Dead Branches on Azaleas

bevingaMarch 16, 2007


When we bought our house a couple of years ago, we inherited a beautifully landscaped yard; however, it had been neglected for a couple of years. There are quite a lot of azaleas in the front, on the sides, and around back, and all look to have been established probably 10-15 years ago. They bloom, profusely, each spring.

As I began trying to get the yard back to its original beauty, I found that many azaleas had dead branches, so I pruned them out. That was three falls ago. Now, for the past two springs, I have found that although I pruned all the dead branches in the fall, there seems to be more.

What could be causing these branches to die? There are so very many azaleas that I'm not sure how to go about fertilizing them, if that is needed. Do you have any advice as to what I should do to keep these branches from continuing to die?

Thanks for any advice you can offer!


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morz8(Washington Coast Z8b)

There are a few things that could cause the results you are describing, but low fertility isn't one of them.

Easiest to address would be drought - inadequate watering. An azalea under stress from drought may die, or just individual branches or sections of the plant may die.

Bark split - caused by an early out-of-nowhere hard frost in Fall , or a late spring frost that follows a period of warmer weather. This type of weather damage can often go unnoticed, hidden by foliage until branches begin to die in Summer. While possible, I wouldn't think in Z7 this would be an every year occurrence

Azalea Dieback -Phomopsis, a fungal infection.

Rhododendron Borer, Adults appear in May/June and lay eggs on the twigs. Upon hatching, small caterpillars bore into the inner bark of the main stems and branches; growth above them dies.

    Bookmark   March 17, 2007 at 3:18PM
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rhodyman(SE PA, USDA Z6)

Morz8 is right on with his recommendations. I will expand the description a little:

Prolonged drought weakens plants and often results in the appearance of fungal cankers on the branches of older azaleas. Look for branches that wilt in hot, dry weather in late summer and be sure to water azaleas if drought drags on more than a few weeks. Prune out the affected branches to stop the spread of fungal canker diseases.

Azalea Dieback is caused by the fungus Phomopsis rhododendri. Typically, dying branches (stem dieback) begin to appear on an otherwise healthy plant. The leaves die and can remain attached to the plant until late summer. Usually a single branch on an established plant is affected. Scraping away the bark with a knife reveals discolored wood under the bark that appears chocolate brown. Dieback is difficult to control on azaleas in the landscape. The azalea varieties that are the least susceptible include: 'Delaware Valley White,' 'Hershey Red,' 'Pink Gumpo' and 'Snow.' Reduce stress to the plants by planting in partial shade and watering during dry periods. Avoid wounding the plant. Prune infected branches well below all discolored wood and dispose of dead plant material. Clean pruning tools between cuts with a dilute solution of household bleach (1 part bleach to 9 parts water).

Borers are easy to diagnose. The dead branch is hollow near where it meets the live branch.

Bark split is easy to see if you look in the right place. It is usually near where the plant comes out of the ground and usually affects one the entire plant or an entire branch from the ground up.

A fifth cause is the normal natural trimming a plant does of interior branches that don't receive enough light.

    Bookmark   March 17, 2007 at 8:04PM
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Thank you for your wonderful explanation! I am still trying to figure out how to post pictures on here so I can show you exactly to what I'm referring, although I am sure you already know. I have a couple of additional questions, though.

You said that dieback is difficult to control on azaleas in a landscape. All of my azaleas are well established, but today, I was out looking at them and found that a whole lot of them have the dead branches. I pruned some of the dead branches, but now what do I need to do to keep this from traveling to my healthy azaleas?

I also bought two 5-gal. sized Encore azaleas, Autumn Angel and Autumn Belle. If I plant them where I've had to remove whole plants, will they become infected? What should I do to protect them from this fungus? They are extremely healthy looking right now.

Also, what causes this fungus?

Thanks for being so patient with me...I googled the fungus and found your site. You are doing a great service to many!


    Bookmark   March 28, 2007 at 8:29PM
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rhodyman(SE PA, USDA Z6)

The dieback fungus is agrivated by drought. Sanitation (removing all dead wood and either burning it or having removed with the trash) is the main prevention. To much moisture will cause a different fungus that kills the roots. So it is important to keep the roots from drying out, but to keep them from staying too wet. Good drainage is essential.

I had a lot of dieback this winter, but I am not concerned. The plants were healthy but apparently the warm weather we had this winter kept them from going dormant made them use more moisture than was available in the soil. I will cut back and destroy the dead branches. Occasional pruning helps a plant.

Always remember that azaleas have shallow roots so they dry out more quickly but also are susceptible to damage if the ground is cultivated and don't like to compete with the roots of other plants. They need a good mulch to protect the roots.

    Bookmark   March 28, 2007 at 10:58PM
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