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.)