Disease question

[Mike P]

Hi
First time I have encountered this. Photo is of a new segment from a darwini. The black spots started about two weeks ago and have now spread to cover the end. Other segments dispaly some spotting but not to same extent. I have seen similar on T. articulatus in the depths of winter but not on new growth in summer. Too much humidity?
[attachment 13365 darwini1.jpg]

[Mike P]

Second shot is after dissection. very soft black 'rot' which oozes slightly.
Thoughts?
[attachment 13366 darwini2.jpg]

[DaveW]

Had a similar thing on a Trichocereus some years ago. As you say it oozes pus. I never did find out exactly what it was, but I used a systemic fungicide on the plants and it seemed to stop it, though the affected bits had to be cut out.

It could be "Soft Rot" on this link:-

http://plantpathology.tamu.edu/Texlab/F ... cacti.html

Our plants often get stabbed with the neighbouring plants spines.

DaveW

[Stuart Estell]

The smaller ones are particularly prone to this - among opuntioids I've had it affect Tephrocactus articulatus most often, various small Maihueniopsis, and Corynopuntia invicta, etc. But I've also lost branches of Selenicereus to it occasionally.

In his book on Tephros, Michael Kießling reckons it's a form of botrytis. Either way, the only thing you can do really is chop the affected part off.

[Mike P]

Thanks Stuart. I will monitor the other segments carefully. Have you seen the problem in the summer before?
I may also try a spray with a fungicide.
How did you get your keyboard to produce the 'double s' for Kiessling?

[Stuart Estell]

Hold down the Alt key and then type 0223 on your numeric keypad, then release. There's a handy index of alt-key character codes [here]

Yes, I've had it at various times in the growing season - it's certainly not just a winter thing. It made a mess of my invicta slap bang in the middle of last summer.

[Mike P]

Stuart
Excellent link. A whole new world opens up to me......'Ai! laurië lantar lassi súrienen......' you learn something new every day.
Mike

[Diane]

This problem seems to be rather common in opuntioids, my hubby grows a few, and has encountered this quite often. He also had it on a cereoid, and I think he even took it to Wisley, who told him it was a fungal problem.

[Maria J]

I second that! Thanks Stuart!!