HELP! Potinara new shoot black!

[ScottMcC]

if this is truly black rot, which from the description it looks to be, then you should take off that entire pseudobulb, treat the plant with a systemic product like phyton 27, nad be very vigilant for further spread. I had the same happen to one of my favorite cattleyas, and I was reluctant to trim back enough. sure enough, every few days a new bulb was affected until there was no plant left.

by the way, just for clarification--sometimes the sheath will indeed turn black, just as part of its involution process, and sometimes this occurs piecemeal. but in your pictures, it looks like the sheath was soggy and floppy at that area, which to me signals rot as opposed to normal sheath maturation. did you notice any odor?

[Helen]

Scott McC, Absolutely NO odour. This leaf/sheath? was not floppy until I tried to pull it out...it was getting softer as each day went by....not mushy, but very black and shiney...Because my roots are really only under this new shoot, I'm hesitate to cut the whole thing off...but, I could be wrong here. I'm very new at orchid growing, a real newbie....I hope that it wasn't the involution process, because then I've really screwed up by cutting it off. I was misting it periodically, so maybe water got in between and rot started....thanks very much for your help. Much appreciated!

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[Vic T]

Helen, I would do as Gloria suggested. Water early and not at all on cloudy days
Regards Vic.

[gixrj18]

Try mixing a biological water treatment such as HYDROGUARD or COMPANION 2-3-2. I would suggest the HYDROGUARD if your not in a greenhouse because the COMPANION has an odor due to the fish emulsions in it. I'm sure there are other products, just make sure it contains bacillus subtilus. This is a beneficial bacteria that eats fungus. I use it as a maintenance in all my nutrients.

[Oscarman]

Helen, I'm with Scott on this one.

BLACK ROT (Fungus: Phytophthora spp.)
Black Rot is a particularly aggressive infection of Cattleyas and other orchids caused by various species of the fungus Phytophthora. A new shoot suddenly turns black: the rot moves rapidly, killing the rest of the plant. A whitish 'bloom' of fungal tissue and spores may be seen on the diseased tissue.

This disease is more prevalent during the rainy season in the tropics where it spread primarily by splashing water. It can also appear in damp, poorly ventilated crowded collections.

Spores must be exposed to continuous moisture for more than a day for them to germinate and enter a plant part. Infection can also occur via cut surfaces.

SYMPTOMS: New growth quickly turns black, usually from the base up. White 'bloom' of spores on surface. Smells somewhat fruity.

CONSEQUENCES: Rot moves rapidly through rest of plant. Plant usually dies although aggressive removal of diseased parts together with adjacent healthy tissue can result in a cure. Highly contagious during rainy season in the tropics or in poorly ventilated, humid growing areas.

CONTROL: Disease spread primarily by splashing water. Stop watering/spraying and shelter plants from rain. Isolate infected plants. Burn diseased material. Wash hands after handling suspect material. Spray or dust with a locally approved fungicide.

[Ray]

The advice is good - keep cutting until you see no black coloration or even the slightest darkening. Sterilize the tool between each cut, or you could just transfer the pathogen to the fresh cut...