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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Brown Leaf Tips
Q. I have been fighting this disease on my huge Green Hornet for years. I’ve sprayed with many things, to no avail. Possibly I didn’t follow up with a second spraying?A. That looks like anthracnose on the Epidendrum/Prosthecea. Those fine dots on the brown leaf tips are the sporing bodies that spread the disease. Cut away the damaged leaf tips. You might consider spraying monthly with something containing thiophanate methyl until you don't see the disease anymore. More air movement and less leaf wetness also help prevent fungal infections. (May-26)
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Time to Repot
Q. Is this the right time to divide and/or repot this Cattleya?A. Yes, repot/divide it now. You can cut the new growths off and repot it into a new pot, probably the newest five pseudobulbs can be removed,but be gentle with those new roots. Then decide what you want to do with the older part of the plant. If the old mix is still okay, you may wait for a new growth to sprout from the back bulbs, but it looks like it's trying to escape from the pot so the mix may be degraded or have become salty. (May-26)
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Black Spotting on Bifoliate
Q. This bifoliate has had black spotting since it was fairly young. It sort of looks like a sooty mold that doesn’t wipe off. Treating it with mild fungicide had no effect, but since the plant was otherwise OK and flowered nicely (no color break), I've kept it. Now, however, although the last two sets of leaves are clear, diffuse spotting is on all the other leaves. I can't ignore whatever is wrong with it. Should I invest in a virus test, treat it, or just toss it?A. I love the bifoliates, but sure hate to see that black splotchiness. It is suggestive of Cymbidium Mosaic Virus although the diffuse spotting is also suggestive of a fungal infection, particularly with the fine dotting on the leaf undersides. There is really only one way to rule out virus and that is to test it. So if you test it and it's positive, you probably toss it. If you test it and it's negative, you have a fungal problem to deal with, which would require you to cut away a clean section of the plant, treat it with a systemic fungicide and then get it growing again. (May-26)