Sick Azaleas

kelkolkat(8)April 27, 2010

I think my Encore Azalea's are sick. We had a landscaping company plant them last fall. They looked great in the fall and even bloomed. Once spring got here I noticed the leaves looked yellow and had brown spots all over them. I asked a local gardener and he said it looked like they had been over or under watered and whatever we were doing to do the opposite. We really hadn't started a spring watering cycle since it's been raining some and not hot enough. So we watered a little longer each time. Right after this they bloomed in time for the Masters. Then the blooms pretty much fell off like suppose to. Now they just look leggy again and seem to not be doing good. In the neighborhoods I see them and the bushes are all thick and lush and mine look like sprigs with some leaves on them.

Can anyone help? Here are a few pictures to help.

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luis_pr(7b/8a Hurst, TX)

The spots lookd like some type of fungal infection. I would first try to limit it by watering the soil instead of watering the leaves. Then I would use the finger method to determine if you are watering correctly. Insert a finger to a depth of 4" and water 1 gallon of water when the soil feels dry or almost dry. Make a note in a calendar every time you water. After two weeks or so, review how often you water. Then set your sprinkler or dry irrigation to water 1 gallon of water on the same frequency that you watered manually (every 3/4/5 days). If your temperatures vary by 10-15 degrees and stay there, you can use the finger method to see if you have to tweak things. Pinching can help the shrubs produce fuller growth. The leggy look suggests that it may not have had enough sun when it was growing at the nursery (ie, too much shade). Pinch the leaves for 2-3 years as the the leaves begin to unfurl in Spring.

    Bookmark   April 29, 2010 at 12:48PM
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Ok I will try the hand watering approach first and see if that makes a difference. The local guy I walked to mentioned pinching them also. Just pinch the leaves off around the bottom parts of it? The tops have some new leaves that came on right before it bloomed but it's the bottoms that look so leggy. So you think this will get better over a length of time?

    Bookmark   April 29, 2010 at 1:34PM
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rhodyman(SE PA, USDA Z6)

Since it is only affecting a few leaves, it is probably a localized thing. Look at the undersides of the affected leaves. You may see some insects. Some possibilities are:

1) Powdery Mildew: Light green or yellowish patches on leaves sometimes accompanies by brown spots on the back side of leaves is a sign of Powdery Mildew (Microsphaera azaleae). One of the puzzling aspects of this fungal problem is the fact that two different affected plants vary in appearance. A deep green leaf may begin to show lighter green patches, and these areas will gradually become more yellow. Another cultivar may gets brownish purple spots on both tops and bottoms of leaves. This common disease is named Powdery Mildew despite how little the symptoms resemble the familiar fungal disease often seen on roses. Usually the disease doesn't produce the familiar white powder-like spores, although late in the summer some may become visible. The disease manifests instead as color changes in the leaves, followed by defoliation toward the end of the growing season. Many azaleas, if basically healthy, will coexist with the disease and seem to outgrow or at least survive the symptoms. Last year's leaves, once they have been hit by the disease, will always have it, with symptoms persisting from year to year until the leaves drop off. High relative humidity at night and low relative humidity during day with 70-80 F (22-27 C) temperatures is ideal for the disease to flourish.

2) Whitefly: Yellow mottling on the upper surface of leaves and black sooty mold and transparent insects on the bottom are symptoms of Azalea Whitefly (Pealius azaleae.) and Rhododendron Whitefly (Dialeurodes chittendeni.). They may also cause the following symptoms:
Small white spots on the underside of leaves and small white flies on under-surface of leaves is also an indication in infestation of Azalea Whitefly (Pealius azaleae.) and Rhododendron Whitefly (Dialeurodes chittendeni.). They are more prevalent on certain varieties and on plants grown in protected areas. These small white flying insects look like an aphid with wings and suck on the underside of foliage, leaving white spots where it has been. Heavy infestations cause the margins of terminal leaves to cup. These infested leaves will eventually turn yellowish and appear wilted. The lower leaves become covered with honeydew, followed by sooty mold (a black coating). To check for the presence of whiteflies, shake the terminals of white azaleas to flush out adult whiteflies which look like tiny white moths. Examine the lower surfaces of leaves for the presence of nymphs, which are flat, yellowish green, and resemble scale insects. All stages occur on the under sides of leaves. This whitefly is usually limited to varieties of the snow azalea, Rhododendron mucronatum. If the infestation is light, little or no plant symptoms are evident, and if beneficial insects are present, spray the undersides of leaves with insecticidal soap or a horticultural oil at the 2%summer rate. If the infestation is heavy use a registered residual insecticide such as Malathion, Diazinon or Orthene. Dick Murcott had a simple remedy to control the numbers of white flies. He would hang pieces of stiff plastic or 12" square metal sheets painted with a bright yellow/orange paint and then covered with petroleum jelly or any clear, sticky material. The white flies will fly to the colored material and get stuck in the sticky stuff!

Here is a link that might be useful: How to care for rhododendrons and azaleas.

    Bookmark   April 30, 2010 at 9:33AM
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Tomorrow I will take a closer look at the leaves underneath. I don't remember seeing anything like that on them but could have missed it. I'll try to post a picture of them once I look. Could that be why they look so leggy at the bottoms? It's like they have no bushiness to them. Even though this is my first time to have them I thought they were more full and like a bush. Do you agree with anything said about under or over watering?

    Bookmark   April 30, 2010 at 12:07PM
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rhodyman(SE PA, USDA Z6)

Some varieties are low and bushy. Yours are more upright and can be made to bush out by pruning soon after they bloom.

    Bookmark   May 4, 2010 at 11:32AM
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I looked at the plants this weekend. There are no white spots or bugs on the bottoms of them. Before I touched them I shooked all the plants to see if anythign would fly off from them and nothing. So what would be your next suggestions? I did the 4" finger test and the soil was moist, not wet not dry. I watered each of them to the root quite a bit but don't really see much difference as I am sure it takes a week or so of doing it. What do you think about putting those water nanny things down in the ground there and slow releasing water into them? I can't set out springlers to water more often because then it will water the whole yard like that and cause issues with the grass and our high humidity coming up. Any thoughts?

    Bookmark   May 6, 2010 at 9:35AM
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rhodyman(SE PA, USDA Z6)

They don't need water. To much water in warm weather will kill them. More azaleas are killed by watering than by drought. Wet soil causes root rot which is nearly always fatal.

The problem appears to be powdery mildew which is agrivated by moist conditions. If you haven't fertilized yet, you should use a small amount of Hollytone, about half the amount recommended on the package. Make sure you have at least 2 inches of mulch. They look well mulched, but I can't tell how much. There are a number of ways to manage this disease.

1) Do not overwater or overfertilize plants, as the fungus prefers succulent new growth.
2) Hand-pick and destroy mildewed leaves to control small amounts of infection.
3) Hose diseased plants with water in the AM when practical. This can help remove fungus and prevent new infections.
4) Prune and space plantings to allow good air circulation. Do not plant in extremely shaded or damp areas.
5) Rake and destroy fallen leaves year-round to reduce infection source. Do not compost diseased materials.

Chemical control is possible, but it will only prevent the spread and not turn diseased leaves green. Begin applications when you first notice the disease on current-year leaves. Some products labeled for powdery mildew on azaleas include:

Bonide Remedy
Monterey Fungi-Fighter
Ortho RosePride Funginex
Ortho RosePride Orthenex
Safer Flower, Fruit & Vegetable Garden Fungicide
triadimefon (Bayleton, Strike)
Spectracide IMMUNOX

Pruning now will make them bush out and look much better.

    Bookmark   May 6, 2010 at 11:02AM
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Ok I won't do the watering like I was. They haven't been mulched since they were put in last Sept. Do you recommend any certain mulch that's better for them than others? I wondered about which type of fertilizer to use on them since there are so many varieties so I will go with what you have listed. Do you think I should go ahead and use the fungicide now to help prevent? Also by pruning can I just cut the tops and sides minimal or do you recommend the pinch method. I have never had azaleas so don't know to handle them best. Thanks so much for your help.

    Bookmark   May 6, 2010 at 12:19PM
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rhodyman(SE PA, USDA Z6)

Pinching is good for keeping plants at a certain height. Pruning is better if you want to reduce the height.

If you spray, spray now to prevent the new foliage from getting infected. But it is even better to also remove all infected leaves and destroy them (put them in with the trash that is hauled away).

If it were me, I would ignore the powdery mildew or whatever it, since it affects such a small number of leaves. I would remove and destroy the infected leaves and let it go. Old leaves that are being shed tend to look like that also.

    Bookmark   May 6, 2010 at 4:43PM
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