Fusarium wilt outbreak advice needed

[KatKate]

Where do I start. This summer I have moved to a bigger house and I decided to indulge in my passion and add more Phals from my long wanted list. I have bought several new Phals from different nurseries and stores (Dutch suppliers mainly) from both sources. Before this summer I had already quite a few orchids (Phals, Dendrobiums, Paphiopedilums) for several years and they were not complaining or diseased so summer was quite good until I suddenly lost one of the orchid purchased 1 month before that from a dry rot. I disposed of the remains. Then a second one that was not so far from it (by quarantine principle) and purchased also around 1.5-2 months before that perished from the same nasty rot. That’s where for the first time in my experience I met with Fusarium (purple tissue around the rot for the orchid not known to display purple pigment). Worse comes next. I have discovered the first signs of the infection (stem mainly with roots looking as brown/blackish buds not coming out, and roots - in one case super purple tip of a newly growing root) in several of my Phals. I really do not understand what I do wrong or if it is a Superbad coincidence and they were already purchased this way.
But: those cases were in different parts of the house, scissors for pruning are always well disinfected with ethanol, no water is shared between the plants. Those cases that were really rotten were carefully disposed of. Those cases that are suspicious or with beginning of the dry rot, I isolated them and treating them as much as I can as I want to save them. We cannot get strong fungicides here where I live and frankly do not want to use the dangerous ones, so I use bacillus subtilis “prophylactic” treatment since the “outbreak” started. Bacillus subtilis was shown to prevent and sometimes treat different rots including fusarium ones. I also sprayed 3% oxygen peroxide where the roots were suspicious. I was hesitant to repot the majority of these cases, as the original substrate seems to be ok (good drainage, not decomposing). I have been doing the treatment for a month now. Unfortunately I do not see the signs of improvement so far. Would anyone have an advice on that, please! I am kinda lost and depressed, do not want to throw out the plants preventively, there are all very beautiful and some of them quite rare. Thank you very much in advance!!!!

[Shadeflower]

sry to hear!

So is it only the newly puchased ones showing problems or are you now worried that others in your collection might have picked up problems from the new arrivals?

[KatKate]

Thanks a lot! My old ones seem to be going strong (knocking on the wood) and those are my recent ones that are displaying fusarium infection symptoms. Nevertheless shame to throw them out. I want to know if anyone could confirm, please, that first signs of fusarium are not definitely a death sentence and can be reversed with any treatment. I also ordered Trichoderma for additional treatment, awaiting it now.

[Shadeflower]

I can't say for sure whether I have had fusarium or not, I know not everyone thinks it is a death sentence.

It's just a fungus even if a very fast aggressive one.

I reckon I have had it and stopped it spreading. Just through good growing practices, I know of others that also believe it isn't necessarily a death sentence but at the same time it is aggressive and can easily spread and kill an orchid fast (if that is what I had).

On monopodial orchids like phals that only produce one growing direction if they get infected it can be very tough to save them cause it involves keeping the orchid as dry as possible but the roots need to stay hydrated and that is hard with a phal where both are very close to each other.

I have seen good success videos of growers cutting out the fusarium if it is caught early enough but often you start cutting and cutting and then there is nothing left to save...

I don't really like the cutting approach.

Pictures might help you get better advice on the matter.

I haven' bought any orchids lately but there is one nursery in particular I did have quite a few problems with in hindsight. Happens. Transport stress can weaken them enough that it can be very tricky. But when you do find a good nursery to buy from, just use that religiously, the place the orchid came from can make a huge difference.

I will make a post about this sometimes next year. I have plants I bought at the same time from different vendors and none of them grow the same. Some have remarkable differences ie some are just healthier than others!

[KatKate]

Totally agree with everything said. And I want to avoid cutting approach too as sometimes purple color from fungus comes very deep so indeed there will be nothing left to save once cut. Posting the examples of 2 plants with their stems and roots accordingly. Roots look good except for purple tip (hidden from light in the pot, so doubting its “innocence”. And the stems are not looking very good these are relatively “good” examples among my cases.

[KatKate]

Publishing here an example of a worse case. Again, roots are fine but the stem with roots are more than suspicious. Moreover a young leaf was growing nicely until It stopped and became dry on the edges... green color on roots is brilliant green that has anti fungal properties, does not dry anything, just thought why not try it. The roots were already crooked like that upon discovery. The suspicion started when I saw that the blooming stem Started drying promptly from the base....

[Orchid Whisperer]

Originally Posted by KatKate

Publishing here an example of a worse case. Again, roots are fine but the stem with roots are more than suspicious. Moreover a young leaf was growing nicely until It stopped and became dry on the edges... green color on roots is brilliant green that has anti fungal properties, does not dry anything, just thought why not try it. The roots were already crooked like that upon discovery. The suspicion started when I saw that the blooming stem Started drying promptly from the base....

Kate:

I see nothing in the photos that suggests fusarium. The purple color on root tips can be completely normal.

Reading your first post, the 3% oxygen peroxide confused me (did you mean hydrogen peroxide?). Hydrogen peroxide is an oxidant, and damages or kills roots. I have been growing orchids since 1982, I never use hydrogen peroxide.

Regarding your plants that you think may have fusarium, can you show other pictures that include leaves? The most recent photo does not look like fusarium; maybe low humidity?

FWIW, I had fusarium in one plant (a Cattleya) about 20+ years ago. I removed affected tissue (easier on a sympodial plant), provided good culture, I still have the plant and it blooms regularly.

[Shadeflower]

I have far worse looking phals that are absolutely fine.

I agree with orchid whisperer 100% Nothing to worry about there. The black root nubbins are not great and do keep an eye on it but the phals should grow out of it without issue. I'd be really surprised if any did not.

Fusarium infects the stem and literally makes the stem turn brown. Roots are disposable (ok not quite but not as serious as a brown stem by any means)