I have a pivot of Ligustrum that has had issues for a couple of years with plants just dropping their leaves and dying. We've tried replacing, but it just keeps happening and is slowly spreading to the whole hedge. Even now in May in full bloom, they are dropping leaves, the flowers are turning brown instead of just dropping their petals. I've had advice of too much water, not enough water, etc. no one has a clue. There are small white dots on the trunks of the dying plants, but the upper branches are still viable (green under the skin). We live in So Cal. We have the same bushes on other parts of the yard and they are fine. These get full sun and regular water.