A potted Brown Turkey shows signs of rust after a late cold spell with temps just above freezing and high humidity two weeks ago. My figs are kept in a green house so I don't worry about cold temps, I also keep the frost out it with an electrical heater. So it really is the moist air that does it.
The question is, do I have to combat it (sorry for the word, I am a soldier...) or will it disappear when the air will get drier?
It is the only variety that shows this rust, all the others are perfect.

You can try a liquid copper fungicide but I usually just leave it as it is. Down here(high humidity all year) older leaves seem to get it eventually. It will not go away on its own, but he tree will just grow new leaves without rust.

And it will not spread to the other figs? I could move it outside by now, since the cold days are past now and we are having early summer days now.

Yes it will like napom! Get liquid copper i am combating it and taking it by storm. Spray it every 3 weeks. I live in south louisiana so i know about rust

Liquid copper is still for sale in Belgium, in other European countries is has been banned. On an overcast day it will probably be safe to use it. Thanks for the tip.

Hi Stormy,
If the humidity is in the greenhouse, why not just air the greenhouse more ?
I would too move the affected one to the outside - but rust makes spores and they are already probably everywhere in the greenhouse.
So venting the greenhouse more to lower the spores concentration would be my way to go.
Of course, on cold days, keep the greenhouse closed. Just vent on warmer days and between noon and 2PM ( hottest hours of the day normally) .

I have moved it outside, since the weather is real nice now. Finding the balance between keeping the warmth in and ventilating is not simple, especially with overcast weather. What is the best relative humidity for figs or better what is the highest acceptable level over a period of time?
Don't know if any figures exist on that.