Azalea and Rhododendron Root Rot (Phytophthora): Prevention and Resistant Varieties

Slow dieback in azaleas/rhododendrons is usually Phytophthora root rot. The fungus is ubiquitous; good drainage and resistant cultivars are the best defense.

Susceptible

'Coral Bell', 'Snow', 'Hershey Red'.

Resistant

'White Gumpo', 'Formosa', 'Hinodegiri'. Rhododendron resistance varies—check Auburn University list.

Cultural Fixes

• Amend clay with composted bark (suppresses Phytophthora).
• Water deeply once/week (drying between prevents fungus).
• Fertilize organically (cottonseed meal in April).
• Refresh pine straw mulch annually.

Once limbs wilt and roll, prune out dead wood—recovery is unlikely.

Rhododendron wilt