Problems with Ilex vomitoria 'Schilling's Dwarf'
My dwarf hollies keep losing leaves. Large sections of the shrubs are defoliated. They produce a new crop of new leaves but these drop soon too. I can brush my hand against them and watch new green leaves falling. Some of the leaves have black spots. I have seen a few nibbled by insects, but most are spotted. My hollies have suffered in the past from limb die back, but they recovered and eventually regain their shape. I don't know if this is the beginning of the same problem.
I called the extension agent and she said my hollies are suffering from a very serious fungal infection. She warned me that It would spread to all of the hollies in the garden unless I pulled up the infected plants and threw them away. She spoke as though chances of recovery are very low.
I'm doubtful though. There are many, many "Schilling's dwarfs" in my town and I don't believe I've ever seen a well established one die, though I have seen many with bare spots from limb die back and other problems.
I have tried spraying with a neem and Castile soap spray, but it did little good.
The shrubs are located in a mostly full sun location on high dry sand. Other schillings growing under the same conditions are doing very well. A grouping of them in the corner of the garden are the only ones affected so far.
Does anyone out there know what is the problem with my hollies? Is there any fungicide or other treatment that could help them to keep their leaves? The extension said there were none. But I would like to save them and keep them looking their best if possible.