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: ALB damage and tar spots on azalea
Photo by: J. Glass
  
Azalea : Azalea lace bug
(revision date: 2/14/2019)


Biology
Azalea lace bug (Stephanitis pyrioides) is a relatively new insect pest in the Pacific Northwest. Unlike rhododendron lace bug (S. rhododendri), azalea lace bug attacks both azaleas and rhododendrons and may cause significant damage on both. Both adults and nymphs feed on the underside of leaves. Symptoms of damage are stippling, bleaching, or a silvery or yellowish (chlorotic) appearance of the leaves. The underside of the leaf will appear dirty due to the presence of insects (eggs, nymphs, and adults) and brownish or tar-like fecal spots, particularly along the leaf veins. Heavily damaged leaves may drop from the plant. Adults are about 1/10 inch long with lacy, net-like, transparent wings. The azalea lace bug has smoky, brown markings on the wings, which distinguish it from the pale whitish-tan rhododendron lace bug. The young nymph is colorless to black and spiny depending on age. The first generation of nymphs emerges in spring after frost danger has passed. Several generations may occur in a year. Since these insects overwinter as eggs laid on the leaves, evergreen varieties are most susceptible. Plants in full sun or suffering from drought may suffer greater damage. Damaged leaves do not recover, so early detection is important. See also Rhododendron: Rhododendron lace bug.
Management Options


Non-Chemical Management
  • Maintain plant health by providing proper water and nutrition. Stressed plants are more susceptible to insect damage.
  • Hosing plants with a strong stream of water directed at the underside of leaves will help to remove them, and wingless nymphs will not return.
  • Grow azaleas in shady areas to minimize damage.
  • Avoid use of broad-spectrum insecticides to preserve populations of beneficial predators which will help control lace bugs.
Select non-chemical management options as your first choice!

Chemical Management

Unless the product you select is systemic and absorbed into the leaf tissues, applications should be directed to undersides of leaves. Thorough coverage is essential. Insecticidal soaps may require repeat applications (about 2-week intervals) for effective control. Follow label instructions for products applied as a drench. Apply in spring when nymphs appear. These insects are difficult to control with one application. Avoid using acephate, bifenthrin, cyfluthrin or imidacloprid on blooming plants or if there is any possibility of pesticide drift onto blooming plants nearby, as these products are toxic to bees.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.
  • Bayer Advanced Power Force Multi-Insect Killer R-T-S
    Active ingredient: cyfluthrin  |  EPA reg no: 72155-39
  • Bonide Systemic Insect Control
    Active ingredient: acephate  |  EPA reg no: 239-2461-4
  • Bull's-Eye Bioinsecticide
    Active ingredient: spinosad (spinosyn A+D)  |  EPA reg no: 62719-314-56872
  • Monterey Garden Insect Spray [Organic]
    Active ingredient: spinosad (spinosyn A+D)  |  EPA reg no: 62719-314-54705
  • R-T-U Year-Round Spray Oil
    Active ingredient: oil/pet distillate  |  EPA reg no: 6218-78
  • Safer Brand BioNEEM Multi-Purpose Insecticide & Repellent Conc [Organic]
    Active ingredient: azadirachtin  |  EPA reg no: 70051-6-42697
  • Safer Brand Insect Killing Soap Conc II [Organic]
    Active ingredient: potassium laurate  |  EPA reg no: 42697-60
  • This list may not include all products registered for this use.
Images

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Caption: ALB damage and tar spots on azalea
Photo by: J. Glass