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 azalea diagnosis    leaves | twigs | flowers | plant | related pages


Azaleas are generally healthy plants when their basic cultural requirements are met. However, they are subject to a number of problems caused by infectious agents, insect pests, weather and nutrition deficiencies. This table, organized by the major part of the plant affected, may help determine the cause of the problem.

 aid to diagnosis*

Symptoms
Disease or Pathogen
I. Leaves Affected
A. Leaves with definite brown areas
1.Localized brown or red-brown spots  Leaf spots
2.Browning of leaves at edges and near tips  Winter injury
3.Brown areas turning white with small black dots  Pestalotia leaf spot
B. Leaves off-color
1.Leaves off-color with white, powdery coating  Powdery mildew
2.New growth chlorotic or yellow  Nutrient deficiencies
Leaf and flower gall
 (Exobasidium)
3.Yellowish mottling on upper side of leaves; rolling of margins; flat, oval, transparent insects evident on bottom side of leaves  Whitefly
4.Whitish specks on upper surface of leaves; sticky spots on lower surface of leaves  Lace bugs
5.Leaves off-color; loss of vigor; no insects evident on foliage  Root problems
6.Leaves off-color; small "insects" evident on foliage  Mites
C.Leaves eaten or chewed at margins in half-circle pattern   Black vine weevil
D. Leaves distorted
1.Leaves thickened or fleshy, turn pale green or whitish  Leaf and flower gall
 (Exobasidium)
2.Leaves roll and droop; no insects evident  Water stress
Canker
Root problems
II. Branches and Twigs Affected
A. Terminal buds and leaves turn brown
1.Stem shrivels and definite canker forms; leaves roll and droop  Phytophthora dieback
Phytophthora syringae blight
2.Cankered area is rough from protruding bodies of fungus; edges of leaves may be affected first, and then entire leaves turn brown  Botyrosphaeria dieback
Phomopsis dieback
B.Ends of branches die; borer in stem tissue; yellow-white larvae about 1.3 cm long; small, black adults with three yellow transverse stripes on abdomen    Rhododendron borer
C.Buds and twigs affected; primarily on azaleas, buds and twigs killed    Bud and twig blight
 (Briosia)
III. Flowers affected
A.Flowers thickened or fleshy with gall-like appearance  Leaf and flower gall
 (Exobasidium)
B.Flowers water-soaked, collapsed    Ovulinia petal blight
IV. Entire plants affected
A.Plants become thin, wilt, and eventually die; major portion of root may be dead    Crown rot or wilt
 (Phytophthora)
Crown gall
 (Agrobacterium)
Cylindrocladium blight
B.Plants wilt and die suddenly; bark chewed from roots and basal stems    Black vine weevil grubs
c.Plants with poor color; definite, easily removed growths on stems and petioles  Scale insects
__________
* Reprinted by permission from Compendium of Rhododendron and Azalea Diseases, 1986, ISBN 0-89054-075-6, published by the American Phytopathological Society.
 related pages
azalea problems (parent page)

Updated July 20, 2007

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