Sobralia Andreae with black leaves - Orchid Board

chiquib313 · #1 06-29-2012, 10:01 AM

I recently acquired a Colombian Sobralia Andreae at the Redlands Orchids Festival and it has developed large black blotches on the leaves that eventually turn all black and fall off. What is the best treatment method to contain this and could this infect the other orchids in my collection? I was informed I should use a "systemic fungicide" but not sure which one would be most appropriate for this this plant. I have cut off all black leaves for now and sprayed with Physan 20 and separated the plant from the rest of the orchids just to make sure it does not spread. Attached are some photos. Anyone have any suggestions?

james mickelso · #2 06-29-2012, 10:49 PM

It could be a fungus but I suspect that this orchid is waaaayyyyyy too wet. I would let it dry out and hope enough leaves and roots are left to keep it going. I would isolate it from your other collection just in case it is fungal. It may be black leaf. I just lost an acquired blooming size c. kodama "chocolate drop" from a respected dealer that died within days of it's appearance. I cut and cauterized with cinnamon well ahead of the infection but it kept growing until the entire plant was black.

Zoi2 · #3 06-30-2012, 07:10 PM

What kind of sun is the plant getting? It looks like severe burn to me.
Joann

chiquib313 · #4 07-01-2012, 09:57 AM

The plant is outdoors, east exposure, and only receives morning sun. It is planted in a mix of good draining potting soil and bark mix to aid drainage. I hope you are right and it is only sunburn. I only purchased this plant a month ago and the vendor said that it was caused by the stress of travel (Colombia to Miami) and the repotting & transplanting. I have sprayed it with Physan 20 and I am planning to treat with Cleary's just in case it is a fungal infection unless anyone has any other recommendations.

stefpix · #5 07-01-2012, 10:22 AM

I would cut all the black off including some adjacent green areas. Just in case...

chiquib313 · #6 07-01-2012, 12:06 PM

Thanks, Stefano. Only the leaves seem to be affected. I have already cut off all the black leaves and am carefully watching the new leaves to see if they turn black.

stefpix · #7 07-01-2012, 02:53 PM

Yeah, that could probably tell if it is fungus or sunburn... Although I fear it may not be sunburn as in that case there would be round irregular spots and not such a clear margin. it looks something systemic that affects the whole leaf. I could be wrong. Or I wonder if it could be a heat stroke instead, maybe it had been left in a parked truck in the sun.

chiquib313 · #8 07-01-2012, 04:13 PM

I'll never know if it was left in the sun and burned prior to my purchasing it. But just in case and to play safe, I ordered some Cleary's and will begin to apply as soon as I receive it in the next couple of days and hope that does the trick. Thanks for your input.

stefpix · #9 07-01-2012, 04:18 PM

I did not mean in the sun but in the heat - different. maybe it was left in a hot car..

james mickelso · #10 07-01-2012, 05:06 PM

I don't know but it just looks like my zygopetalums and lycaste when they get too much water. Sobralias like water but don't like to sit in it. They do not like water during their winter. They also like a mix that incorporates a lot of organic matter and bark but drains well. What do your roots look like? How damp is the potting mix it is in? I know sobralias grow in the hot tropics where it gets wet season (summer)and dry season Fall /Winter). They can take full sun. The brighter the light the larger the flowers.