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Black rot on Pleurothallids

Discussion in 'Issues, Disease and Pests' started by Raven, Nov 1, 2017.

  1. Raven

    Raven Well-Known Member

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    Just found out that my Masdevallia datura and a few others imported last month are infected with black rot (based on symptoms). I know that these are very finicky pathogens, and I won't be able to kill them with normal fungicides. What do you guys use to treat pleurothallids and other humidity-loving orchids with black rot? What can be purchased on the American market and is NOT super expensive?
    Thanks!

    P.S. I've been growing orchids for several years, and have never had any black rot before. I'm a little worried!
     
  2. Chuck-NH

    Chuck-NH Well-Known Member

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    Hi Raven,

    I always expect some black rot (generally Phytophora) when importing small cool growing Pleurothallids. They generally don't like to be boxed up and travel through warm places before they get to us. Generally, I do a quick soak with dilute Disinfectant (Zerotol, Physan). If I suspect any infection, I quicky hit with Subdue Max which generally stops the rot in its tracks after one treatment. Probably expensive, but it really works. I've also used Daconil and Captan with moderate success in the past.
     
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  3. Raven

    Raven Well-Known Member

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    Thanks, Chuck. I found some info saying that Truban 25, and Aliette WDG can also kill black rot. Have you heard anything about them? They are like twice cheaper comparing to Subdue Max.
     
  4. Chuck-NH

    Chuck-NH Well-Known Member

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    I haven't used either one, but note that the AOS website indicated Truban for early stage infections but pointed to Aliette or Subdue for advanced stage.
     
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  5. Ray

    Ray Orchid Iconoclast Supporting Member

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    After the folks at Inocucor gave me a sample of their "Garden Solution" biological product, and I started using it on a regular basis (1.5 oz/gal, once a month), the incidence of rots has plummeted to zero for me, even with overhead watering. It is not sold as a curative, as that would open up all sorts of onerous registration issues, but at double that concentration, I stopped erwinia cold in a phalaenopsis in a matter of a few days.

    That's what convinced me to sell the stuff. It is available via Amazon, but shipping is included in the price if it comes from me directly.
     
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  6. Chuck-NH

    Chuck-NH Well-Known Member

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    Hi Ray...I think I'm going to try some. My wife had used something similar in her Nursery for establishing plugs and seedlings and it seemed successful. And...It's a pain to suit up when spraying the highly toxic stuff. If I can incorporate something organic and of low toxicity, it's worth a try. Save the toxic option for last defense.
     
  7. Raven

    Raven Well-Known Member

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    Chuck,
    I think I'm gonna try Aliette then, since it is twice cheaper than Sudue!
    Do you think other Trichoderma products could give similar results? I always treat deflasked seedlings with RootShiled and I have very low mortality rates even for fussiest species.
     
  8. Jgrimm1055

    Jgrimm1055 Jonathan loves Masdevallias!

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    Raven would you mind posting some pictures? I've been growing Pleurothallids for a few years. I'm still a noobie when it comes to fungus, bacteria and pests. I would love to see some reference so I know what to look for.
     
  9. Ray

    Ray Orchid Iconoclast Supporting Member

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    Certainly trichoderma is effective, but is only one species of "critter", so isn't as broad-spectrum as the Inocucor product, with more than a dozen.
     
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  10. Raven

    Raven Well-Known Member

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    I cut all the diseased parts off last Thursday so there is nothing much to "show". I'll make sure to take pictures when they develope new symptoms. It mostly affects younger leaves, the older ones seem to be pretty resistant. I think this is some sort of Pythium. I tried systemic fungicides and bactericides without success, this is how assumed it should be an oomycete (Phytophthora or Pythium).
     
  11. Raven

    Raven Well-Known Member

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    Spraying with cinnamon and rootshield didn't help much :(
    Can somebody confirm that this is a Black Rot, so we can use this pictures for reference, and so I'm convinced enough to spend $ Black rot 2.jpg Black rot 1.jpg 180 on fungicides LOL
     
  12. naoki

    naoki Well-Known Member

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    I'm not sure, but it looks like a physiological stress.
     
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  13. Chuck-NH

    Chuck-NH Well-Known Member

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    Have you taken a look at the roots? When I see something like that I do often find dead roots with fungus. Whether the fungus is the primary cause of the root death or just an opportunist that moved in is sometimes hard to tell unless you can find/remember other factors that may have been involved. Overwatering, too warm at night, stale media...etc.
     
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  14. Raven

    Raven Well-Known Member

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    Other masdies and draculas are fine, the only ones that sick are datura, exquisita, and decumana. Always thought of them as of more intermediate growers. But I got my decumana from J&L already rootless, while the other two are slowly dying.

    Chuck, the media is new, they are in tree fern, so no overwatering, the roots are mostly dead, but without any signs of mycelial growth.
     
  15. Marni

    Marni Well-Known Member Staff Member Supporting Member

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    If it doesn't have any roots, it is in too big a pot. Without roots pulling the water up, it won't approach dryness between waterings. I grow Masdevallia decumana and exquisita cool. I have grown datura both cool and intermediate, but prefer it in intermediate. They all do well mounted.
     
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  16. Raven

    Raven Well-Known Member

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    Marni, thanks for your input.
    Does it look to you like physiological stress or some sort of infection, based on my pictures?
     
  17. Ray

    Ray Orchid Iconoclast Supporting Member

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    The answer to that is probably "both." I have found that, for the most part, plants don't get fungal or bacterial diseases unless they are put under some sort of stress, with under-watering, root loss due to suffocation, out-of-bounds temperatures being some of the "biggies".
     
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  18. Chuck-NH

    Chuck-NH Well-Known Member

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    As I implied earlier, I would also say "probably both" as Ray did. I see similar looking plants as yours that have been recently imported, typically Masdevallia. Where they have new growth as yours does, they typically survive. I find that putting the plant (talking Masdevallias) in a small net pot with only New Zealand Sphagnum and keeping "slightly" moist will greatly improve chances of survival. Once well rooted, I then repot into the mix of choice or mount. For plants in bad shape, I have also used a systemic fungicide with success, but am going to start experimenting with the Inocucor.
     
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