Gardeners, what is wrong with my pivet hedge? Pictures included.

Factual Questions
1

I have a beautiful pivet hedge, over 20 years old, that gets trimmed regularly. It has always been green from the foot to the top. Here is a total shot. About 10 months ago, bald spots started appearing at the base, like this.
Here is a detail shot.
The bald spots appear to be spreading. Does anyone know what causes it, and how I can restore the hedge?

My own theory was that it was caused by agressive cat pee. But that doesn’t really make much sense, because then the bald spots should also appear in the hedge at the back of my yard, yet that one is still green all over.

2

Any chance that it could be getting too dark at the base to provide for sufficient foliage. Proper hedge trimming techniues call for the shrubbery to be wider at the base than at the top to maximize the amount of light that reaches the lower portions. Does the hedge in the back receive more light?

On the other hand, the damage is just about as tall as a rabbit.

3

Would be one heck of a cat that could urinate to kill that much. That hedge is a beauty.

4

Spider mites = first thing that came to my mind.

5

I’m no expert, but I did stay at a Holiday Inn Express last night…

No wait, I mean I did watch an episode of “Ask This Old House” about hedge trimming. In fact, it’s online. Also on the site is a quick tip about hedges from the gardening guy, which is exactly what Kyboydal said about the “V” shape.

6

Kuboydal and ZipperJJ, I don’t think it is the shape. It has done well for twenty years in this shape, and the hedge gets plenty of light. It doesn’t get trimmed on the other side of the hedge, though, if that makes any difference.

The very local emergence of the bald spots makes me suspect that Philster is right, and some insect infestation may be the culprit. I have googled “spider mites” and " Privet hedge" for thirty minutes now, but I can’t seem to get any useful information from the net tonight. Philster, can you tell me more about why you thougth it was spider mite, or give me some link? Thanks muchly in advance.

7

Spider mites are wee little vermin most noticeable by their pointillated wounds on the underside that become visible on the leaf surfae\ce… and their webbing, which one can see when within a few inches of the leaf. You have what appears to be Ligustrum japonicum a good candidate for hedge-emitizing. Howzabout a nice closeup of the blank section? The loss of foliage is consistent with both shade and herbivorous predation. Application of a nice balanced fertilizer should spur growth, but the durn thing does look remarkably healthy.