You might have psyllids, and those "salt like' grains are what is known as psyllid sugar.

Rather than copy and paste or retype info, I've linked to an older GardenWeb thread about psyllids.

Hopefully that is not what the issue is or if it is, you can get it under control quickly.

Betsy

Here is a link that might be useful: Thread about psyllids

Thanks for the link. I touched the white grains, it's sticky and there are several psyllid on the picture too.