Rhododendrons: disease id

Discussion in 'Ericaceae (rhododendrons, arbutus, etc.)' started by begreen, Mar 23, 2005.

  1. begreen

    begreen Member

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    my first post, thanks for having this great site
    a couple of examples of rhodos with problems i have come across- one appears to be perhaps a fungal disease, perhaps spores along the leaf edge and on stem
     

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  2. Newt

    Newt Well-Known Member 10 Years

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  3. Ron B

    Ron B Paragon of Plants 10 Years

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    The plant in the middle shot is an indumented rhododendron, the fuzz near the edge is its own natural hairs.
     
  4. GRSJr

    GRSJr Active Member 10 Years

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    From the recommended site. These only seem to slow the destruction here in North Carolina.

    I have seen a miraculous recovery of 'Chionoides' when I applied "Messenger". The root rot had already destroyed several branches and the plant was well on the way to death.

    After only one application of "Messenger" it revived. Now, after 3 years and 2 more applications, it looks perfectly healthy.

    Unfortunately, "Messenger" is packaged for farm use and is expensive because the smallest pack will do acres of plant. I wish we could get Eden Bioscience to package it for garden use.

    I've also applied it to my other Rhododendrons. There is some improvement in 2 'Boule de Niege', but 2 died from the root rot. 'Scintellation' is under siege this year, so we'll see if more "Messenger" helps.

    All the others seem to be healhy so I can't tell if "Messenger" helped them or not.
     
  5. fourd

    fourd Active Member 10 Years

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    I believe the fungus you are seeing, all pictures is form of powdery Mildew. It can take on a diferent looks depending on the plant. It is treatable via a prevenitive fungicide but the leaves that have it will likely have it till they drop, hence dead leaves should be discarded to discourage the spread. Most fungus in rhododendrons are the result of some other condition unfavorable to rhododendron. For example, overly wet spring/fall, overwatering, clay soils, high PH, scald or winburn ... all can alow fungus to set in, hence fungi are usually a secondary infection.
     
  6. GRSJr

    GRSJr Active Member 10 Years

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    Sorry, I responded to the wrong thread.
     
    Last edited: Aug 3, 2005
  7. Ron B

    Ron B Paragon of Plants 10 Years

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    I don't see anything I would call mildew in any of these shots. Being a Yak it shouldn't be having much problem with mildew. It DOES look like the plant is getting too much exposure, too much fertilizer, or having some other problem of that nature that is causing it to become scorched. Dousing it with additional harsh agents (fungicides) is unlikely to make life better for it. At any rate, always find out exactly what a plant's problem is before reaching for a spray bottle.
     
  8. mr.shep

    mr.shep Well-Known Member 10 Years

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    What kinds of fertilizers are being used for these
    Rhododendrons? How much water is being applied
    and how often are you watering? What kind of mulch
    or amended soil are you using?

    I am seeing the effects of salt burn, sunburn and
    some leaf chlorosis in the last photo. I agree with
    Ron, I am not seeing powdery mildew (grayish white
    colored raised patches or splotches) on the leaves.
    The second photo sure does appear to be indumentum.

    Jim
     
  9. fourd

    fourd Active Member 10 Years

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    Ron's advice is rock solid! While we may disagree as to whether fungi is present, fungi is more or less of a symptom of a problem so you should be looking at finding the root problem.
     
  10. fourd

    fourd Active Member 10 Years

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    BTW, Rhododendrons with powdery mildew don't usually display the whitish grey powdery like spores as found with powdery mildew in other plants. Yes, if you catch it at the right time you may see some white, grey, or yellow spores, but you certainly can't rule it out based on absence of powder. And to complicate it further, it's appearance varries with cultivar/species as well as local.

    http://gardening.wsu.edu/column/06-11-00.htm

    The above article touches on it by discussing Microsphaera azalea, probably because that one is prevelant in Washington, but In other locals, there is another Microsphaera ssp as well as several other fungi in rhodies that are refered to as powdery mildew.
     
  11. douglas

    douglas Active Member 10 Years

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    Hi
    Might want to the check the under side of the middle pic for white fly. Had several in the fraser valley that were affected.

    Regards Doug
     

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