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Old 06-10-2021, 02:12 AM
camille1585's Avatar
camille1585 camille1585 is offline

Join Date: Oct 2007
Location: middle of the Netherlands
Posts: 12,968

Originally Posted by mvmgems View Post
Though as for fusarium occurrence, I'm not sure a low endemic rate in California necessarily rules it out? I only had this plant a few months and purchased from a grocery store who could have imported them from a tropical nursery (Hawaii or Taiwan). Given the short period of time I've had it, Occam's Razor would suggest it could have contracted an infection from the nursery and been asymptomatic until the multiple stresses involved in getting it to my home.
While I also don't think your plant has fusarium, I agree with this comment. While we must not be too quick suspect fusarium, we should also be careful about being too dismissive of it as a potential cause. Like you say, plants travel, and can come from places where the disease is an issue.

That being said, I found a nice information sheet some time ago about orchid diseases including fusarium in Phals and Paphs, put together by a large commercial orchid nursery in the Netherlands. It's in Dutch, but google translate will do the trick.
HARK Orchideen - Bacterie-, virus en schimmelziekten aan orchideeengeslachten

Here is a quick translation:

Fusarium is mainly a problem in Phals and Paphs and can be considered an opportunistic pathogen, infecting/spreading when the plant is in a weakened state mainly due to issues such as very high fertilizer concentration, low substrate temperature, excessively wet substrate or sterilized substrate (due to lack of beneficial micro-organisms).

On Phalaenopsis, infections are first visible as small yellow-brown to reddish lesions on the roots. The spots gradually become larger until forming typical dark rotten sections of root. The base of the plant usually has black, dry rot which gradually spreads upwards, and in high humidity, pink reproductive fungal spores will form. The youngest leaves take on a reddish tinge, then chlorosis appears which leads to defoliation and death.

In Paphs the infection usually starts at the point where the roots and base of plant meet. A wet rot then develops with individual leaves easy to pull out. Disease development is slow and plants often form new roots on the healthy parts of the plant. However, the combination with slow delayed growth is a sure indication of fusarium.

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Last edited by camille1585; 06-10-2021 at 02:35 AM..
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Old 06-10-2021, 06:38 AM
Shadeflower Shadeflower is offline

Join Date: Apr 2021
Posts: 98

Thx Camille,
that is quite informative and confirms my suspicions that fusarium is not always a death sentence.
Your info states the plants can still grow new roots, the fusarium just hinders this. This would indicate a couple of orchids I'm suspecting have had it/have it might have it.
As long as the black area is kept dry it doesn't spread but some people recommend cutting all the black away which is very extreme and would certainly set them back.
I just discovered the one case this week after peeling away some dried sheaths which were completely hiding it and I am suspecting the plant has had it for months already based on its recent slow growing behavior.

But the area is being kept dry and I was debating to do more but I will leave it and see what happens. The plant is still growing I think and is starting to develop new roots above the black area
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