Updated: September 3, 2021
Symptoms Details Possible Causes
Leaf Yellowing Towards interior of plant Early Fall Coloration (normal)
  Iron or magnesium chlorosis High soil pH and nutrient deficiency
  Leaves may also have sooty mold (black coating) Azalea Bark Scale
  Brightly colored, yellow-orange spots Azalea Leaf Rust
Leaf Stippling (tiny spots) Whitish spots on upper surface of leaves; black spots on the lower leaf surface Lace Bugs
Leaf Mottling (irregular marks or blotches) Margins of leaves cup, lower leaves covered with honeydew, then sooty mold; flat, oval transparent insects on the lower leaf surface Azalea Whitefly
Leaf Distortion Swollen green or white puffy areas on newly expanded leaves or flowers Exobasidium Leaf and Flower Gall
  Leaves roll and droop Drought and water Stress
Leaves Eaten or Chewed Notching of leaf margins; interior leaves show most damage Black Vine Weevil
  Notches chewed in leaf margins Two-banded Japanese Weevil
  Branches or entire plants may be defoliated Azalea Caterpillar
Blotches on Leaves Blotch mines on leaves of azalea in May Azalea Leafminer
Spots on Leaves Visible on upper leaf surface Various Fungal Leaf Spots
Leaf Scorch Margins of leaves turn brown in winter or spring Winter Injury
White Coating on Leaves May be on upper and lower leaf surfaces Powdery Mildew
Flowers Affected Small, water-soaked spots enlarge rapidly, cause flowers to collapse and feel slimy Ovulinia Petal Blight
  Swollen areas on buds, flowers and petals Exobasidium Leaf and Flower Gall
Failure to Flower Sudden temperature drop in fall, unusually cold winters, or spring freeze Winter Injury
Branch Dieback Scattered dying branches Botryosphaeria Dieback
  Leaves on scattered branches wilt, roll and turn brown Phytophthora Dieback
  Wilting of leaves and twig dieback Rhododendron Borer
  Wilting terminals and dieback Rhododendron Stem Borer
Entire Plant Dies Early symptoms may include wilting, shoot dieback, Phytophthora Root Rot
  As above, result of larvae feeding on roots and crown Black Vine Weevil and Two-banded Japanese Weevil
  Plants recover after irrigation Drought and water Stress