Azalea branch die off
Thank you for your help! We've had some challenges with the azalea bushes in the front of our house since we moved in four years ago. There are three definitely types of azalea bushes planted in this location. The one on the right has always seemed to do fine. The one on the left gave us more problems in prior years, but seems to be doing better this year. The middle one has always been problematic. What happens is that the leaves on a branch start to shrivel and this spreads to the rest of the branch until it all dies off. We prune these branches once we notice them dieing off. In the picture, you can see a large gap in the middle where one of the bushes has been struggling. A couple of years ago I started providing the azaleas with fertilizer designed for azaleas and this seemed to help quite a bit, but hasn't solved the problem. The bushes face east and get a lot of sun in the morning and early afternoon. They are located in a garden bed that is relatively flat, so I think they probably stay more moist for a while after it rains compared to many of our other garden beds.
Montgomery County Maryland
Overall, we think the azalea looks pretty good. In general, azaleas have a shallow root system and grow best in a moist well drained soil in morning sun and afternoon shade. You mentioned that the area is flat and may collect water. Perhaps you can grade this area so the water does not collect. Make sure there are no downspouts dumping water in the root zone.
The branch dieback may be due to a common fungal disease in rhododendrons/azaleas called Botrysphaeria canker. A typical symptom of this fungal disease is scattered dying branches on an otherwise healthy plant. The pathogen can infect all ages of stem tissue through wounds, pruning cuts, and leaf scars. Heat, drought stress, and winter injury can increase disease incidence. The recommended control is pruning back to healthy tissue. Plants should also be protected from rough treatment during maintenance activities to prevent unnecessary wounds.https://extension.umd.edu/hgic/topics/azaleas-and-rhododendrons-common-diseases-and-abiotic-problems
Fertilizer will not help unless there is a nutrient deficiency. It does not look like it but you can test the soil for pH and nutrient deficiencies. https://extension.umd.edu/hgic/topics/soil-testing
At this point check the drainage, make sure mulch is not excessive, and water during dry periods.
Very helpful again! I have some additional questions about other plants around our yard that I will submit.
You are welcome.