Azalea Problems Identification - Ask Extension
Hello, I have been to your page http://extension.umd.edu/learn/ipm-series-azaleas-and-rhododendrons-hg51 regarding rhododendron and azalea problems. C...
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Azalea Problems Identification #449426
Asked April 24, 2018, 4:32 PM EDT
Hello, I have been to your page http://extension.umd.edu/learn/ipm-series-azaleas-and-rhododendrons-hg51 regarding rhododendron and azalea problems. Could you please help ensure I am correctly identifying what is wrong with these two azaleas? They were planted by a previous owner in compacted clay in heavy shade, close to the foundation of the house, with little space between them.
The first photo is of an azalea on which I can find no evidence of insects on the upper or undersides of the leaves. It seems to follow the pattern of having "yellow leaves with prominent green veins," which would indicate leaf chlorosis. Is this an accurate assessment?
The second and third photos depict an azalea that has grown right next to the "leaf chlorosis" azalea for several years. They are clearly different varieties. Is this second azalea afflicted by leaf rust, and if so, why does it not affect both varieties? Could chlorosis also cause the rust-like spotting, as both azaleas have been planted close to a brick wall and, I presume, a cement foundation?
Thank you,
Shannon Lyons, Kensington, MD
Montgomery County Maryland
Expert Response
Your azalea surely look stressed and are struggling. This could be caused by multiple issues- lack of light, nutritional problems, poor soil,
placement, etc.
The first photo does look like chlorosis, which is a nutrient deficiency. Other causes of chlorosis include poor root growth, root rot, root damage caused by over fertilization or excessive deep cultivation, soil nematodes and poor drainage.
We'd suggest a soil test of the area to give the best indication of pH and nutrients and what needs to be done. Here is our soil testing information: http://extension.umd.edu/hgic/soils/soil-testing
The other photos seems to show secondary leaf spot diseases, which are not terribly uncommon and usually not fatal as healthy plants send out a flush of fresh new leaves- more than they need to to 'feed' themselves. They are more apt to show up on stressed plants however.
(We don't think it's rust) There are numerous leaf spotting diseases that occur on shrubs, but few are lethal.
As for what to do....
Start with a soil test. It doesn't take long, but while you wait you could give them a quick dose of Mir-Acid (like Miracle Gro but for acid loving plants) and see if you get a quick response of green up.
Otherwise, longer term, you should look treating with kelates while acting to acidifying the area with Holly-tone, or Ammonium sulfate (works faster). (think products like Espoma)
Next, just after flowering, you can prune to shape, or even reduce them in size.
How much light does the area get? While azaleas like shade, deep shade can make it a little more difficult and they will get rangy reaching for light. If you can selectively trim overhanging trees, do so.
cm
placement, etc.
The first photo does look like chlorosis, which is a nutrient deficiency. Other causes of chlorosis include poor root growth, root rot, root damage caused by over fertilization or excessive deep cultivation, soil nematodes and poor drainage.
We'd suggest a soil test of the area to give the best indication of pH and nutrients and what needs to be done. Here is our soil testing information: http://extension.umd.edu/hgic/soils/soil-testing
The other photos seems to show secondary leaf spot diseases, which are not terribly uncommon and usually not fatal as healthy plants send out a flush of fresh new leaves- more than they need to to 'feed' themselves. They are more apt to show up on stressed plants however.
(We don't think it's rust) There are numerous leaf spotting diseases that occur on shrubs, but few are lethal.
As for what to do....
Start with a soil test. It doesn't take long, but while you wait you could give them a quick dose of Mir-Acid (like Miracle Gro but for acid loving plants) and see if you get a quick response of green up.
Otherwise, longer term, you should look treating with kelates while acting to acidifying the area with Holly-tone, or Ammonium sulfate (works faster). (think products like Espoma)
Next, just after flowering, you can prune to shape, or even reduce them in size.
How much light does the area get? While azaleas like shade, deep shade can make it a little more difficult and they will get rangy reaching for light. If you can selectively trim overhanging trees, do so.
cm
