhaps move it a couple of times, to deep soak the plant, and flush out the root zone. If you need to, build a berm along the fence to keep the water from just running off. Make sure it goes down into the soil. Do this perhaps twice a month for 2-3 times. It will be difficult to assess the success of this so late in the season. The plant will probably not put out much more in the way of new leaves before it goes dormant.

Thanks, Diana...
Of all the things you suggested, the lack of watering the bush is the only thing
that I am guilty of.
There are 2 Hostas growing under this bush (see pic. #1 above) and I do water them
every time i water the beds.
You can also see a bird bath (in pic. #3) and I dump that out right under the Lilac
when i change the water.

My neighbor behind the fence is from Pakistan. I do not believe she applies anything to the soil
near the fence. What grows on her side along the fence are mostly DL's and other plants that.require NO attention. She pretty much gardens in pots.

When the fence was put up--I do not remember them using any cement.
They just dug holes. That fence made me so mad--I did not talk to her for 2 weeks...
Her daughter told me that "That is how they garden in pakistan"--behind high fences.

SO--other than the watering--I cannot come up with any other reason.
Something systemic????

Gita

Give the lilac some deep, thorough soaking. The amount of water from a birdbath almost does not count (unless the birds have a super deluxe birdbath!)

The daughter is right about gardening in that part of the world.
Gardening originated in that area, and one of the first features built was a wall.
Outside the wall: Desert. Raiders.
Inside the wall: Water flowed under control, in fountains. Plants were grown mostly in raised beds or containers. They were fragrant, edible, lush growth. All these things helped to make the distinction between the wild, inhospitable desert and the pleasant, safe haven of house and garden.
Whether this method of growing things needs to be continued in a moister climate with generally pretty decent soil is a question for another thread.

Diana--Thanks. I will put the hose there on a slow trickle.

maybe i should use my soaker Hose? Why have one if I never use it?

Gita

This is a perfect use for one. The goal is to use the soaker hose to allow the water to seep in slowly to the soil without running off. This will flush out fertilizer and salts out of the root zone, and give the plant more water.

I KNOW...I KNOW....been at all this for Eons.

It is really inconvenient to connect the hose from the outside faucet and then
pull the soaker hose across my patio and lawn until it gets to where the Lilac is.

I suppose I can live and do this a few times a month. I will survive!

Gita

I know, I am probably repeating something that experienced gardeners already know, but people new to gardening may also be reading this, and a bit of explaining can help them understand why and how to do something that we already know about.