Mass Phalaenopsis Root Rot Situation?

[jje10001]

Hi all,

Just an emergency- this week some mysterious root rot infection has spread really quickly among a section of my phalaenopsis collection.

The last week these phals were still healthy and growing roots, but over the course of a week, many roots started darkening and getting mushy all at once, accompanied by the appearance of fungal filaments. Some of the sphagnum at the top of the pot also started getting moldy, for some reason (never happened before this).

The rest of the plant seems unaffected, and phals that were grown drier, or located away from this particular collection also seem unaffected.

These phals were all potted in orchiata mixed with leca, with a bit of moss at the top, and there was a fan running in the room during the day.

Any ideas as to the cause? Not sure if it's fungal or bacterial, nor of the ways to treat this (I don't have access to systematics where I am).

[Roberta]

Photos? When were these particular plants repotted? The fact that others, that were drier, don't have the problem is a big hint that the medium went bad. I hope that you have not been sharing water amount the plants! That can spread a problem from one to its neighbors very fast.

[jje10001]

Reply in the comments to keep things clear:

Originally Posted by Roberta

Photos?

Examples of darkened, rotted roots- they take on a mushy dark brown-green form, sometimes with fungal filaments growing on them.



Nearly all the roots on this side of one of my phals are darkened and mushy-looking.


The roots/medium smells rank (even ammonia-like), and even some of the lighter roots are soft and tear easily from the root strands.


An example of what was left after clean-up on one of the phals, removing all mushy bits.

Originally Posted by Roberta

When were these particular plants repotted?

They were recently repotted, over the course from January-now. Some were potted in as little as a month ago. So the medium is still relatively fresh, though some of it has been kept in moister conditions.

Originally Posted by Roberta

The fact that others, that were drier, don't have the problem is a big hint that the medium went bad.

Definitely moisture has to do with it, I have some that were not yet repotted from their sphagnum cups which are untouched, and another potted in leca which is also untouched.

But the simultaneous infection and appearance of root rot throughout several otherwise healthy growing plants, all at once, makes me suspect that this is an introduced infection that thrives in moister environments.

One thing that I noted is that several of my other phals not located near these affected phals did not seem to suffer from any of this root rot.

Another note is that I added a small amount of Dynamite slow-release fertilizer a few months ago to many of these plants (which are watered with plain tap water)- I wonder if there was gradual nutrient build-up which ended up exploding into this current issue? I recall that overfertilizing can cause a lot of these issues as well.

Overall, I think this is a infection that spreads plant to plant, or via the air. However, I'm not sure as to what exactly it is, nor of the way to treat it.

Originally Posted by Roberta

I hope that you have not been sharing water amount the plants! That can spread a problem from one to its neighbors very fast.

No water was shared, but they were in relatively close proximity to one another. The windows were open throughout this month, and a fan was running in the room.

[Roberta]

The fertilizer might very well be the issue - so not rot from the outside, but killing roots. The time-release fertilizer actually responds more to temperature than to water. So if they got warmer, they got a blast. Phals don't need much fertilizer. I would suggest just repotting without the fertilizer, and let them recover. I would not do any "surgery" - a root that has lost its velamin can still hydrate the plant, and helps to hold it place firmly.

[jje10001]

Originally Posted by Roberta

The fertilizer might very well be the issue - so not rot from the outside, but killing roots. The time-release fertilizer actually responds more to temperature than to water. So if they got warmer, they got a blast.

An alternative is that I have been overwatering these plants, as I water once a week, while the medium is slightly damp and the roots are still green (prior to this incident, these phals were extremely vigorous root-growers)- I believe that Dynamite/Nutricote is chemical release rather than temperature release, meaning that it may been primarily activated by water, and that some of these pellets stuck deeper in the pot could have been slowly releasing nutrients non-stop.

Regardless of the cause, the overdose of nutrients could have weakened the roots, while providing the right conditions along with the moisture to trigger a fungal/bacterial bloom. Some of my phals which were not fertilized still contracted these root rot issues at the same time- meaning that it was likely not purely due to the poisoning of the roots.

Originally Posted by Roberta

Phals don't need much fertilizer. I would suggest just repotting without the fertilizer, and let them recover. I would not do any "surgery" - a root that has lost its velamin can still hydrate the plant, and helps to hold it place firmly.

Another phal cleaned up- the general pattern seems to be that the roots closer to the bottom of the pot & in the center are more likely to rot, and that there wasn't any poisoning signs like blackened tips- instead the velamen simply became soft and rotted off.

This phal & it pot had a rank ammonia-like smell to it, including the orchiata- does this hint towards a particular cause, and can the medium still be reused?

[Roberta]

Originally Posted by jje10001

This phal had a rank ammonia-like smell to it, including the orchiata- can the medium still be reused?

I would not re-use medium. Put it in the garden. When you repot, rinse the plant well under running water. As far as frequency of watering goes... it will vary depending on medium and heat and humidity. If you water only once a week and the bottom of the plant is still wet, something needs to be adjusted... If well-drained (like with medium/large bark) or mounted, you could water every day and it would not be too much. So your goal is to get better air circulation around the roots. There are multiple ways to accomplish that, but keep the goal in mind. When you water, do it so water runs through the pot - which flushes out fertilizer salts and other crud, and also pulls air into the root zone.

[rbarata]

Nitrogen => Over watering + degraded medium => Anaerobic bacteria => Amonia

Repot with fresh medium and stop watering so much

or

Repot with a less water retentive fresh medium and keep your watering scheme and monitor the results.

[jje10001]

Originally Posted by Roberta

When you water, do it so water runs through the pot - which flushes out fertilizer salts and other crud, and also pulls air into the root zone.

This was the way I watered the phals that had the slow release fertilizer, strangely enough- running the pots under the sink.

Originally Posted by rbarata

Nitrogen => Over watering + degraded medium => Anaerobic bacteria => Amonia

Repot with fresh medium and stop watering so much

or

Repot with a less water retentive fresh medium and keep your watering scheme and monitor the results.

Thanks for the clarification, I guess this could have been a long time in the making.

I will definitely switch over to a faster-drying mix when I go through cleaning up all these phals.

That being said, my newly potted phals (<1 month) were similarly affected- can this anaerobic bacteria spread from plant to plant?

[Roberta]

Originally Posted by jje10001

That being said, my newly potted phals (<1 month) were similarly affected- can this anaerobic bacteria spread from plant to plant?

Definitely. Also, they are in the environment. If the conditions are "friendly" to them, they will multiply. So rinsing well, and then giving them a new environment with less water and especially more air will solve the problem. Air is really the important thing here - roots don't suffer from too much water, but rather from not enough air. In nature, Phals grow on the branches of trees. They may get rained on every day, but then dry out, and of course get lots of fresh air. We put them in pots because we don't have the high humidity that they would get in the tropics (and makes it easier to manage them in our homes). But that need for "moist air" rather than "wet" is still vitally important.

[jje10001]

I ended up transferring a significant number of the grocery store phals to a leca-charcoal mix for the time being to promote proper airflow and weekly drying.

One of the largely unaffected phals had some exposed roots poking through the bottom of the pot that occasionally sat in a bit of water in the cloche pot, and I noticed that those roots were later affected by the rot as well- but once I cut those roots off & raised the container above the pot base on some styrofoam, the rot went away. It's strange as I had many phals with 'wet feet' for months without issue, up until now. It's unfortunate, I feel like my phals liked the extra moisture and rewarded me with lots of growth and new roots even into the bottom of the pot.

I am wondering about one thing though- for many of the affected phals, I soaked orchiata beforehand in hot water to open the bark's pores, but at the same time I do hear that it's advised to avoid washing/wetting orchiata beforehand since it has a dolomite application to buffer the ph. I wonder if this action might have 1.) Made the orchiata too water-retentive given my watering schedule and 2.) Removed some of the ph buffering, making it acidify much more quickly in an environment of near-constant moisture? Some food for thought for me.