Disease identification help

[grossetti]

Hi everyone,

I have something strange happening with one of my oldest (+26 years) cacti, an Opuntia Engelmannii. I had a look in the disease identification page but I cannot find something that resembles this, please see the picture. Some info:

it does not look like mold, the white part is dry and hard. As you can see sap comes out sometimes. I first thought something was biting my cactus but I am not sure about this anymore. Any help as greatly appreciated!

Thanks,
Gabriel

[DaveW]

Coincidentally one of my BCSS Branch members asked me the same thing today. It is just normal aging of the plant known as corking, meaning as that tissue stops photosynthesizing it forms a bark rather like a tree trunk. See:-

http://www.desertplantsofavalon.com/nat ... nt-plants/" onclick="window.open(this.href);return false;

Often slow growth in cooler climates will cork earlier than for you in warmer climates where the plants grow more actively.

[grossetti]

Hi Dave,

thanks for the reply.

I know about corking, it has happened below (the brown colored parts). This however looks very different, it is happening in young pads (0.5-1 year old) as opposed to the older parts below. It also seems to spread randomly, I cut off the youngest parts because they were quite hit by this and I was afraid it was a fungus spreading. The pads I cut off had lots of sap that had leached out, like you can see in the pad closest to us in the picture, but a lot more. I would like to mention that this started occuring in the summer, about a month or two ago, not earlier.

I have never seen this on any cactus before.

Thanks,
Gabriel

[DaveW]

They may have got sunburnt then. particularly as you say it started in summer. Sometimes it appears as whitish patches and sometimes as brown depending how severe the burn it. I have even had plants sunburn in my greenhouse in the UK with the bubble wrap plastic insulation still up. Often inside a greenhouse it is exacerbated by lack of ventilation and free air movement. With plants in pots it can also occur if the side usually facing the sun is turned so the shady side is now in full sun.

https://desertxeriscape.wordpress.com/2 ... -like-sun/" onclick="window.open(this.href);return false;

http://www.cactusmuseum.com/photoinfo.asp?PhotoID=10" onclick="window.open(this.href);return false;

[grossetti]

Ok, maybe this is it. This cactus always stays outside (no greenhouse for him), I only wrap it up for winter with a special cover that's used for palm tree tops. I unwrapped it in March though so it gets used to the sun so it doesn't sunburn. These white patches occured on new pads and on older pads and not in a place that gets much sun shine so that worries me it is something else. Also I have never seen sunburns "bleed" sap but I haven't seen everything yet I guess. I hope it is just a sunburn.

I will keep on informing everyone of any changes and if anyone else has any ideas it is much apreciated!

Thanks,
Gabriel

[thomas]

On the pads that you cut off did you by any chance bisect them to see if something was in the infected area like a worm or boring insect? Not sure if a fungus would cause that sort of bleeding but a boring insect of some sort would. Could you post a better close up of the infected area?

[grossetti]

Hi,

no, I will cut another one off soon and do this. I uploaded two close-up pictures of this "thing" and one of the natural corking the base of this cactus has, to show how different it is.

Thanks,
Gabriel

[grossetti]

Ok, so I have new picture, as you can see, by comparing one of them with the last batch, this thing has grown. Plus I noticed part of it resembles a big bubble, like an infection on a human. I rubbed off the white film and you can better see the bubble. I still have not had time to operate, I think I will open up the bubble first...

any ideas?

[grossetti]

So, I finally had time to dissect the spot and bump, and it doesn't look good. I cut around the bump and "puss" came out (for the lack of a better word). I removed the had grey skin and the flesh has the consistency of baby fruit puree. I was able to scrape and cut it all off. On some pads, it looks like the "infection" is no longer spreading, this is only where the grey spot was less than 2cm around, it looks like the grey skin is pealing off. It may be that the cactus is able to fight it off it it is not too big, this wasn't the case with this big patch though, it kept on growing. I attached some pictures of the "operation".

If anyone has an idea what this is, please share.

Thanks,
Gabriel