Dark patch on Cattleya pseudobulb?
 

This is a cattlya which has developed a brown patch on the base of the pseudobulb (arrowed). It is firm, not soft at all. This is the last pseudobulb, and the new one is to the right. Air circulation is provided by a fan. We are worried in case this is rot oir fungal or bacterial infection and would value any advice you can offer.

I see two possibilities. If it is sunburn, the plant may cope with the damage.
If it is fungal rot -what I think is more likely - there is nothing you can do and the plant is lost.

You could treat it with hydrogen peroxide, Physan or an anti-fungal just in case. I have had brown marks on my pseudo bulbs before and they were fine but it depends what it is.

This is probably soft brown rot. This is also potted in way too large a pot for it's size. The media stays too wet for too long a time. Leave this alone and if the plant can't handle it, the pbulb will fall off. If it gets soft and the pbulb starts to fall over, then cut it off with a clean razor blade and treat the wound with powdered cinnamon.

This is exactly what happened to my cattelya that I am vainly still trying to rescue. Btw, when listerine, alcohol or hydrogen peroxide is recommended to treat crown rot and fungal infections, what are we actually talking about? Do we dilute the listerine and the alcohol? and by how much? I have isopropyl alcohol and also bought a bottle of original listerine. I should dilute the listerine before spraying on plants with fungal spots?


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Do you see the sheath material on the new pbulb? That is fungal growth. As long as the plant is healthy it can cope with this fungal attack. But the old pbulb is no longer growing and becomes fair game for fungal rot. Keep it dry. ASs said this pot is way too large for this plant and stays too wet for too long. The new growth has no roots or if there are new ones growing they are short and immature so aren't taking up enough moisture nor food to keep it going. So that is why I suggest keeping the old pbulb until it falls off by itself. It is still a part of the rizome and the new growth is pulling it's reserve of moisture and sugars from it. Leave it alone and water sparingly.

Thanks. The old ones gradually fall off. The current new one is still ok. Patience is not one of my virtues unfortunately. ;).


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I would first wait a couple of days to see if it spread any further. If it does, then I would unpot the plant, cut that brown area off.

Repot the plant and hope for the best.