BCSS - Forum

Hi, does anybody know what the two dark spots are on the right ball? there was only one spot and now it seems like it’s spreading as there’s two. Should I cut off the ball or try cutting the spots out maybe?

That is a common problem on this species in winter, to much humidity and fungus gets a hold.
First give it a good spray with bug gun fungal killer or something similar which should control the spread, move plant to a dryer place, but if it still spreads just take the segment off the plant before it spreads down inside to the others.

Thank you Ray, I removed the segment, used a sterilised Stanley blade, and I didn’t do a very good job of it to be honest. I cut away the first black spot and it just kind of popped off. Then there were two others close to each other and when I cut them I could see it looked discoloured deeper inside. Looks like rot to me but I don’t know.

I posted a similar ‘dissection’ about 10 years ago (maybe slightly less- time flies). There is a good discussion on this topic in Michael Kießling’s book on Small Opuntias. Some clones seem more prone than others. In the past I left the segments attached to one of my more ‘rough’ plants to see what happens and it dried out leaving a scarred segment from which new ‘clean’ segments then grow. Probably not recommended but interesting.
It also Occurs on a few other similar plants and I also conclude it’s related to high humidity.

Hi Mike, thanks for having a look and the advice.

I put this one under the lights that have the fan on them to try and improve the airflow. I have been moving the whole collection around quite a bit recently since we moved house so I’m shopping for a new shelving system and lights so I can put more plants together in front of the fan.

I had a look for the book and saw these two, one matches the author but then I saw the Pilbeam one called Small Opuntias and it made me wonder if there was a mix up?

Do you mean your segment had a fungal problem and you cut the bad parts out but left the segment on the plant. It dried up and then sent out new segments from the cut one?

I would’ve preferred to do that but I was worried that whatever causes these spots would spread to the whole plant, if it hasn’t already.

Do you think I could remove the top segment to try and start a new better looking plant? And if I could are there any tips for doing it?

Definitely the former, downloadable at https://cactuspro.com/biblio/en:kiessling though Mike should really be recommending the other......

Yes that’s the Michael Kießling book. I was being generic with my description. It’s out of print but you can download a PDF of it from here:
http://www.cactuspro.com/biblio/en:kiessling
The other book is still available.....
I didn’t try and treat the ‘rot’ in the affected segment on the old and tatty T geometricus and it didn’t spread to the rest of the segments. The ‘rot’ dried into a hard crust on the affected segment and the segment then grew a new one. The damage was limited to three or four areoles . In the dissection I posted the segment was removed and cut up and the ‘rot’ was widespread. I would leave your plant alone now . The wound should dry up and eventually be lost as the bottom segment becomes woody which is generally what happens to them in my experience. To be honest I find them hard plants to grow well which is not from want of trying! No doubt this will bring on a flood of very well grown plants.

Phil_SK wrote: ↑Tue Jan 05, 2021 8:50 pm Definitely the former, downloadable at https://cactuspro.com/biblio/en:kiessling though Mike should really be recommending the other......

Modesty prevents me Phil....

Thank you for the recommendation and the link to the book. There’s so many different types of plants I’ve got it’s like spinning plates sometimes trying to keep on top of them all. Any time someone helps I really appreciate it.

Do you think it is a fungus on mine? And whether adding a fungicide to the water when I water it would help, as well as applying it to the outside like Ray said?

Mike you say you find it had to grow well this species, but I think plants with perfect olive green segments are difficult to grow but some how they are false, as every picture I have seen of these in habitat show plants that are very brown or woody with purple new segments, and some look so bad they would go on the compost heap if in my greenhouse.
What were the condition of the T. geometricus up in the roof of Michael's greenhouse in Germany when you where there, or am I thinking of someone else.