Orchid Culture Questions and Answers
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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 Marks on Leaf Edges
Brown Marks on Leaf Edges
Brown Marks on Leaf Edges
 

Brown Marks on Leaf Edges

Q. I have had Otaara Island Flare for ten years. I noticed these brown marks on the edges of the top leaves. It seems to also be on the underside of the older leaves but not so much on the younger leaves. On the underside they seem to be more widespread. It does not feel pitted but it may just be very shallow and not readily detectable. The new growth is clean, the flowers look good and it is growing well.  

A. I don't think it's viral or bacterial, so that leaves fungal, probably one of the leaf spotting fungi. The problem with a fungus is that once it's inside the plant, it is beyond the reach of most fungicides so even if you wanted to spray, it wouldn't really help. So here's the choice, if the plant is strong enough, cut off the infected tissue and discard it, and then pamper what is left, if you want to you can spray with something to protect what's remaining. If the plant isn't strong enough to cut away the obviously diseased tissue, then just move it away from your other stuff and let it do its thing. This may be caused by Guignardia/Phyllosticta or a different fungus that we haven't previously associated with our orchids. Carole updated us "I think I can cut away the affected leaves and bulbs and still save the plant. I will cut it up and spray fungicide."   (Dec-18)


Tiny Spotting on Leaf Undersides

 

Tiny Spotting on Leaf Undersides

Q. Do you have any idea as to the problem with this Den. aggregatum? It was doing beautifully until this year. The plant lives outside under an oak tree and receives minimal morning sun.  

A. The spotting on leaf undersides is likely fungal, possibly Cercospora dendrobii. More air movement would help. We've had lots of rain here this year, so the excess leaf wetness can create a conducive environment for fungal growth. You can remove severely affected leaves and spray with a fungicide like Daconil, but more air is the long term solution. Here's an interesting post from an Aussie blogger that recommends spraying lime water for Cercospora dendrobii.   (Dec-18)


New Bag Babies
New Bag Babies
 

New Bag Babies

Q. Yesterday I picked up 2 bag babies. I found this black patch on the Brassavola when I got it home. Is it black rot? What would you suggest I do? I also notice a couple of brown patches on the pseudobulbs of the Schomburgkia orchid. I did not realize how large this plant can grow until I came home and googled it. I also read about ants living in this plant. Does it mean that ants are a given with this plant? I donít want ants to infest my house / growing area because they are attracted to it?  

A. Cut off the one leaf on the Brassavola, looks like maybe it got sunburned while being tortured in the store. It looks healthy otherwise. The Schomburgkia looks healthy too, don't know what the brown patches are but as long as they are not soft, they'll be fine. In nature, ants have a symbiotic relationship with the orchid, but they won't infest the plant in the house. No worries, the plants are healthy and should do fine for you.   (Dec-18)


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