Why did my rhododendron wilt and die?

Rhododendrons and azaleas are susceptible to a fungal wilt disease called Phytophthora root rot.  The Phytophthora fungus enters the roots of the plant from infested soil and clogs the water-conducting vessels of the plant.  Symptoms include poor growth, rolling of leaves, and the eventual death of the plant.  Cutting into the base of the plant reveals reddish-brown discoloration below the bark.

Wet, poorly drained soils favor infection by the Phytophthora fungus.  Phytophthora root rot can be avoided by planting rhododendrons and azaleas in well-drained soils.  Also, don't water too frequently in dry weather.  A thorough watering every 7 to 10 days should be adequate for established rhododendrons and azaleas during dry periods.  Dead or dying plants should be removed completely, along with the soil around the roots, to remove as much of the fungus as possible.