I just saw your post and know the problem; as I am experiencing a similar problem; I have had a nursery person look at my tree. This happens to Fig trees (and other trees) and it is called Rust. It happens when the leaves get wet (from constant rain -or when watering the tree; you don't just aim at the roots; but water the leaves also. The problem occurs when the leaves don't dry out before they are we again. If you don't remove the leaves when you first see yellow spotted leaves -or black if it has been on the tree more than a few days; they will fall off of the tree; as well as they will affect the other leaves.
If it only happens, say last year; you can remove the affected leaves -once they start turning yellow; they will turn black/brown. Make sure that you don't burn the leaves, and pick them up if they fall on the ground. And put them in a bag; then in the garbage.
My Fig tree had Leaf Rust last year; and this year it was fine until the middle of Summer (actually last week). My advice from the nurseryman is this: Remove all affected leaves -it took ages and me on a step stool to get them all. Then dispose of them. After that, you need to spray with a Fungicide. I bought an inexpensive 1 gallon sprayer; and was directed toward, "Liquid Copper Fungicide." The copper is an ingredient that helps kill the rust. It states to spray and "hope" that it is not going to rain for a few days afterwards. Currently, my FIg tree looks good since I have removed all of the affected leaves; but I haven't been able to spray. We have had rain everyday for at least a week; and it is calling for rains again today. The rain will wash all of the fungicide off and the spores/rust will grow back since the treatment wasn't able to take.
I need to talk with my nursery friend. Part of me wants to go ahead and spray -since I know that it will rain today; I don't want to waste the money on the fungicide and have it washed off of the tree. Thunderstorms are called for through Sunday. They don't start until 4:00 PM (predicted) today; but that isn't long for the spray to penetrate and not wash off -it is 10:567 AM here now.
I haven't checked the weather where you are located; however, if you have/have had rain, but it isn't raining now, you can go remove all of the affected leaves (even those with yellow spots on them -that's how it starts); and if you can spray without the rain coming; go to Home Depot (or other places where you can buy it); get a Fungicide and spray the tree well -under and on top of the leaves; and the area immediately around the tree; in case some of the fungus got on the ground from the leaves falling.
I hope that this helps. I know from experience how stressful this is. Let me know how things go for you in getting your tree free of the rust.
