Mass Phalaenopsis Root Rot Situation?

[Roberta]

I never soak my bark - Orchiata, especially. I just water a freshly-repotted plant more often. Those air spaces are a benefit not a detriment. These want "humid air" not "wet" around the roots.

[tmoney]

i dunno, your original photos don't look too awful bad. i probly wouldn't have even bothered with it.
although, we tried capping our medium with sphag to retain moisture and it honestly worked too well, even when the top coat was totally crispy. so we ripped it all off and don't do that anymore.

i'd be happy with those roots! but for sure the practice of not mixing water is the first mot basic step to plant hygiene

[jje10001]

Originally Posted by tmoney

i dunno, your original photos don't look too awful bad. i probly wouldn't have even bothered with it.
although, we tried capping our medium with sphag to retain moisture and it honestly worked too well, even when the top coat was totally crispy. so we ripped it all off and don't do that anymore.

i'd be happy with those roots! but for sure the practice of not mixing water is the first mot basic step to plant hygiene

The roots on most of them weren't too bad and aside from one severely-impacted plant, none are displaying signs of dehydration post-repot...but they were far better looking before the mass rot incident. It was definitely some sort of infection, the roots would darken slightly and go mushy (velamen pulled off easily), before turning completely dark brown with a liquid interior and a foul smell.

I've definitely stopped using sphagnum to cap off bark, keeping it only for the paphs that need the moisture, and I've never really shared water because of the fear of viruses.

[tmoney]

uggh, yeah that sounds gross. sorry to hear, but an interesting thing to be on the lookout for!

[jje10001]

Just saw this video from Norman Fang with a Phal Bellina in a similar predicament- overwatered with rotten, dark roots.

https://youtu.be/6xtwV4e7bQQ?t=1235

At this point he mentions that a cause of this is a fungus that attacks roots, found everywhere in nature. I wonder which species it is? I have also noticed that some severely affected plants, there have been some secondary instances of rot on the leaf sheafs on the stem (doesn't seem to extend beyond the outermost layer).

Perhaps this fungus may have appeared with the arrival of summer (warmer temps) & the opening of the windows? With overwatering and souring media, this would have provided the perfect moment for an attack. One thing I should add is that the affected phals were largely acquired from around December 2021 onwards- and this event occurred after the windows had been open for awhile in June.

He trims the roots quite aggressively and then dunks the plant into a Physan solution before leaving it to dry for a week or so. I personally only dunked some of the plants, but I did wash them in the sink. I then potted them up into rinsed leca and did not water them. This week I watered the phals ink the sink with the nozzle, no fertilizer for now.

I think that the fungus is still around since some of the repotted roots are dying off, but I think that falls under the category of root stress (from the trimming & repot), so I won't do anything about it for now aside from keeping an eye on them.

[jje10001]

So a small update-

Of my collection, I repotted five hybrid phals into leca, and the rest back into bark.

The hybrid phals potted into bark (some even back into their old bark) seem to have recovered and are sending out new root tips, while the hybrid phals repotted into leca are mostly unhappy about it, and continued to struggle and rot their roots.

Of these five, one has happily accepted the change in substrate and is sending out a flush of new roots, another was both rotting its roots and growing a single lonely new root tip (so it went back into bark).

Of the final three, two have lost nearly all their roots save for a couple near the surface, and though the leaves remain turgid, are still not in the recovery phase yet. The final one has contracted an advanced stem rot, and I expect to lose it.

Lesson learnt! If an orchid is stressed with rot issues, best put it back into a medium that its remaining roots are used to...

[estación seca]

It looks like they were suffocated. The rot was in the areas farther from the air. That suggests to me in your growing conditions you should use medium with larger chunks and larger air spaces.

What are your ambient temperatures through the year?

[jje10001]

Originally Posted by estación seca

It looks like they were suffocated. The rot was in the areas farther from the air. That suggests to me in your growing conditions you should use medium with larger chunks and larger air spaces.

What are your ambient temperatures through the year?

Roughly 20-25C/68-77F, but the humidity drops below 30% in winter (it's around 40-50% at the moment).

The interesting thing is that there was explosive root growth for several months from winter into spring, but then a mass rot at the start of summer.

My speculations were that the drier temperatures during winter and spring + the fresher medium complimented my weekly watering regime, but then as the temperatures & humidity rose, the medium being constantly moist (along with some slow-release fertilizer) decayed & compacted faster, and became host for aneorobic conditions, finally triggering some form of infection.

[estación seca]

Your humidity range is fine and wouldn't cause this. Phal roots are fine constantly moist if there's good air circulation.

Closing off of air spaces would cause this, but what I see in the pots looks good enough not to cause this.

I wonder whether you made a mistake once and mixed the fertilizer far stronger than you intended. That could cause this.