never had this as a problem but I guess a general fungicide should work. you'll know to destroy any affected leaves and not compost them at home.

I understand it is prevalent in warm moist conditions, and from what I have read the best way to prevent it is by cutting off and destroying the leaves as it develops.
I have had the problem and I try to make sure I don't leave any decaying leaves lying on the ground, so I cut them off when they develop the spots.

It is also advisable to grow the plants where there is sufficient ventilation/air circulation around them.

I believe an 'ordinary' fungicide is also helpful.

Thank you both. We do have a lot of problems here with fungus, and I guess its because I overcrowd my plants, combined with our damp summers. Thank you. I shall remove the leaves sooner in future. I don’t make compost.

Happens every year here. I only remove them when the spots begin to show in the autumn.

Karen, at this point of the season I would snip off and discard the infected leaves as the plant is shutting down for the season and doesn't have much energy now. However, 3 percent hydrogen peroxide is an excellent fungicide. It's cheap and it works. It won't harm the plant or the environment. I use it as a mouth rinse when brushing my teeth. It has antiseptic properties.

It's so difficult if you are a plant person, to have much if any room around your plants. Same problem here.

I can't see any reason for trying to save the leaves at this time of year because in another few months there will be a nice big crop of new ones and the old ones will die anyway. At least they do here. But removing all the old ones will co towards avoiding any spores being left on the ground to reinfect next year.

Thank you. I have removed all the old leaves, so hopefully I can get on top of it next time it happens. Bathgate, how do you get 3% Hydrogen Peroxide?

Karen: You can pick it up at the supermarket - go to the personal care aisle, also any pharmacy or beauty shop would have it also. A bottle cost me about $1.00. You'll also find many many uses for it around the house.

Thanks Bathgate. :)