Some of my Indian Hawthorns are mysteriously dying. An established plant will suddenly appear dull and sick. Within less than 10 days, the leaves turn brown and the plant dies. The "attacks" are random. The affected plants are growing right beside other Hawthorns that don't become affected. All of the plants that have died line the sides of a narrow concrete walkway. I should mention that our home is in Florida, very close (within view), to the Gulf of Mexico.
We have had Hawthorns in our yard in various places for more than 20 years. Many of those old plants, growning in other places in the yard, are still flourishing. We haven't experienced any trouble with Hawthornes at all until about the last 3 years. What could I do to prevent the problem?