i just bought this little tray of cacti--- and they all have mealy bugs on their roots! i've searched the forums for info on how to deal with this but i would like a little clarification. i read that submerging the pots in a bucket of horticultural oil would do the trick, but how does it work? does it kill the mealy bugs? is it dangerous for cacti? how long should i leave them submerged and do i need to water them to flush out the oil afterward? do i use pure horticultural oil? that's a lot of questions, i know, but i'd appreciate any help you guys can give me. these little cacti are really sweet! thanks!