Dying of well established trees and shrubs
We have had a series of well established shrubs and trees mysteriously die on us. The first was an established oak tree with a 6 inch diameter trunk, then a nearby 20 year old 8 foot high and wide Rhododendron and now a nearby 10 year old Korean Spice viburnum bush. All are in the same area, approximately 10-15 feet from each other. The dying plants are in areas that contain beds of well established pachysandra that show no signs of stress.The area is in partial sun and is generally well watered. The Korean Spice bush is adjacent to another that is doing very well. The first indication of trouble has been wilting leaves. The attached picture showing the Rhododendron on the right of the oak tree with the viburnum an the left. It was taken 3 years ago. Do you have any suggestions to diagnose or correct the problem to keep other adjacent plants from suffering?
Once the plants are dead it is difficult to make an accurate diagnosis. It is possible you were dealing with vole damage, drought, planting too deeply, too much moisture, mechanical root damage, etc. we cannot say for sure. A specific insect or disease issue would not have taken out different species of plants.
We like to see photos of the plants when they are starting to show signs and symptoms of decline. All you can with the other plants is monitor and keep well watered during dry periods, make sure mulch is no thicker than several inches and keep away from the base of the plants. Check for vole damage http://extension.umd.edu/hgic/voles