Sure, no more bees would be a very, very bad news. But humans are a pretty hardy specie. First, we are omnivores. Second, we have conquered the whole planet and live in huge numbers. And third, we are really smart. Besides cosmic scale events, I don't think of many scenarios that could damage humanity beyond recovery.
The authors of the FAO analysis concluded that the proportion of global food production
attributable to animal pollination ranges from 5% in industrialized nations to 8% in the developing world.
That being said: it is pretty hard to predict waht would happen suppose there were no bees at all. I doubt it would be nice though.It _may_ not be caused by the pesticide, changing or stopping the use of the pesticide could not be necessary and then we would have accidentally saved the world while having less profit.
How do you know this? Because of the possibility (and it will always exist) of something else able to harm bees we should take no action?
> "we don't know how to save all the bees"
Is this forgone conclusion? Sounds like you are begging the question [1]
I am reminded of, http://i.imgur.com/couhw4k.jpg
Edit: I definitely didn't say that we should take no action.
Edit2: If you're asking "what else has been killing bees en masse", here's a list: https://en.wikipedia.org/wiki/Colony_collapse_disorder
When they are gone, so are we.
Bigger, more profitable yeilds is not what we should be focusing on. Saving the bees and humanity in the process is slightly more important imho