Hi,

Is your tree in a pot, or in the ground? Have you recently fertilized it? Does it have good drainage?

I hope someone here can help you with this problem,

noss

If it is in a container, it may need water. I missed a couple of days with a potted one and some leaves turned yellow and dropped off. Drenching it reversed the situation.

I'll second the "lack of water" explaination. I just asked a similar question about my potted fig and when I got the "lack of water" answer, it all made sense.....2 weeks prior I had droopy leaves before I watered it. A week ago I had major yellowy leaves. Things are much better now, but I'm chalking it up to a lack of water.