I’m convinced I have a virus of some sort on my Opuntias and also some kind of “black rot” decease. I don’t know a lot about viruses or diseases in Cacti but I’m certain there is something going on. Symptoms include stunted growth and “mottling” as well as black spots that are not related to overwatering or damp conditions. Any help would be greatly appreciated. Thanks.
Opuntia Invicta with “black spots” hasn’t grown much at all and seems unhappy.
The same also appears on this plant quite often.
Mottling and stunted growth in this Opuntia Basilaris
Mottling on this Opuntia Imbricata as well although growth is quite normal on this plant.
Hi Mark;
I think I can say I have had must of those problems over the years, they seem to be related to cold and damp or humid conditions, my Corynopuntia Invicta was just like yours maybe even worse, but it is now growing out of it , I did remove a few of the worst segments, Austrocylindropuntia shaferi was another plant that suffered very badly, but the three plants of that species I have are now growing well , after moving them to a more favourable position and keeping them a lot drier, a lot of Opuntias do secrete a sticky sap from the upper areoles if given to much water and this can be the start of many fungus problems.
Ray
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There is an interesting piece on the black rot in Michael Kießling’s book from a few years back. I had a few segments succumb to this one wet summer so it’s not just cold and damp but dank conditions generally. I now remove affected segments asap as it does spread downwards. I seem to recall I posted and autopsy of one segment around 10 years ago?
Affects some groups more than others. Tunillas seem immune but Tephrocacti very prone to attack.
Thank you Ray and Mike. The black rot type issue appeared suddenly last year towards the end of the summer when it was still quite warm and took out one of my Tephrocacti completely. The plant was really healthy and in full bud about to flower then just before the flowers opened it succumbed to this very quickly. No ideas where it came from but it has spread to other plants from there. It doesn’t seem to be any worse or better in cold and wet conditions than dry and warm, it’s persistent whatever the conditions. As you say Ray, I’m hoping, like you that my plants start to build up some kind of resistance to it and grow through. Thanks.
Cactus viruses are widespread in nature so it wouldn't be surprising if they exist in our collections too, especially as many cacti are distributed from vegetative propagation, which favors viral spread. The marks you show on some of the plants are consistent with descriptions of viral infection and if you google cactus viruses you will see lots of images of similar marks. Some viral infections will only show if plants are stressed, so feeding and repotting can often mask viral symptoms. Unfortunately viruses cant be treated, so the only remedy is to get rid of the plants. Lots of pests will act as vectors for viruses, especially thrips, so leaving infected plants in your collection risks spread to other plants. If you keep them it is important that you don't cross contaminate your plants with any implements you use for taking cuttings etc.
That iconic ring strip patter is indisputable.
It some kind of virus .
Maybe it's Sammons' opuntia virus
But identification will require LAb test.Or some test-kit.
ALL plant virus are Incurable so what kind of virus it is is not very important.
From taiwan. hot humid subtropical island.
Pachypodium grow like weed here.
(not really, but u get the idea hot sunny rainy)
I don't think the black rot is a virus. Having observed it in action I'm convinced it is fungal / bacterial and is halted prompt removal of the face Ted segment. However I looked at one of my 'rough' T geometricus at the allotment greenhouse earlier (where they get relegated to if they are badly marked) and noted that it has survived with two of its four segments affected- in this case the black patch dried out and hardened into a kind of callous. When I have more time I'm going to remove and cut up one of the infected segments to see how deep it goes -not as far as the core I'm sure as it would have spread further if it got that far. This particular plant has not grown for a couple of years and just persists.
I get black segments mostly on T. geometricus.
I've left them too before and they eventually dried out and changed to a crusty white.
I cut this one open to see it didn't appear to travel far from the surface ?
Whatever it is, it would be nice to prevent it though
