Fast spreading back (fungus?)

[orchidkaye]

Fast moving disease on my orchids. Help!!!! Please!!!!

[silken]

Isolate all that look like this and spray the rest with Physan or something similar ASAP

Spray the infected ones too in the hopes of arresting it. I am not familiar with that exact issue. Is the black area soft and mushy or firm?

[tucker85]

Cut the infected leaves off immediately and treat the plant with a fungicide. That's black rot and it can kill a plant very fast. Isolate the plant and definitely don't let water drip from that plant onto anther orchid.

[orchidkaye]

The areas are kind of mushy. The leaves fall right off as soon as the black reaches the base of the leaf

[james mickelso]

This is black spot and the leaves with it should be cut off all the way to the pbulb. Do not water this plant for at least a week afterward and isolate it from all your other plants. This should have been caught when it first started at least a week ago. You may lose this plant. I would also take this plant out of the pot and wash all the media off the roots, treat with an antifungal spray and then place it in a pot with no media. Leave it in this pot in a medium light for at least a week to see if it continues to spread to the other parts of the plant. If it can be arrested by cutting off all the affected parts and sprayed with an antifungal, then leave it in the pot with no media and start watering the roots but not the pbulbs or leaves. Just keep watering the roots daily and if by the end of july there are no more issues, repot it in a coarse media like straight bark for the remainder of the season. Watch your other plants too. This can kill an entire collection rather quickly if not caught in time. Over watering is one of the causes of this along with overhead watering regime .

I am going to change my diagnosis because I get these two mixed up. This is most likely pseudomonas infection (acidovorax) and not black spot. Black spot starts in the roots and progresses upwards while the pseudomonas infection starts on the leaf surface usually and progresses from there. But all the same try and arrest it by the methods I outlined. This is serious stuff at this stage and can decimate your entire collection. It is very contagious. Sorry for the mix up. See www.staugorchid.org.

[Jayfar]

Probably this is Phytophthora or Pythium.

PP260/PP260: Black Rot of Orchids Caused by Phytophthora palmivora and Phytophthora cactorum

Black Rot | AOS

Isolate affected plants far, far away from unaffected plants and cut off all infected parts. It may be better to discard affected plants to protect the rest of your collection.

Get Phyton 27 and carefully follow label directions (especially wear rubber gloves when handling Phyton 27 prior to dilution; turn off all fans while spraying). Proactively treat all plants with Phyton 27, as they may already be infected, whether a rot is visible or not. Unlike Physan 20, Phyton 27 is a systemic and gets inside the plants to fight fungal and bacterial infections.

Thoroughly clean benches with bleach or Physan 20.

[orchidkaye]

Thank you so much for the help. I'm going to get on this problem today. I couldn't believe how fast these plants deteriorated. It's been raining for days and days in Florida where I live. Probably didn't help anything.

[tucker85]

Originally Posted by orchidkaye

Thank you so much for the help. I'm going to get on this problem today. I couldn't believe how fast these plants deteriorated. It's been raining for days and days in Florida where I live. Probably didn't help anything.

I thought you might live in Florida when I saw the picture. Every year a couple of my cattleyas will come down with black rot overnight. The plant will be healthy and green in the evening and in the morning the whole leaf is black. I try to use fungicides every 3 or 4 weeks during the summer. I've used Thiomyl, Dithane and Subdue. If you can find Subdue, it's a very effective systemic fungicide that works well against black rot. It's very expensive but a member of our orchid society buys a bottle and sells a little to each member who wants some. I would say regular use of Thiomyl or Dithane will help also. I'm not crazy about Dithane because it leaves a residue on the leaves but it has been an orchid industry standard for years. Many people use Cleary's also but I've never used it. Always cut off any leaf that gets black rot and throw it away, and treat the plant with whatever fungicide you have.

[rick84]

Please consider pro-biotics for future use and increased resistance to disease. Not a cure, but acts and is applied as a preventive.

[james mickelso]

Nice site. Thanks for the pointers. The difference I thought was that black rot started in the roots and progressed upwards while brown rot started on the leaf surface and progressed from there. Well ya loin sometin ever day.