What is wrong?

Discussion in 'HortForum' started by Carol Noel, Dec 18, 2003.

  1. Carol Noel

    Carol Noel Member

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    On the East side of the Big Island of Hawaii...nea
    Something is very definitely Not Right with this plant....and I cannot find the solution...hoping some one here has some ideas.

    The plant is a Hoya...H. naumanii to be exact. All of the cuttings taken from the original cutting sent to me from Australia are showing the same distorted and discoloured leaves. I have sent leaves to the Plant Pathology Lab at the University of Hawaii at Hilo and Manoa and the report came back negative for Tobacco Mosaic Virus (my first thought) and no sign of insect damage. I have a greenhouse full of Hoya...over 200 plants...and this is the only one affected! I water and fertilize all my hoya the same (basically), have used no pesticides.

    I am stumped.

    Thanks in advance.


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  2. T. Shane Freeman

    T. Shane Freeman Active Member

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    Brandon, Manitoba, Canada
    I am not particularily familiar with Hoya spp. but I wonder if you are dealing with a form of mineral deficiency.

    You stated that all cuttings taken from the same plant sent from Australia are illustrating similar characteristics, yet none of the currently growing Hoya's are. Thus it doesn't take a rocket scientist to realize that you are dealing with a host specific problem!

    If you were dealing with a fungal, bacterial, or viral pathogen, I would think that you would have started to notice transmission to your already healthy stock. In addition, all affected media were cuttings, therefore, must have been planted in your own pasturized/steralized media. This would omit the chance that the media had been contaminated with a toxic agent, for if it had, the other plants would be showing similar characteristics. So what is your media deficient in.....................what is the plant looking for?

    The omission of any one of the seventeen essential elements needed for a cultivated species, like your Hoya, to adequately survive will result in varying physical symptoms.

    Just in case I way off, I will cut to the chase...........

    My interpretation of your supplied pictures is that the newer or bud leaves are affected and that the symptoms are more localized (as opposed to the older or lower leaves of the plant being most affected with effects localized or generalized). Your picture on the right seems to portray the deficient leaves being located near the apical (tip) end of one cutting.

    In addition, the terminal bud has NOT died, but yet remained alive. Wilting and chlorosis of younger or bud leaves with little or no necrosis (dead tissue) is evident. The veins are light green in color. This leads me to think that your plant is deficient in one of the following four elements: Copper, Manganese, Sulfer, or Iron.

    For plants deficient in Copper, young leaves are permantly wilted without spotting or marked chlorosis....................your plant my be wilting, but it definitely has chlorotic characteristics.......................REJECTED!

    The remaining three element can all have minor wilting, but chlorosis is present with or without spots of dead tissue scattered over leaf.

    Managanese deficient plants have spots of dead tissue scattered over the leaf...........................which from what I can tell, your plant does not...................REJECTED!

    Sulfur and Iron both commonly illustrate little to no dead spotting, chlorosis of tissue, and green veins (darker than chlorotic tissue).

    The young leaves on sulfur deficient plants have veins slightly darker than surrounding chlorotic tissue..............................POSSIBILITY!

    The young leaves on iron deficient plants are chlorotic, the principal veins green, but have short and slender stalks.............................YOU BE THE JUDGE OF THAT!

    But seeing how these final two element are micronutrients or otherwise known as trace elements, they could have potentially caried over from their Australian environment.

    To further my arguement, Salisbury and Ross state that "....ecause enough sulfate is present in most soils, sulfur-deficient plants are fairly uncommon. Nevertheless, they have been observed in several parts of Australia, some regions of Scandinavia... (131)" Therefore, if you have several plants that are showing the same characteristics, do some exparimenting. Apply some chelated iron to one plant and some chelated sulfur to another. See if your problem improves.

    My money is on the sulfur!

    T. Shane Freeman

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