Well, I don't know about expert at Privet problems in The Lone Star State, but I can abide a little Friendship in helping sort out a problem.
I will thank our friend
Stack24 for posting a lot of good pictures and closeups - without having to be asked more than once! Subsequently, chasing down a lot of leads online is additional going above/beyond. How do you say "Kudos" in Texan?
I will ask
Stack24 (and others here) that when you look up and find online stuff, go ahead and post that link with your commentary about it. It saves others lots of time if they wish to review it, and assist you in finding a solution. You could still go back and edit your previous posts, inserting these links - or post it in a followup here referencing what you found or didn't find useful.
I would also ask
Stack24 to identify which species of Privet (
Ligustrum sp.) that these are, since you can grow a lot of different ones in Houston. It may not matter to this particular pest, but it could help eliminate some of the possibilities. Since you know the person that grew them, this shouldn't be hard to nail down.
The previous posts are hitting on a lot of the insults that afflict landscape plants. Those are all good issues to review, research, inspect, and/or rule out if they don't apply this time. One of the best - and which should always be asked - is the quality of the plant at procurement and the method of installation. One might identify a pest, kill/resolve that problem, and go on to continue to have poor plant performance because of the inherently cultural problem of underground circling roots or buried basal flare. Similarly, eliminate off-site sources of problems - like neighbors spraying/applying things, excessive runoff from elsewhere, or handyman dumping cleaners/chemicals in the landscape bed.
The congregation/eruption of all those buds (little nodules) at the leaf nodes are - to me - indication of witches' brooming (many growing points very close together) but without stem growth or leaves. That points me squarely toward suspicion of a Mite Infestation. Mites (little arachnid b@st@rds) do their nefarious thing almost completely hidden - because they are mites, tiny, going generally unseen.
Here are some links I found:
https://content.ces.ncsu.edu/p...
https://content.ces.ncsu.edu/p...
A category of these devils called Eriophyid Mites can cause Witches' Brooms. Anyone who gardens where Hackberry (
Celtis spp.) grows knows exactly what this term means - I'm e-looking directly at
porkpal - except what is obvious with Hackberry is the dense proliferation of short stems that sprout from a common point. That hasn't happened with the Privet here.
These mites also cause curling of leaves; death/prematurely dropped leaves; stippling of leaves; and lots of other lousy landscape effects. They can have so many generations in a growing season, you will not believe it when you read it - though not nearly as many as the philanderingly fecund Spider Mites (who bust out 18-36).
So, toward a solution.
FIRST: take some samples of your Privet to your county's Cooperative Extension Service for plant pathogen diagnostic examination. If one of your plants is so far gone that you don't think it is recoverable, you could extract and take the whole plant to the CES and let them collect specimens/parts as they wish for examination. If you have a hand lens, or stronger magnification, take a look at leaves (top and bottom) and see if you can spot some of these miniscule insidious fiends.
SECOND: I would suggest
Stack24 lean in the direction mentioned: a horticultural oil or other less toxic approach, but aimed at nullifying mite activity. It usually takes a different category of pesticide to affect mites (miticides) than what works on other insects - because they are quite different organisms. I used to chuckle at a long-ago colleague's opinion that gardeners were actually FEEDING mites when they'd uselessly flail about with run-of-the-mill insecticides, because they were killing off competitive pests AND all the predatory beneficials which would slow down the mites.
I wish I personally had pictures of mites, but alas, I've never had that good of equipment to take that kind of excruciatingly clear closeups. I'd recommend as stimulating reading the exceptional tome
Insects That Feed On Trees And Shrubs by Warren T. Johnson and Howard H. Lyon (I have the 2nd Edition, since the late 1980s), where you can see and read about the predations of more insects/pests than you ever imagined existed in your worst landscape nightmares.