Help ID this discoloration of the cattleya leaves

[PeteM]

Hi all.

Was hoping some of the advanced growers can chime in. I returned from vacation (5 days) to find a few cattleya leaves of different plants showing large brown/ purple patches in the leaves, random solid patterns covering mid section of the leaf to the full leaf, but not near the base of the plant. You can see the discoloration on both sides of the leaves. Pictures included below. Very scary how fast these leaves changed colors.. I was gone 5 days.

While I was gone It’s been hot in Baltimore the past week but the grow room temp never rose above 80. I left the house sitter in charge of the orchids with my normal watering schedule, per cattleya this includes a daily mist of the roots using RO water that has been amended with 25-50ppm balanced fert. Never had an issue with this before. The orchids are usually watered at 5-7pm, lights out at 11pm.

One issue occurred when I was gone. The power was cut due to an issue in the neighborhood starting at 1-2am until 5pm the following day. During which the basement orchid room was dark with no led lights and stagnant with no fans operational for close to16 hrs. During all this the temps were in the low to mid 70s.

I’ve ruled out sunburn and virus. Can anyone tell off the top of their head if these leaves look to be impacted by a fungus or bacteria? Or maybe there is a deficiency of some type what h has caused the onset. Or maybe they were over fertilized with something?

What’s strange is it’s only random cattleya orchids, and seems to impact plants scattered around on both of my grow tables.

What a mess. I plan to physically remove the leaves and treat the pots and surrounding plants with physan and clearys 3336.

Any insight would be much appreciated

Thanks!

 

[big923cattleya]

I am thinking black rot. This was a huge problem for me when I was in Florida. The warm, humid conditions had a lot to do with it. At one point I was losing 10-12 plants a day. I grew about 100 Cattleya seedlings at that time. Rot would appear, I would cut and treat but things would die in about three days.
Mature plants went a few days longer but died as well. How did I stop it? I started a monthly fungicide program and increased my air movement. Plants were outside in a lanai but by having 2 16” oscillating fans on 24/7, helped to control it. Where I was losing 20,30 plants in a week, I lost one or two per week. I swear you see the rot spread as you stared at it.
Once it gets into a plant, I tried trimming every black area back to clear green tissue. That never was effective. It was like the rot had already spread past that point!
Good luck.

 

[PeteM]

I am thinking black rot. This was a huge problem for me when I was in Florida. The warm, humid conditions had a lot to do with it. At one point I was losing 10-12 plants a day. I grew about 100 Cattleya seedlings at that time. Rot would appear, I would cut and treat but things would die in about three days.
Mature plants went a few days longer but died as well. How did I stop it? I started a monthly fungicide program and increased my air movement. Plants were outside in a lanai but by having 2 16” oscillating fans on 24/7, helped to control it. Where I was losing 20,30 plants in a week, I lost one or two per week. I swear you see the rot spread as you stared at it.
Once it gets into a plant, I tried trimming every black area back to clear green tissue. That never was effective. It was like the rot had already spread past that point!
Good luck.

I think you are right. I’ve not come across anything else that moves this fast and the conditions were right for this to take hold even if it was just one day with no light or airflow. On top of this my sitter watered when the lights came back on for a few hours before turning off again so it just compounded the issue.

I treated for black rot, sprayed down the impacted plants and surrounding plants with physan and clearys 3336. Let it all dry and then I removed all infected tissue way below the current browning. Most of the impacted plants were mature, hopefully I caught it in time.

I need to get on a spray schedule. I’ve been reluctant to do so and only when needed but might be good to be proactive going into these next few hotter / humid weeks.

 

[big923cattleya]

Once I got on a monthly spray program in 2010, I have not stopped. I use Neem Oil at one tsp. Per gallon. I have a 1 1/2 pump sprayer.
I know people will have different ideas but I like Neem. It is both a fungicide and anti bacterial. It smothers insects and is a systemic. I started using it in Florida.
Since arriving here, I have not had a single issue with a rot.

 

[southernbelle]

Gosh, Pete, this is awful. Wish I had some insight. The only observation I have is usually bacterial rot spreads with a yellow area around it, I thought. I don’t see any of that in your case. It’s really weird how sharp the edges of the black areas are on some leaves and the patterns are bizarre. Let us know what you determine this is. Hope your treatment works!

 

[big923cattleya]

Black rot is listed as a fungal rot, not bacterial. That is why it spreads so quickly
This particular rot spreads primarily by splashing water droplets. It quickly enters the plant through stomata I would imagine and the mycelia, or fungal threads quickly envelope the tissues of the plant. Apparently the blackish color appears after the fungal tissue has quickly infected the area. so when one treats and trims off the blackened tissue, the black rot has already passed that area.
In Florida, I saw a 3" potted Cattleya seedling of mine with a black leaf or two plus a blackened pseudobulb early in the morning. I would quickly cut and trim removing tissue. The next morning instead of 20% of the seedling being affected, 50%+ of the remaining tissue was black. By morning three, 95% of the seedling was black. This is very quick, very aggressive! Unstoppable in seedlings, nearly impossible to stop in adult plants.
Prevention is what worked for me and GREAT air movement is essential.

 

[Ray]

I am generally opposed to any preventive use of pesticides, and have found that regular use of probiotics, reinforcing the beneficial microbes rather than killing then all, has essentially eliminated any rots in my collection, as well.

 

[dodidoki]

Dear Pete, i think it is bacterial rot, pseudomonas cattleyae. My experience that if a plant got sick from that, will die.

 

[southernbelle]

Black rot is listed as a fungal rot, not bacterial. That is why it spreads so quickly
This particular rot spreads primarily by splashing water droplets. It quickly enters the plant through stomata I would imagine and the mycelia, or fungal threads quickly envelope the tissues of the plant. Apparently the blackish color appears after the fungal tissue has quickly infected the area. so when one treats and trims off the blackened tissue, the black rot has already passed that area.
In Florida, I saw a 3" potted Cattleya seedling of mine with a black leaf or two plus a blackened pseudobulb early in the morning. I would quickly cut and trim removing tissue. The next morning instead of 20% of the seedling being affected, 50%+ of the remaining tissue was black. By morning three, 95% of the seedling was black. This is very quick, very aggressive! Unstoppable in seedlings, nearly impossible to stop in adult plants.
Prevention is what worked for me and GREAT air movement is essential.

Thanks, I guess I’ve never seen fungal only bacterial.

 

[big923cattleya]

You are welcome belle!
This was just a devastating problem for me in Florida. I too had never seen anything like this before.

 

[PeteM]

I am generally opposed to any preventive use of pesticides, and have found that regular use of probiotics, reinforcing the beneficial microbes rather than killing then all, has essentially eliminated any rots in my collection, as well.

Thanks all for taking a look. Your input is helpful . I was just chatting with Deborah about how upset I’ve been with family and friends facing health issues that it really distracted my husbandry this past spring.

There was a great article in the July 2023 issue of AOS Pg 494, Sue Bottom ‘Fertilize Weakly weekly’. Offered for the ‘Novice’ but it includes a very technical look with tables on fertilizing with RO water in the summer and increasing the amount of calcium and magnesium accordingly. Something I have slacked off on in the past few months and weeks. I do push these plants very hard with daily watering but I have the conditions to get them dry enough to grow well until I lost the fans during the long power outage. Additionally the article mentions ‘If you supply too much fertilizer to your plants, you run the risk of having lush, soft growth that is more easily attacked by pests and disease’. For this I am also guilty and have made adjustments to my watering / fertilizing routine. Trying to push my plants in the growing season.. I forget what a balancing act it can be at times.

Having a backup battery for the fans and the sump pump are on the list for grow room improvements. Also as Ray mentioned, keeping up with probiotics, calcium and other supplements to increase the resistance of these plants is something I can’t afford to lose focus on in the spring / summer transition. With the night temps not dipping as low in the height of the summer.. the plants won’t be able to store as much energy as they do during other times of the year and are probably the most stressed during this time of year.. for me anyways.

I was really sad to have cut large leaves and pseudobulbs off Friday on plants that have taken years to grow. I’ve set back a few but so far it doesn’t look like new rot has popped up. Fingers crossed I caught it in time.

 

[Guldal]

Thanks all for taking a look. Your input is helpful . I was just chatting with Deborah about how upset I’ve been with family and friends facing health issues that it really distracted my husbandry this past spring.

There was a great article in the July 2023 issue of AOS Pg 494, Sue Bottom ‘Fertilize Weakly weekly’. Offered for the ‘Novice’ but it includes a very technical look with tables on fertilizing with RO water in the summer and increasing the amount of calcium and magnesium accordingly. Something I have slacked off on in the past few months and weeks. I do push these plants very hard with daily watering but I have the conditions to get them dry enough to grow well until I lost the fans during the long power outage. Additionally the article mentions ‘If you supply too much fertilizer to your plants, you run the risk of having lush, soft growth that is more easily attacked by pests and disease’. For this I am also guilty and have made adjustments to my watering / fertilizing routine. Trying to push my plants in the growing season.. I forget what a balancing act it can be at times.

Having a backup battery for the fans and the sump pump are on the list for grow room improvements. Also as Ray mentioned, keeping up with probiotics, calcium and other supplements to increase the resistance of these plants is something I can’t afford to loose focus on in the spring / summer transition. With the night temps not dipping as low in the height of the summer.. the plants won’t be able to store as much energy as they do during other times of the year and are probably the most stressed during this time of year.. for me anyways.

I was really sad to have cut large leaves and pseudobulbs off Friday on plants that have taken years to grow. I’ve set back a few but so far it doesn’t look like new rot has popped up. Fingers crossed I caught it in time.

We cross with you:

 

[Duck Slipper]

I am reading this…wondering why this hasn’t happened to me. A horrid heat wave over us, 98’ temps and sky high humidity. No break until 6 days out.
Warscewiczii seedlings, Leudemanniana seedlings and over 100 Rex seedlings. I think I’ll do a preventative spraying.

 

[Ozpaph]

any follow-up?

 

[PeteM]

any follow-up?

Yes all is well now. Our power issues were resolved shortly after the incident with no further interruption of the lights and fans.

I aggressively cut off all the leaves showing symptoms and treated everything showing symptoms with clearys 3336 and Phyton 27. I’ve had no reoccurring issues since. A few of the plants I cut have started new leads. I’ve definitely set a few back but I was able to save all the plants.