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Common Azalea Problems, Pests, and Diseases (And How to Treat Them)

For the most part, Azaleas are relatively easy to maintain and have few problems if they have ideal growing conditions. This includes plenty of airflow, slightly acidic soil and adequate water and nutrition.

I’ve been growing azaleas for years and haven’t had any issues that have caused the demise of my plants.

In fact, the azalea that I currently have in my garden, which I propagated from a cutting, is healthy and thriving and put on an amazing floral display in spring.

In saying that, there are a few problems that can be faced by azalea growers. In this guide, I cover the most common ones and how you can treat and avoid them.

Powdery mildew on Azaleas

Powdery mildew | Plant care

Powdery mildew is a fungal disease that exhibits as a white powdery substance on the leaves.

Although I’ve had problems with powdery mildew on my vegetables such as zucchinis and pumpkins, I’ve been fortunate enough to never notice it on my azalea which is growing nearby. 

However, if you do come across powdery mildew on your azaleas, be aware that this is one of those fungal diseases that are quite difficult to control, especially in warm and humid weather. 

How to treat powdery mildew

As mentioned, this one is hard to treat. You can try spraying the plant with a copper-based fungicide. Some gardeners have also used a combination spray made with milk and water to get on top of this disease.

However, one of the best things you can do is remove the affected foliage as soon as you see it. This will effectively stop the spread of the disease.

How to avoid

It’s important that your azaleas are growing in full sun and that there is plenty of airflow around the plants. Nice healthy plants have better disease resistance too.

Additionally, you should only water your plants at the root level and avoid getting the leaves wet.

Azalea Lace Bug

Lace Bug | Plant care

These sap-sucking insects generally hide on the undersides of the leaves where they lay their eggs. An infestation of these tiny insects results in black spots on the leaves.

How to treat a lace bug infestation

If you notice these bugs on your azalea, you can treat them with an oil-based spray such as neem oil. However, even though this will kill the adult bugs, it won’t get rid of the eggs that they’ve already laid.

This means that you’ll have to spray continuously until there are no more eggs that can hatch.

A better option is to use a systemic treatment in late winter to early spring. As the plant leaves absorb the spray, this will be passed onto the insects that feed on the leaves and they will die.

One such product is Bug Killa Granular Garden Insecticide which is made by Richgro. This product also includes iron which is great for healthy plants. The granules are scattered over the soil around your plants and then watered in. It can also be used on pot plants.

Bear in mind though, that these insecticides may also harm important pollinators such as bees.

How to avoid

Although you might not be able to totally avoid an infestation from lace bugs, keeping your plants healthy and thriving will certainly help. Consider watering your plants with a liquid seaweed mixture during spring, summer and autumn. 

It’s also a good idea to mulch around your plants in order to keep the soil cool and retain moisture. This means that your plants will be less stressed on hot days.

Azalea Petal Blight

Azalea Petal Blight is another common fungal disease but it only affects the flowers causing them to turn brown and fall off the plant. Similar to powdery mildew, this disease is most active when weather conditions are warm and humid.

How to treat petal blight

You can spray your plants with a fungicide such as Searles Mancozeb Plus. Spray this all over the entire plant after you’ve removed the affected flowers and put them in the bin. You might need to reapply after 10 days to get rid of the disease.

How to avoid

Like all diseases, having a healthy plant will help to avoid problems. You also want to make sure that you only water the soil at the base of the plant and avoid getting any water on the flower buds or petals.

If your plant has been affected by this disease previously, make sure that you remove any flowers that have dropped to the ground and put them in the bin. This will stop the fungal spores from overwintering in the soil and infecting your plant the following spring.

Two Spotted Mite (Red Spider Mite)

Spider mites on rose leaf | Plant care

Red Spider Mites are also sap-suckers and cause mottling or greying of the leaves, especially the undersides.

I had this problem with an azalea in my last garden and although the leaves look a little unsightly, it will not kill your plant. The damaged leaves will eventually fall off and new ones will appear in spring.

How to treat two-spotted mite

You can spray your azalea with an oil-based fungicide to get rid of the mites but the leaves that have been affected will not recover. Therefore, it’s much better to remove the affected foliage and bin it.

How to avoid

Make sure your azalea is nice and healthy and receives a good dose of fertiliser in spring. 

Photo of author

Annette Hird

Annette Hird is a gardening expert with many years of experience in a range of gardening related positions. She has an Associate Diploma of Applied Science in Horticulture and has worked in a variety of production nurseries, primarily as a propagator. She has also been responsible for a large homestead garden that included lawn care, fruit trees, roses and many other ornamental plants. More recently, Annette has concentrated on improving the garden landscape of the homes that she has lived in and focused a lot of energy on growing edible plants as well. She now enjoys sharing her experience and knowledge with others by writing articles about all facets of gardening and growing plants.

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