San Pedros with a problem

Hi all
First off Merry Christmas to all!

Now here is my problem, I have seven San Pedro cactus plants, two large ones two medium ones and the rest in different stages of growth.

Unfortunately over the past two weeks I have noticed that three of my San Pedro cactus have been changing colour starting with a yellow patch followed by a much darker green colour along the side where the patch is located. See Photos.

Can some one tell me what is going on, is it what I think it is, the San Pedros are rotting away?
Thanks
Cristina

Cristina, It does look like they are rotting. Does the affected area start at the top and work its way down? Is it affected all the way to the soil line? Are the spots soft?

It's time to sacrifice one of your plants for the good of the rest. Cut the plant off in the middle of the affected area. If it's rot, the center of the cactus will be brown instead of the usual bright green and the texture of the tissue will be different.

You may be able to save some tips if you can cut all the rot off.

Daisy

Daisy

Yep the area is soft, and I did have to sacrifice one of them to see what was going on inside and this is what was up, look at photo.

As you can see the center is fine but the edges are like a dark green to brownish colour.

The one I cut open was almost all the way to the bottom. I was able to save the top 6cm of the cactus and the bottom 8 or 10cm upto the soil everything else looks like the Photo but in varying degrees.

What I did try was a trick someone here suggested which was rub ash on the affected exposed areas and let dry, they told me it should stop the rot . So I did that in the least affected pieces I cut off. now it is wait an see.

Can you suggest anything else?
Do you know what may have caused it?
I obtained it from a neighbor who has a huge and I mean huge San Pedro cactus out in the front yard , and we do live in a rainy area and that San Pedro has never suffered this problem....so I do not know...the other much older cactus are fine, with flower buds so I have no idea what happened to these San Pedros which got this rot.

Thanks
Cristina

My only thought is that you cut the rotting spots off each cactus and let the cuts air dry. But if you don't figure out what caused it in the first place, it will happen again.

Are only one size plant affected? Do the rotting sides face one direction? Is it the side the rain hits? Is it the side with the most sun?

I don't think its too much rain; more likely the yellowing spot is sunburn. San Pedro cactus don't have a lot of defences for handling direct sun (dense spine cover or wool). It would be best to move them to an area with light shade.

Happy holidays to you too Christina!

I agree with Daisy. I have had a problem on mine that looks just like yours in the past And I know it started with sunburn. Now I am super careful to keep it somewhat sheltered.

Bill

Thanks Daisy

Yep I do believe that your right, the sun could be the problem as I use to have the affected cactus in an area where it was partially shaded and now they were moved into direct morning sun maybe the change caused problems. The older ones were always in direct sunlight and they seem great, two have flower buds forming. I think I better keep an eye on them all....

As for the affected ones , seems that the wood ash worked , rot seems to have stopped and the San Pedros which I sliced up into sections seem to be ready to replant soon, will wait another couple of days and see how they are.

On the positive side, I will have more San Pedros to add to my collection.

Thanks Cristina

Great!

I had a similar problem with rot (or maybe it was breakage when the plant fell over. I took the tip, let it dry some and then put cinnamon powder on the wound and stuck it into expanded clay pellets. The pellet medium was dry. I started lightly watering it weeks later and now, about 6 months later, the tip is still solid and I expect it has roots. Anyone else try cinnamon?

Cinnamon is a natural fungicide. It is very commonly used by orchid enthusiasts - I hadn't thought of using it on cactus but, as it's a powder, it sounds really smart.

Daisy