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kris2001

Rhodies brown-curly leaf fungus-spray frequency?

kris2001
16 years ago

I sprayed Mancozeb (manzate) on my roses as a fungicide. I sprayed it on the Rhodies too. Will it work for Rhodies too? I heard its powerful? I am also spraying bayer advanced disease control on my roses. Can I use it for rhodys? If so what is the frequency of spraying for rhodys?

Also I remove old brown leaves , is it ok?

The black tips in dead flowers-are they seeds-is it easy to grow them from seeds?

Has anyone used 'messenger' for rhodies?

Thanks guys!

Comments (5)

  • rhodyman
    16 years ago

    Why spray the rhodies? Do you have any problems?

    The sprays are poisons and should only be used where needed and not used indiscriminately on everything.

    I never spray my rhodies. I let nature take its course. It usually solves most problems. I do remove diseased material. Often spraying for one problem will cause other problems. The total interaction needs to be known.

    The major toxicological concern from exposure to mancozeb is the hazard to the human thyroid from presence of ethylenethiourea (ETU), a contaminant, degradation product, and metabolite present in mancozeb and other EDC products. ETU is an acknowledged goitrogen, teratogen and oncogen.

    For many of us, this past winter our plants took a beating with the very unusual winters some of us had with warm weather followed by late freezes. They have what is more typical of drought damage but in this case was caused by the warm weather followed by late freezes. It causes Botryosphaeria dothidea which causes leaves to turn dull green and then brown and roll and droop. Cankers form on branches which may girdle the branch.

    This is the most common disease of rhododendrons in the landscape. A typical symptom of this fungal disease is scattered dying branches on an otherwise healthy plant. Leaves on infected stems turn brown, then droop and roll inward. These leaves often lay flat against the stem and will remain attached. The pathogen can infect all ages of stem tissue through wounds, pruning cuts, and leaf scars. Heat, drought stress, and winter injury can increase disease incidence. Cankers on branches can gradually grow through the wood until the stem becomes girdled. Diseased wood is reddish brown in appearance. Discolored wood viewed in longitudinal cross section often forms a wedge that points toward the center of the stem, and the pith may be darker brown than the surrounding wood.

    Sanitation and applying a fungicide such as metalaxyl (Subdue) after pruning my provide some control. Plants should be grown in partial shade, with mulch and kept well watered during dry periods. All dying branches should be promptly pruned out in dry weather and all discolored wood should be removed. Plants should also be protected from rough treatment during maintenance activities to prevent unnecessary wounds.

  • kris2001
    Original Author
    16 years ago

    Yes, they had the brown leaves curling in and falling. Must be the fungus right? Also are rhodys easy to grow from seed, I collected seeds from old flowers, seeds look like match stick. is that the seed?

  • jean001
    16 years ago

    You wrote:
    "Yes, they had the brown leaves curling in and falling. Must be the fungus right?"

    Maybe. Maybe not. We need a more detailed description. Can you post a photo?

  • rhodyman
    16 years ago

    It is probably winter damage and an opportunistic fungus took advantage of it. The key is to remove the disease leaves and stems and make sure the plant is otherwise healthy. This fungus doesn't attack healthy parts of the plant. Most people never spray rhododendrons for fungus. It can be done, especially in nurseries, but this fungus is everywhere waiting for a damaged branch to attack.

  • morz8 - Washington Coast
    16 years ago

    kris, you may just be seeing winter damage alone - and with or without a secondary fungal infection your best action may be to just remove (sharp pruners) the damage. It's better to never use a chemical without an accurate ID of your insect or disease...If you take an example leaf/stem/twig to a reputable nursery (not a box store) or to your county extension agent, or post a photo here, you may get a more complete answer.

    As for the seeds, visible seed capsules form on rhododendrons and those ripen in late summer. The seed itself is produced in large quantities and is tiny, almost like dust. But keep in mind that setting seed takes a great deal of plant energy that would otherwise be directed to next Springs flower production. If you don't deadhead you may have seed, but far fewer flowers next year.

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