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Re: [AZ] Damaged Azaleas, searching for reason

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  • Joe Schild
    This is from Steve Henning as a cc. Joe Schild-Hixson, TN It looks like: 1) some chlorosis, yellowing leaves with green veins. 2) some lace bug, fading
    Message 1 of 6 , Sep 10, 2012
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      This is from Steve Henning as a cc.
       
      Joe Schild-Hixson, TN
       
      It looks like:
      1)  some chlorosis, yellowing leaves with green veins.
      2)  some lace bug, fading speckled leaves.
      3)  some drought or chemical burn, brown tips.

      1) Yellowing of a leaf between dark green veins is called chlorosis and is usually caused by an iron deficiency. Many conditions can be responsible for an iron deficiency. Poor drainage, planting too deeply, heavy soil with poor aeration, insect or fungus damage in the root zone and lack of moi sture all induce chlorosis. After these conditions are eliminated as possible causes, soil testing is in order. Chlorosis can be caused by malnutrition caused by alkalinity of the soil, potassium deficiency, calcium deficiency, iron deficiency, magnesium deficiency or too much phosphorus in the soil. Iron is most readily available in acidic soils between pH 4.5-6.0. When the soil pH is above 6.5, iron may be present in adequate amounts, but is in an unusable form, due to an excessive amount of calcium carbonate. This can occur when plants are placed too close to cement foundations or walkways. Soil amendments that acidify the soil, such as iron sulfate or sulfur, are the best long term solution. For a quick but only temporary improvement in the appearance of the foliage, ferrous sulfate can be dissolved in water (1 ounce in 2 gallons of water) and sprinkled on the foliage. Some garden centers sell chelated iron that provides the same results. Follow the label recommendations for mixing and applying chelated iron. A combination of acidification with sulfur and iron supplements such as chelated iron or iron sulfate will usually treat this problem. Chlorosis caused by magnesium deficiency is initially the same as iron, but progresses to form reddish purple blotches and marginal leaf necrosis (browning of leaf edges). Epsom salts are a good source of supplemental magnesium. Chlorosis can also be caused by nitrogen toxicity (usually caused by nitrate fertilizers) or other conditions that damage the roots such as root rot, severe cutting of the roots, root weevils or root death caused by extreme amounts of fertilizer. 

      2) Whitish specks on th e upper surface of leaves and dark spots varnish-like on the bottom are symptoms of Rhododendron Lace Bugs, Stephanitis rhododendri, and Azalea Lace Bugs, Stephanitis pyrioides, small insects with transparent wings on under-surface of leaves. This insect hatches early in spring as the new foliage begins to mature and its numbers may build to damaging levels with successive generations. Lace bugs reach their peak in late summer and do their worst in sunny, exposed sites. Spiders are important predators of lace bugs and since they shy away from sunny, hot places, plant your azaleas where there is some shade. Insecticidal soap, horticultural oil, or a systemic insecticide may spare your azaleas the damage if applied in spring when the first hatchlings are noticed. Care must be taken to spray the lower surfaces of the leaves where the lace bugs live. Moving a plant to an area with more shade may alleviat e the problem. Lace bugs are more prevalent on certain varieties.

      Steve Henning, Zone 6, Reading, PA  USA
      ----- Original Message -----
      From: Gibson
      Sent: Sunday, September 09, 2012 7:33 AM
      Subject: [AZ] Damaged Azaleas, searching for reason

       

      [this is from the ASK US page, so please send me a CC]
      Hi,

      I'm writing cause almost all my azaleas bushes are damaged in a similar way, probably at differet stages. I can't understand the reason, sun bursts, too much water, needs of fertilization...can you help me? I post some image.

    • Gibson
      Thanks to everyone, sorry for delay but I initially wrote with azaleas.orgdirections but I wasn t receiving answers. Unfortunately I can t move my azaleas
      Message 2 of 6 , Sep 11, 2012
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        Thanks to everyone, sorry for delay but I initially wrote with azaleas.org directions but I wasn't receiving answers.
        Unfortunately I can't move my azaleas cause are part of a japanese garden but I think that the lack of iron can be due to artificial irrigation. I'll try to follow your suggestions hoping to recover the plants before winter.
        You think that the near growing hedera can in some way hurt azaleas? I keep it outside the root area but maybe...
        Thanks again in advance.
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