Orchid Culture - Questions & Answers from This Month
by Sue Bottom, from the St. Augustine Orchid Society Newsletter. Email us with any orchid question. If we can't answer it, we'll find someone who can! Send photographs too!
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Habenaria Flowers Have Browned
Q. I understand what I’m looking/waiting for with the leaves on this habenaria. Can I go ahead and cut the bloom now that it’s turned brown?A. You can cut off the bloom. You can start watering a little less frequently, the tuberoids are still forming below the surface. When the leaves start to brown, reduce watering even more and stop completely when all the leaves have browned. When the top growth can be removed with a gentle tug, you can unpot the tuberoids for winter storage either in an empty clay pot or plastic bag. (Dec-24)
Necrotic Lesions at Cattleya Leaf Base
Q. My cattleya plant shows necrotic discoloration/lesions at the leaf bottom of the youngest growth. The plant grows vigorously and no other growth shows any spotting. The lesions are small (2-6mm) dark brown vertical/striations and have an outer lighter edge. The plant has been quarantined for about two months and the size, color or texture has not changed since. The leaf also shows a slight deformity (waved edge), where the top left striation is. I assume it may be CymMV, but am also hoping that there is a chance that this is an old bacterial infection only. My orchids are treated with Banrot or Zerotol and Dithane every 6-8 weeks depending on humidity levels and rainfall.A. If I had to guess, I would say that as that leaf was forming, there was some water pocketing at the base that caused a bacterial infection. You can see where it might have been deformed slightly as it was growing. You never know til you test it, but virus would not be my first suspicion. (Dec-24)
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Phal Loses Its Leaves
Q. I have been dealing with a lesion on the phalaenopsis leaves problem for a couple of years, but am not sure what is causing it? I have cut off leaves in the past. I had one lose all its leaves, but I kept caring for it and now it is growing new leaves. Any help you can offer would be appreciated.A. My guess would be you had a bacterial soft rot happening, particularly if the lesion was soft and water filled, enlarging rapidly. If it gets to the crown of the plant, the growing tip is lost and its only hope for survival is throwing a basal keiki, as happened on the pictured phal. The best precaution is to keep the phal leaves dry. (Dec-24)
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Black Scar on Pseuodbulbs
Q. This Cattleya’s last two growth are a bit deformed. It started with very adherent dark sheaths. When the leaves started to curve, I removed the sheaths to find these dark Dry patches on the back of the leaves. The leaves continue to grow but are a bit curved. I assume this is because these dark patches are like a scar which does not have growth potential. I would appreciate your advice.A. I think I can see the problem you are having. If you look at the newest growth, you can see a pocket is formed by the sheath surrounding the pseudobulb. Water inevitably gets trapped in there, whether from day/night condensation or from watering. You develop a bacterial infection in there that causes the black discoloration and distortion. You can see the black streaks moving up the leaf from the bacterial infection that started in the pocket. When I see those pockets, I will run my finger down through it to slit the sheath, so water can drain freely. You can use a razor blade or plant tag or whatever works for you, but once the water drains freely, you won't continue to have the problem.I don't think the infection is active now, so no worries on that front. (Nov-24)
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Is This a Virus Spreading?
Q. At first I thought this was a light intensity issue, or maybe just purple spotting on the leaves because the flowers are so heavily spotted, but then it turned into lesions and I started to see a similar thing on other catts. I did read the article on edema, but given the time of year, and the fact that it seems to be moving from plant to plant has me thinking virus.A. My first impression is that you have mites on the orchids, have you inspected with a loupe or magnifier to check for mites? I don't usually see mites on cattleyas, but I would guess the young emerging leaves are susceptible before the waxy cuticle forms. I have heard from other growers that mites are a problem on their cattleyas. Perhaps my catasetums act like the canary in the coal mine so the mites go after catasetums rather than cattleyas. You'll need to spray with a miticide like Avid, probably 3 successive treatments a week apart. Good luck! (Nov-24)
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Sunken Brown Spots on Cattleya Leaf
Q. These sunken brown spots are on new and old growths. I've sprayed twice with Banrot and Subdue.A. That looks like a bacterial infection, most likely Pseudomonas which spreads pretty quickly on the new growths, more slowly on the older growths. You'll need to spray with a bactericide, fungicides won't touch a bacterial infection. Copper is the old go-to favorite, but best not to use in on the thin leaved orchids, seedlings and dendrobiums. You can spray liquid copper, Kocide or other formulations on cattleyas and phals, and you can also use it to nuke under benches to control snails and slugs. (Nov-24)