Cattleya new lead amputation - black rot

[kbishkin]

Hi there!

I'm wondering if anyone can give me some advise on this trauma patient.

A few days ago I noticed black rot developing on a new lead. I think what happened was, I was trying to water the aerial roots you see in the picture and got water in the new lead.

There was a spot on a new leaf and an interior leaf was black. It looked like the interior leaf rot went pretty far into the psudobulb so, not wanting it to spread to the rest of the plant, I cut it off just under the rot. It turned out the rot went about an inch into the p-bulb.

I applied physan to the cut with a q-tip and let it dry out in the sun. (I'm out of cinnamon). The wound looks black and nasty but I would imagine that is just dead tissue. I'm trying to keep the circulation up and the new lead totally dry.

My question is: what now? Can it survive the surgery? I've probably removed the "stem cells" where the new growth originates just under the leaves. So I would imagine that the p-bulb won't grow to maturity. I was wondering if the immature p-bulb - which just started putting out new roots - might live. Or is it a lost cause? If so, what should I do?

Here is my culture, since people tend to ask:

Temp.

Day:70-85 f
Night:65-75 f

Humidity: No idea. It's low

Lighting: south facing window

Air movement: Ceiling fan on high

Potting: bark and a lot of inert material. I put some sphag on the aerial roots to increase humidity around the plant.

Thank you!

p.s. I've included a picture of the flowers it put out in April. This lady is my favorite so I hope it's ok!

Katie

[tucker85]

I grow my orchids outdoors in Florida. During the rainy season I always lose a few psuedobulbs to black rot. Generally the plant will survive and whats left of the psuedobulb will stay green. Occasionally the rot will continue down into the rest of the plant and kill it. The spores for black rot are almost always around in orchid collections just waiting for water to sit in the orchids too long and get it growing. Just be certain that you cut off below all the black area. New leads will form somewhere on the plant to keep it growing. Occasional spraying with Physan 20 or a stronger fungicide can help but there's always the chance of it striking an orchid.

[Leafmite]

I found isopropyl alcohol stops black rot. I saved a few leads this way, some on my cattleyas and one on my psychopsis. I used cotton balls or cotton swabs and wiped it until the cotton was no longer discolored. I then treated twice a day for a week. The seedling cattleyas I didn't catch in time succumbed as it did spread. The treated ones recovered (although the worst mature cattleya will probably skip blooming until autumn). I read that adding calcium is believed to help prevent this from happening so I have been using crushed oyster shell. So far, the new growths are healthy. Good luck!

[kbishkin]

Thanks guys. Have either of you ever seen a new lead continue to grow after it's been chopped? On other genera, I've seen damaged new growths come back. But I'm not sure about cattleyas.

[Leafmite]

It likely depends how much you cut. If the roots are still fine and support what is left, a new growth should eventually begin off of it. Sometimes the 'mother' growth will send out a second new growth if it is too far gone. And, if any of the new leaf remains, it will continue to grow. Just make certain the black rot doesn't spread.

[BettyE]

Just for information: I have in the past had to deal severely with black rot/mildew, on new growth of cattleyas. What I did was to cut off below the rot with a sterile knife, then spray with alcohol. Then I immediately dusted the cut with horicultural sulphur. After yrs. of experimenting, I have found this method to work ALL the time! The alcohol kills the bacteria, & gives a moist place for the sulphur to stick to. The sulphur kills any bacteria, also. Needless to say, I cried when I had to cut new growths on three cattleyas, but it had to be done to save the rest of the orchid(s) This Winter I will have flowers on all three, & will make sure that my humidity stays at or below 50% and NO water gets into the new growth... These are real experiments on my own orchids... BettyE