I'm in the process of bringing a lot of my cacti inside from my little greenhouse just for the next four months or so. (I'm in the UK and its getting cold). I have three ferocacti, and I noticed that the spines were much paler than usual. On further inspection I also noticed a sooty mould on the furry areoles. I haven't been able to get on here for three days so have been worried as what to do? Can anyone give me opinions on these! I don't want to lose them
I don't think the mold will hurt the plants, it's just unsightly. Moving them to a less humid environment well probably stop its spread, you could spray with a fungicide to be sure.
Difficultu to control. The areoles produce nectar and then it goes mouldy. The only real solution is to remove the nectar before it can go mouldy. A sufficient number of ants can do this, or a sufficient amount of rain. In very hot dry conditions it can dry out before there are problems, but in the UK it may just go mouldy later when it is damp again. It is a pain to wash off once it goes black but it can be done.
I've never seen sooty mould cause serious problems to the plant.
My area is overrun with tiny black moisture ants, which get into everything - undoubtedly why I've never had this problem despite our damp climate. The even started a nest under my F. pilosus at one point - while this wouldn't hurt the plant I wasn't happy about it, breaking up the nest and moving the plant convinced them to go elsewhere.
