Azalea blackened and dying? - Ask Extension
We have noticed that the azaleas, planted on the north side of the house, have blackened stems and are in the process of dying. What is causing this ...
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Azalea blackened and dying? #650696
Asked June 14, 2020, 11:08 AM EDT
We have noticed that the azaleas, planted on the north side of the house, have blackened stems and are in the process of dying. What is causing this and what, if anything, can be done? We are in Grand Haven.
Steve McKenney
Ottawa County Michigan
Expert Response
Hi Steve,
Thank you for the photos. What I am seeing in the photos is suggestive of Azalea Bark Scale Eriococcus azaleae. There is treatment for it and you will need to be persistent. I ruled out mites as I did not see any webbing in the photos.
Azeleas can be tricky to grow in our area. Without the right winter protection, proper soil pH and nutrition they can get stressed and become susceptible to pest and disease issues.
The following is a description of Azealea Bark Scale from a fact sheet written by Clemson University - link to website is below:
Various scales attack azaleas and rhododendrons, but one of the most common is azalea bark scale (Eriococcus azaleae). Scales are unusual insects. They vary in appearance depending on age, sex, and species. The adult female azalea bark scale is dark red with a long sucking mouthpart. It is hidden from view by the matted waxy threads of the egg sac that covers it. The egg sac is about 1/8 inch in length. Adult females are immobile and can usually be found feeding in the forks of branches and on twigs. The nymphs (immature forms called crawlers) move around for a short time before they settle and start feeding. Both adults and crawlers suck plant sap.
Scale is difficult to eradicate. Treatment for light infestations are to scrape the eggs sacs off the branches and prune off any branches that are heavily infested.
Applying chemicals for heavier infestations such as horticultural oil or a soil drench with imidaproclid; a systemic insecticide are an option providing there are no blooms on the bush that insects/pollinators would visit.
I am including a few links to resources that discuss Azalea Bark Scale and treatment options in detail:
https://www.canr.msu.edu/news/thin_azaleas_with_crusty_stems_may_have_azalea_bark_scale
https://hgic.clemson.edu/factsheet/azalea-rhododendron-insect-pests/
https://www.azaleas.org/problems/
I hope you find this information helpful. Thank you for using Ask an Expert.
Thank you for the photos. What I am seeing in the photos is suggestive of Azalea Bark Scale Eriococcus azaleae. There is treatment for it and you will need to be persistent. I ruled out mites as I did not see any webbing in the photos.
Azeleas can be tricky to grow in our area. Without the right winter protection, proper soil pH and nutrition they can get stressed and become susceptible to pest and disease issues.
The following is a description of Azealea Bark Scale from a fact sheet written by Clemson University - link to website is below:
Various scales attack azaleas and rhododendrons, but one of the most common is azalea bark scale (Eriococcus azaleae). Scales are unusual insects. They vary in appearance depending on age, sex, and species. The adult female azalea bark scale is dark red with a long sucking mouthpart. It is hidden from view by the matted waxy threads of the egg sac that covers it. The egg sac is about 1/8 inch in length. Adult females are immobile and can usually be found feeding in the forks of branches and on twigs. The nymphs (immature forms called crawlers) move around for a short time before they settle and start feeding. Both adults and crawlers suck plant sap.
Scale is difficult to eradicate. Treatment for light infestations are to scrape the eggs sacs off the branches and prune off any branches that are heavily infested.
Applying chemicals for heavier infestations such as horticultural oil or a soil drench with imidaproclid; a systemic insecticide are an option providing there are no blooms on the bush that insects/pollinators would visit.
I am including a few links to resources that discuss Azalea Bark Scale and treatment options in detail:
https://www.canr.msu.edu/news/thin_azaleas_with_crusty_stems_may_have_azalea_bark_scale
https://hgic.clemson.edu/factsheet/azalea-rhododendron-insect-pests/
https://www.azaleas.org/problems/
I hope you find this information helpful. Thank you for using Ask an Expert.
