figs4me - You do not say what stage your RdB is; cutting, young tree, established tree, etc. There is a possible solution: aspirin. I agree with Gorgi and the others that FMV and the other viruses that cause fig mottling disease (FMD) are not currently curable in an established tree. However, by activating your tree's innate immune system you may be able to lower the viral impact and allow it to out grow its problem. Some of this was discussed in this thread:
http://figs4funforum.websitetoolbox.com/post/Instant-FMV-6004031
I had one of 3 Sicilian Black Italian cuttings start showing pretty significant FMD back in early August. Its growth seemed to stop while all my other cuttings were putting out new growth & looking happy. I do a foliar spray with worm casting tea and aspirin on my tomatoes every week or so. So, I have sprayed my FMD impacted cutting every week for the last 5 weeks. The established leaves greened-up, the mottling decreased in the established leaves, and it has resumed putting out new growth. As we say in science, this is an N=1 observation. I can not say whether the reversal of the FMD is due to the aspirin, the worm casting tea or the combination. It could be something else entirely. However, the results are consistent with the legion of reports in the literature on the impact of treating virally infected plants with salicylic acid.
There is a LOT still to be learned about FMD.