Help black rot?
 

I just took the sheath off this healthy mature growth. What should I do?

First, take a very sharp blade - new razor blade, very sharp knife, very sharp scissors - and sterilize it with 70% isopropyl rubbing alcohol. Let it dry. Cut off that growth with just one cut as far below the rot as you easily can. Sterilize the blade again, or throw it away.

Second - dust the cut surface with a small amount of powdered cinnamon. Try not to get the cinnamon on the roots.

Third - put it in a low-humidity but well-lit part of your house for a few days so the cut surface dries. Then put it back in your growing area.

I'm surprised that happened because the plant looks otherwise healthy, with new root growth. What are your day/night temperatures where it was growing? Humidity? Did it get a lot of direct sun?

It grew outside in my shade house all summer so it got good light. In early September it came into the grow space under lights in my house. It's usually 65 to 75 percent humidity and around 75 during the day and 65 at night. The last new growth it developed a black spot as well so I chopped it off. I would like to prevent this as I just lost a bifoliate to black rot...the whole thing rotted in less than two weeks even with physan treatments.

I see ..... you took the sheath off and found the rotting activity. When you water, does the water get into the region between the sheath and the actual bulb?

Maybe water got trapped and some bacterial activity started it off.

Orchids definitely do get rained on, and water does get into there. And growers do use automatic over-head sprinklers.

Possibly a combination of water trapped and cool temperatures. Not entirely sure what is behind the rotting though.

Doesn't look good for that particular bulb - but at least the other bulbs and leaves look just fine.

Instead of physan (for the future that is) ...... can consider systematic fungicides (eg. thiomyl, monterey garden phos, copper spray etc).

Ok I will definitely use systemic next time. I don't get it with this plant....I've never seen it bloom because the new growths keep doing this. This particular growth is growing 90 degrees from the upright ones and has nothing in the sheath. Last one was blind too. Thing has me baffled. For a hybrid she is awefully fineky. It probably did get water in there cause of the way it's growing....ugh I'll try again for next year.

What water are you using? What fertilizer are you using? How much calcium is it getting?

I use rain water. Msu fertilizer weakley weekly kelp max once a month as per the bottle and calmag once per month. I just cut the growth 😭 omg this hobby is so emotional 😂

What is weakly weekly? How much fertilizer per what volume of water? How much Cal-Mag per what volume of water?

I mix 1/4 of a teaspoon of msu per gallon. And one teaspoon of calmag per gallon.

Dying back of new growths can be due to insufficient calcium. I would guess some plants are more sensitive to it than others. Try giving the plant more calcium. I am going to post this message, work on it some more, then come back and post again with some suggested concentrations of fertilizer.

In the mean time - your water utility publishes a water quality report online every year. Can you try to find that? Let us know the pH of your tap water, and also how much mineral content your water has. It might be reported as total amount of magnesium and calcium or total dissolved solids (TDS.)

Ok great thank you. I am new to this about 18 mos in to a lifelong orchid journey of love, confusion, and some heartbreak. I would love to get better at feeding I just don't understand the numbers required yet. My tap water is straight up clorine and flouride. I won't even water my houseplants with it . I have a ph meter and a tds meter.

There must have been a reason for you to remove the sheath in order to see the 'rot'.

Did water get trapped in sheath and bulb surface?

It sounds like the fertiliser and mag-cal you apply is ok ---- as in the schedule.

If temperature and light requirements are good, and the nutrients/elements are good, then also focus on what's happening with the water. Does it get trapped in the sheath? It might not be the cause of the issue, but will be good to consider.

Also, is there gentle air-movement in the growing area all the time? That generally helps a lot to cut down on issues.

I have fans going 24/7. It makes sense with the water getting on this particular growth because of the way it was growing out at a 90 degree angle. The last growth that did this came from the grower and the spot was not under the sheath as this one was. I'm going to def going to be more careful when I water now that they are inside. It was only under the dried sheath I peeled off and didn't go to the base of the bulb or into the rhyzome. It probably would have if I hadn't caught it. Win win for me but no blooms and more knowledge 😁

I don't think you have a fungal nor bacterial rot problem. I think lack of calcium is more likely. Cattleyas are particularly susceptible to this, and lack of calcium causes exactly what you describe.

Systemic fungicides are only useful if you know which fungus your plant has and you also know whether that fungus is susceptible to the fungicide. Blindly using fungicides may not work. Plus, it can kill beneficial organisms that prevent worse problems.

I am asking about your tap water because I want to know how much calcium it contains. It would be cheaper than buying Cal-Mag to mix your tap water with rain to achieve the desired calcium. Chlorine and fluoride ion added to tap water are in such low amounts it doesn't harm most plants, including Cattleyas, so don't fear using it.

I mix some of my high-mineral tap water with rain, and add a little vinegar to adjust my pH. I also add a small amount of fertilizer. In this way I don't need to buy Cal-Mag and my plants get lots of calcium and magnesium.

Less expensive TDS and pH meters aren't usually that accurate. Your utility water quality report will have more accurate information.

ES could be right here. Anyway, if the orchid happens to have a serious element deficiency ---- then if its cells die as a result of it, then the death of the cells will lead to decomposing/rotting.

LMO ------- was that brown coloured region of the bulb soft and mushy?