WSU Extension

Hortsense

Azalea
 
Disease
Botrytis petal blight 
Cylindrocladium blight & root rot 
Leaf and flower gall 
Leaf spot 
Lime-induced chlorosis 
Marginal leaf necrosis 
Nematode (stunt) 
Ovulinia petal blight 
Powdery mildew 
Root rot (Phytophthora) 
Insect
Azalea bark scale 
Azalea lace bug 
Azalea leafminer 
Obliquebanded leafroller 
Root weevils 
Spider mites 



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Caption: Root weevil larval damage
Photo by: A.L. Antonelli
  
Azalea : Root weevils
(revision date: 3/10/2017)


Biology
Characteristic damage includes notching of leaf edges by adults and minor to severe root and bark damage by larvae. Azaleas generally have less severe leaf notching than rhododendrons, but may be damaged or killed by root weevils feeding on lower stems and roots. Occasionally the trunk is girdled at or just below the soil surface. Adults are wingless and begin feeding around June to August, depending on the species.
Management Options


Non-Chemical Management
  • Hand-pick and kill night-feeding adults.
  • Apply beneficial nematodes which kill the larvae. They are used as a soil drench in moist soils over 52 F (late summer to early fall in western Washington). Read and follow the label directions carefully.
Select non-chemical management options as your first choice!

Chemical Management

Apply when first signs of notching on new leaves are noticed. Monthly applications may be needed if infestation is heavy. Cease when first hard frost occurs in late fall/early winter. Night applications are more effective. Beneficial nematodes can be ordered through certain nurseries. They can be applied to control the larval stage if soil temperatures are warmer than 52 F. Do not apply nematodes in direct sunlight and make sure the soil is saturated with water prior to application.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.
  • Bonide Systemic Insect Control
    Active ingredient: acephate  |  EPA reg no: 239-2461-4
  • Naturalis L
    Active ingredient: Beauveria bassiana  |  EPA reg no: 53871-9
  • Safer Brand BioNEEM Multi-Purpose Insecticide & Repellent Conc [Organic]
    Active ingredient: azadirachtin  |  EPA reg no: 70051-6-42697
  • This list may not include all products registered for this use.
Images

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Caption: Root weevil larval damage
Photo by: A.L. Antonelli
Caption: Adult root weevil damage
Photo by: E.P. Breakey
Caption: Root weevil larvae
Photo by: A.L. Antonelli