Sick Azaleas

catcApril 16, 2007

I just moved into my house, so this is my first spring in the new place. We have a big clump of azaleas (at least two, maybe three different kinds)next to the garage, between the driveway and a brick retaining wall. There is something wrong with all of the plants and I'm not sure what it is. The foliage on all of the plants is small and underdeveloped, and the leaves look 'frosted'. As new growth comes out, it looks OK initially, then it starts turning white. The edges and ends of the leaves usually retain some color. Is this some kind of fungus? Maybe a problem with the soil? It could be too alkaline since they are next to pavement and masonry that could be leaching lime into the soil. Also, the plants are very leggy and could use a good pruning. Do I need to treat whatever this is before I prune?

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Embothrium(USDA 8 Sunset 5 WA)

Take affected twigs with foliage to local Extension office or other information source, find out what is going on and deal with that before whacking back. Maybe if you get them into better condition they won't look so leggy afterward, not need to be cut down.

    Bookmark   April 17, 2007 at 12:07AM
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luis_pr(7b/8a Hurst, TX)

I too would fix the frosted look problem before pruning. If your leaves look something like the leaf in this link then your azalea might be suffering from powdery mildew. Suggestion: If you take samples anywhere, please put leaves in sealed plastic bags so you will not spread diseases or insects elsewhere.

To determine if your soil is alkaline, you can either order a soil test or use one of those cheapo kits sold at nurseries and HD/Lowes. The kits will not be as accurate as those in a soil test but it will be "close" enough. You want to see PH Level numbers around 4.5 to 6.0 (although some azaleas are known to tolerate numbers higher than 6.0).

Too much shade can result is leggy plants whereas some plants are just naturally that way so:

1. If your plants receive little sun then consider re-planting elsewhere.
2. If your plants already receive part sun (2-3 hrs of sun) and are not naturally supposed to be leggy, try pinching the new leaf buds as they begin to elongate and unfurl this time of the year. This forces shoots to develop from dormant eyes in the lower leaf axils thereby creating a fuller looking plant. Repeat this procedure the next two years (three max). If the bush looses its shape after that, repeat the procedure in the affected area only.
3. If your plants already receive part sun (2-3 hrs of sun) and are normally supposed to be leggy, then prune them to an appropriate shape.
4. For information on pruning azaleas, click on
this link.


    Bookmark   April 17, 2007 at 3:46AM
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Thanks so much for the help. I think I may have solved at least part of the mystery. I took a closer look at some of the new growth and discovered that the backs of the leaves were covered with little black insects that look like aphids. Do aphids come in black? I've never seen anything but the green ones. I knew the New England pests, but North Carolina is throwing some new ones at me. If anyone knows what these bugs might be, or how best to get rid of them, I'd love to hear from you. I am going to test the soil, since I still think that there may be a ph problem. Is commercial fertilizer (Muracid, or similar) the best way to re-acidify the soil if that turns out to be an issue?

    Bookmark   April 17, 2007 at 7:34PM
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luis_pr(7b/8a Hurst, TX)

If it is an aphid infestation, you should notice that the leaves will curl, twist or fold. Aphids excrete a honeydew solution that covers the underside of leaves and which can grow fungi. You can use beneficial insects (ladybuds, praying manthis, etc) to fight off the aphids or you can use an insecticide like Orthene.

To verify if you have a ph problem, you can use one of those cheap kits sold at HD/Lowes or do a formal soil test with your Extension Service. If you have never done a formal soil test, I suggest you do one (every 3-5 years). In the test results, they will indicate IF you need to acidify the soil and how. Using commercial fertilizers is not the way to do it since they were not developed for that purpose. Products containing "elemental sulphur", "garden sulphur", "flowers of sulphur", iron sulphate and ammonium sulphate in the label are some examples. Products with aluminum sulphate are toxic to azaleas and should not be used to acidify their soil. Just wait until you receive the test results and go over the recommendations that they will send you (what to use and how much).


    Bookmark   April 18, 2007 at 9:28AM
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Well, I've identified the bugs - looks like immature Azalea lace bugs. The link below is a good reference for pests that like azaleas.

Here is a link that might be useful: Azalea Insect Pests

    Bookmark   April 18, 2007 at 10:24AM
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luis_pr(7b/8a Hurst, TX)

Great! That pest is very common this time of the year as late March to early April is when the eggs begin to hatch here in Texas. I am currently battling my annual infestation but most of "my" lace bugs are adults.

They look something like this. The immature bugs are indeed black while the adult ones are kind of yellowish/brown with almost transparent wings. However, they tend to hide under the leaves where they suck liquids (chlorophyll) from the leaves and give the top of the leaves a mottled greenish white look (or "frosted" as you said earlier).

You can fight these off with beneficial insects like lady bugs and praying manthis. Chemical insecticides will also work but they are not selective and will kill beneficial insects: spray the leaf undersides with Orthene, Malathion or Cygon and repeat the application every 10 days until the lacebug infestation is brought under control. You can also use a systemic fertilizer (a combination fertilizer and insecticide that the plant absorbs) such as Ferti-lome's Azalea Evergreen Food before this hatching time of the year sets in.

It should be easy to control these guys with the above methods. Every year, I get lace bugs in late March to early April on my azaleas followed by aphids some time in May on my roses. Oh, joy! At least I get no Japanese Beetles.


    Bookmark   April 19, 2007 at 4:09AM
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