Azaleas--losing one by one annual-Phytophthora root & crown rot?
We've been in house 15 years. Azaleas in front yard obviously established. Assume planted with house: 1951. Beginning about five years ago they began dying, plant by plant from the right to the left. Online research really suggests Phytophthora, but talking to a clerk at a gardening store, she didn't think that was a problem. Attributed it to too much water (although we have rarely watered--only in driest periods. If it can be judged from the attached photos, is my assumption reasonable? I am considering tearing out the remaining plant, putting down new soil and replacing azaleas with bush roses, which the NC ag extension site suggests are resistant. Any advice appreciated. I don't know where to go.
Montgomery County Maryland
This does not look like a disease. This looks like poor growing conditions and the plants are stressed. They look weak, thin, foliage is mall and red tinged, compacted soil, dry shade, etc.
Azaleas grow best in morning sun and afternoon shade in an acidic, moist, well drained soil. You can prune back the shrub by one third after flowering and prune dead wood. Scratch the branches with your fingernail and look for green tissue. If you see it, the branch is viable. It may be helpful to test your soil in the area. Results will give you pH and nutrient deficiencies. http://extension.umd.edu/hgic/soils/soil-testing
Fertilize with an acidic fertilizer according to soil test results.
Mulch with an organic mulch no thicker than several inches and keep away from the base of the stems. Water during dry periods. http://extension.umd.edu/learn/ipm-series-azaleas-and-rhododendrons-hg51
Roses require full sun to grow best and this does not sound like a good location. Roses are also susceptible to an insect pest called rose slugs. http://extension.umd.edu/hgic/soils/soil-testing
If you want to plant another species of plant in this location, you will have to match the site conditions to the plant and plan for mature height and width.