What products have you had successful results with treating brown leaf spotting/rotting diseases on multifloral paphs?

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Aug 14, 2014
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New York City
Unfortunately, my Paphiopedilum Hsinying Anita, which flowered for the first time in 2021 January with very good quality flowers, is coming down with something nasty. I had to cut down a few leaves a few months ago. I applied some Dragon's Blood liberally just in case. Whether that helped or not, the disease had not returned until now. It is striking again.
The bloomed fan is more than half way trimmed off due to the advancing symptoms.
The new growths (one is ready to bloom again and the other is smaller) are mostly fine but the diseases started on one of the leaves on the larger new growth, which is very upsetting.
My Hung Sheng General and other multis are fine. I have even dropped them off and had objects dropped on them causing mechanical damage and such, but they are all tough as nail.
It is so annoying when the pretty ones get hit by diseases.

Please share actual cases where you have dealt with leaf spotting/rotting diseases rather than just throwing random chemical and products names. Thanks!
I have sulfur based spray for home use which had badly burned my venustum a few years ago and I had not used it but kept them since I was not sure how to dispose of the leftover.
Fortunately, though, I rarely see diseases happening in my collection, I most do not need to worry about spraying.
This current one really sucks though, as I really liked the flowers.
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I usually use a tank mix of Thiomyl (generic Cleary's) and Mancozeb at 1.5-2 tsp per gallon each, and apply as both a foliar spray and pot drench, alternating with Phyton 27 @ 1.5 tsp/gal for a course of 2 treatments each, all spaced a week apart. Make sure to balance the pH of the Phyton to the range on the label.
If the lesion is small, and there's only one, you can often get an extra year from a leaf by excising 1/2" beyond it with a flamed scalpel and painting the wound with a qtip dipped in either Calcium hydroxide or undiluted Physan.
The bad news, which you probably already know, is: You'll likely never be absolutely rid of it, but you can keep the damage to a minimum. Some plants are just too good to toss.
Thanks, Tony.
I knew Cleary's and Mancozeb will come up first.
I understand that they are not super dangerous with PPE on, but they are designated for outdoor use specifically and so I'm not comfortable using those. I'm already suffering from bad seasonal allergies and respiratory issues. don't want to do anything that might potentially worsen what I have.
The reason I bought the sulfur-based fungicide was mainly because the product label says it is for both outdoor and indoor use. Maybe I should take the plant outside and spray on the older half dead growth and see how the plant reacts before applying it on the entire plant.
I am going to be travelling for a few weeks soon. It means that everything will go inside bags while I'm gone. I'm quite sure this plant will either be badly affected by the disease or dead without anything sprayed on it by the time I return.
At this point, I'm basically hoping that my Wössner Black Wing in low sheath will turn out to be very nice so I have something similar and won't feel too bad. The only thing about this WBW is that the plant is larger than I hope and it will only get larger as it ages.
Oh, well....
I think it’s important to separate the various causes of such damage, as there are many things that can lead to leaf defects, such as under-watering, over-fertilizing (whether that be a dosage issue or contaminated media), extreme pH issues, or pathogen attack favored by maintaining a less-than-correct environment. The first three often lead to leaf-tip issues, while the latter three (yes, an overlap) can lead to pockets of necrosis elsewhere in the leaf.

Heavy watering (flushing), controlled feeding, and careful media maintenance seem to work well at eliminating “chemical” issues, it that pathogen issues are most often about the environment.

FWIW, even with overhead watering, which I used to a routinely and now get when it rains, I have seen a marked reduction-, if not total elimination of such leaf issues since employing regular use of probiotics.

It’s not an instantaneous result in orchids, appearing to be more like a “gradual buildup of immunity”, but that may have been more related to elimination of the pathogen population in my growing environment and overall plant population, rather than prevention, where they seem to be now. In faster-growing plants - thinking specifically of impatiens - a single treatment seems to offer immunity for the entire growing season, although that may be due as much with the more-favorable environment of a rich terrestrial, soil medium over a typical orchid media, as that would allow a greater microbe population in the rhizosphere.

That said, I have also used higher dosages of plant probiotics as “cures” (stopped progression) for some rots, so it would seem that they can be fairly fast in orchids, too.

I think the bottom line, HP, is that you’ll be setting up less-than-favorable conditions while you’re traveling,so it might be worth extra probiotic treatment in advance to see if it helps prevent issues.
Thanks for the input.
I am quite certain that this has nothing to do with the culture, but a case of fungal diseases. A genetically weak plant that has been under attack by invading pathogens that are obviously winning the biological warfare.

I am a thorough waterer. So I don't just pour or sprinkle water which seems to be very common among plant people. I believe that the main reason why majority of my plants look good and do relatively well without regular repotting is that I rinse the pot content well every time I water my plants. I am also a light feeder.
Also, the fact that I rarely see sick plants in my collection (I can count the number of rotting issues in my collection of a few hundred plants in the last 10 years with my both hands!) indicate to me that the over population of pathogens are not very likely. If that was the case, I would expect to see problems all over or at least on quite a few plants. But that is not the case fortunately.

We talked about the benefit of using Inocur (I always mess up the name, sorry if it's wrong again) in the past. I meant to try one but never got around to it. I think some plants are just weak as many living things can be. Only the strongest survives and only under cultivation we try hard to keep them all alive. Some efforts seem to work. Some just don't. It's more case by case.
At this point, I just don't have the time to order something in and try before my trip.
I will just spray the sulfur product all over and then bag the plant up while I'm gone. I think this issue will be stuck in the back of my mind while travelling and I will be eager to see what the plant would look like upon my return.

As I mentioned in my reply to Tony, I am hoping that my WBW will bloom out nicely.
I am not feeling too positive about the prognosis of my Hsinying Anita.
I’m going to partially disagree with you.

While I will not say this is 100% the case, much of the time, a “weak” plant isn’t inherently less hardy, it just isn’t doing well because it’s not getting the correct overall culture. If it was, it would not necessarily be considered “weak”, but there are any number of cultural parameters that, if not “within the ballpark” for that particular plant, will make it seem so.

Within my own, limited collection, “weaker” plants are those preferring to not be so damned hot in the summer.

Another, fairly common example is folks who are good with in-home phalaenopsis culture, who consider Phal. bellina to be a weak sister, but if they grew it very hot, they would see it thrive.

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