Question
i have a large rubber plant outdoors in a container - we live in south texas.  about 20% of the leaves develop yellowish spots that gradually get larger turning to brown which curls up the leaf until it eventually falls off.

any idea what this is and how to treat it?

Answer
Hi Bob, we (South Florida here) are in winter now, as you are, and the colder nights is stressing our tropical plants; its a normal transition and most plants adjust, what happens many times is fungal problems set in. From what you have described, I think this is what is happening to your Rubber tree, they are very sensitive to climatic changes, heat, cold, rain etc. There isn't really anything for you to do but wait for it to adjust, the leaves that are shed should be cleaned up, and it should run its course. Watch the watering of this plant this time of year, too much water will exacerbate the situation. Nick