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Azaleas are one of the most popular spring-flowering plants in gardens. While these lovely plants are normally resilient and trouble-free, they are occasionally affected by pests and diseases.
In this article, we will explore the most widespread diseases and pests that infest azalea plants, as well as how to deal with them if you come across one.
Most Common Azalea Diseases & Pests
Below are some of the most common azalea plant pests and diseases which include the following:
1. Azalea Bark Scale
This azalea plant pest is most common in the eastern United States. They are a form of soft scale, and an infestation can be noticed by clear sticky honeydew which is usually on the leaves or stems, as well as sooty mold (black fungus), yellowing of leaves, and twig dieback.
This scale is best noticeable from May to June when white egg sacs can be found in twig forks.
However, overwintering immature scales also seen as nymphs are less than 18-inch length, gray, and commonly found in twig forks.
A. Azaleas may withstand modest populations of this bark scale without suffering any significant harm. However, if there are no yellowing leaves, then no treatment will be required.
B. To inhibit population growth, consider removing hands by squeezing the scales.
C. Beneficial predators and parasites are another technique that will generally manage minor bark scale infestations.
D. Furthermore, it is important that you inspect egg sacs for holes that suggest parasitoid control, and keep an eye out for predators like ladybird beetles.
2. Azalea Lace Bug
- Azalea lace bugs (Stephanitis pyriodes) are one of the most common pests of Azalea bushes. Infected plants may have yellow to pale foliage with black bugs on the undersides of the leaves in large numbers.
- Lace bug damage is visible as stippling (extremely small dots) on the leaves of plants growing in humid areas with minimal plant variety. Damage often emerges on old leaves in early May and later on new growth. On the undersides of stippled leaves, black fecal stains will appear.
Lace insect infestations can cause leaves to become yellow and ultimately brown. Shrubs that are extensively infected and exposed to the full sun may be destroyed.
Lace bugs have numerous generations every year. Each azalea, rhododendron, and Japanese andromeda (Pieris japonica) has its own species of lace insect.
Insecticidal soap is usually effective in controlling lace bugs in late spring or fall.
A. Plant azaleas in partial sun (morning sun and afternoon shade). Mulch with chopped oak leaves, leaf mold, or pine needles and water deeply during drought periods. Stressed plants are more susceptible to lace bug feeding.
B. Natural enemies and predacious beetles feed on lace bugs. They can keep small populations of lace bugs under control. Do not spray if you find beneficial insects feeding on the lace bugs.
C. Look for nymphs and black fecal spots on lower leaf surfaces in early May to estimate potentially damaging populations.
D. When lace bug populations are high, sprays of horticultural oil (at a 2% summer rate) or insecticidal soap will control lace bugs if the lower surfaces of the leaves where lace bugs are active are thoroughly covered.
E. Currently registered systemic insecticide may be necessary where coverage of the undersides of leaves is difficult.
Read Also: When Do Azaleas Bloom?
3. Azalea Leafminers
This azalea plant pest mines between the top and lower surfaces of the leaves, creating brown blisters or yellowing. Azalea leafminers can cause affected leaves to curl and droop.
Beginning in May, the development of blotch mines in azalea leaves indicates azalea leafminer (Caloptilia azaleella) damage.
They feast between the top and lower leaf surfaces causing mines to develop along the midrib.
Also, as the larvae develop, they use silk to curl the ends of the leaves and feed inside the curl. Huge populations induce leaf browning and untimely drop.
Rake and discard fallen or damaged leaves in the fall to eliminate pupae that have overwintered.
4. Azalea Caterpillars
These azalea pests range in color from reddish to brownish black, with white and yellow stripes. Azalea caterpillars may swiftly defoliate bushes when they feed in clusters.
They are black with rows of white or pale yellow dots, reddish-brown legs, head, and neck region, and measure 2 1/2 inches when grown. Defoliation can occur on individual branches or on whole plants thereby damage happens in the late summer and fall.
A. When there is biting damage, look for caterpillars. Pick off the caterpillars by hand if there are only a few of them.
B. If manual removal is not possible, spray bushes with Bacillus thuringiensis (Bt), a microbial pesticide that is specialized for juvenile caterpillars and is available under a variety of brand names.
C. Insecticidal soap is another option. When caterpillars are plentiful and immature (less than 3/4 inch long), use either spray. Spinosad, a biorational insecticide (the least harmful type), may also be used on both young and elderly caterpillars.
5. Azalea Whitefly
This whitefly (Pealius azaleas) is often found only on azalea types with hairy leaves. Adults and nymphs of whiteflies feed on the underside of the leaf.
There are severe infestations cause the terminal leaf edges to cup. These diseased leaves will ultimately turn yellow and wilt. Honeydew covers the leaves, followed by sooty mold (a black coating).
A. If the infestation is mild and there are few or no plant symptoms, and if beneficial insects are present, spray the undersides of leaves with insecticidal soap or horticultural oil at the summer rate of 2%.
B. Active lady beetle adults or larvae, lacewing larvae, or parasitoids evidenced by tiny circular holes on young whiteflies can all be signs of helpful insects which can be used to get rid of the pests.
6. Phytophthora Dieback
While uncommon in the landscape, is a separate phase of the Phytophthora disease syndrome affecting rhododendrons, azaleas, leucothoe, and Japanese andromeda (Pieris japonica).
It can be spread through the environment by infected plants and can be particularly damaging to plants planted with overhead sprinkler watering. The pathogen causes sickness when it is spilled upon the leaves.
7. Powdery Mildew
Compared to evergreen plants, deciduous azaleas are more vulnerable to powdery mildew. It has the greatest impact on young plants grown in dense shade.
Infected plants appear to have a powdery white coating on their leaves. The disease is still most severe during chilly, damp conditions.
These fungi develop spores on the surface of diseased leaves, which are spread by wind currents to surrounding leaf tissue and tend to overwinter in the bud scales, ready to infect the plant the next season.
Keep sufficient plant spacing to ensure proper air circulation. Horticultural oil products and powdery mildew fungicides are registered.
1. What Are The Most Common Azalea Diseases?
There are several diseases that commonly occur on rhododendrons and azaleas in landscapes and nurseries every year in Connecticut.
These include fungal leaf spots, leaf and flower gall, root rot, oedema, leaf flooding, winter injury, and chlorosis.
2. What Are The Problems With The Azalea Plant?
The fungus Phytophthora species causes one of the most common disease problems in the landscape for rhododendron and azalea.
This fungus is a “water mold,” and thrives in poorly drained or wet conditions. A wilted plant is usually the first sign of trouble. Rhododendron leaves will curl inward and droop.
3. How Do You Treat Azalea Disease?
Especially, while treating Leaf Spots on Azaleas, you should try to clear out infected leaves, mulch around the base, focus on roots when watering and keep an eye on the soil PH level.
If worst comes to worst, use fungicides like Copper Hydroxide, Thiophanate-methyl, or Chlorothalonil.
4. What Is The Best Insecticide For Azaleas?
For long-lasting preventive control use a soil-applied systemic treatment such as imidacloprid (Bayer Tree and Shrub Insect Control) or dinotefuran (Greenlight Tree and Shrub Insect Control).
For the best control of heavy infestations, apply a foliar spray of acephate and a soil treatment of imidacloprid or dinotefuran.
5. What Causes Azaleas To Start Dying?
Fungal diseases can strike azaleas and cause browning leaf margins and other symptoms. Dieback, a fungal disease triggered by stress, causes foliage to wilt and yellow and twigs and branches to die.
If you see brown streaks on the cut stem, this is the problem.
6. What Is The Fungal Disease Of Azaleas?
Azalea gall is a very distinctive and curious-looking disease; Galls vary in size from that of a pea to a small plum form on the leaves or flowers.
The leaf or flower involved is practically replaced by the fleshy irregular gall. Galls are at first pale green, or very rarely reddish.
7. What Does An Unhealthy Azalea Look Like?
The leaves become curled, fleshy, and pale green to white. Affected leaves eventually turn brown and should be removed and destroyed.
No plant can survive without encountering problems such as pest and disease infestations at some time each year. What matters is having a proper understanding of how to manage any of them when they arise.
Having said that, we believe that this article has opened your eyes to the various diseases and pests that can harm your azalea and how to deal with them.
If you have any questions or recommendations, please leave them in the comments box below.