Ferocactus black mould

[EdMcKenna]

Any suggestions on dealing with black mould on my Ferocactus horrida v.brevispinus.
I have two, the one on the right seems unaffected.

[jerryb23]

I use a small stiff artist paint brush with some neat washing up liquid and then rinse through with a fine hose jet. I find this works well with stiff spined Fero's.

In the past I have found that ants will do good clean up job but this takes time and obliging ants!

[Stuart]

Not really a suggestion for dealing with it but to stop it happening again, by watering overhead, it washes off the clear sticky 'nectar' before it has a chance to turn to black mould.

Stuart

[EdMcKenna]

I've seen some of my Opuntias secreting sap bun not any Ferros, this one came like that. I'll try a gentle brushing to see if I can remove the discolouration.
Thanks for the replies.

[guthrie]

*Makes note to keep an eye on his own ferrocacti for such a problem*

[Stuart]

The fancy term is 'extrafloral nectaries' which produce nectar which is mainly sugar to attract ants. In habitat, the ants swarm all over the plant for the sugar, the plant benefits from the protection the ants provide from less friendly bugs. The ants may well help seed dispersal also. In the greenhouse the nectar can be dissolved by regular overhead watering but unless washed away, it soon forms a black mould, not sure if there is any harm in this though it doesn't look very nice.

Stuart

[EdMcKenna]

Thanks for the information, I will have to keep an eye out for any signs of nectar production. I'm wondering if it's season specific as I noticed it last year on a large Opuntia in October. This made me bring it out of the greenhouse and overwinter it in the house. I was concerned that the damp and humid weather in October an November would make it worse. As I said it was on this Ferocactus when I bought it and I haven't seen any further signs.
I will keep an eye out on this and my other Feros and Opuntias.