what's wrong with my Flava??

[jop_pk]

i bought this flava on 30 jan 2009 and repotted this flava on the same day i didn't disturb its root at all. old pot was full of root.. so tight as i hardly saw medium. I just put it in bigger pot and add more medium. it looked fine for me for now it's about 2 months. problem came just a few day before..
anyway today i noticed some small white insect.. very tiny ones around below rhizome area. not sure if it's mealy bug.. they don't stay at same spot. so i spray (...some kinda pest killer for plant... don't know how to explain in eng. (S85) it worked well with my sundew before. ) after spraying they run up all over.. i saw them around 10-15 .. not sure if those small insects cause this problem..
and one more problem .. after i spray my plant for an hour later. i put my plant outside almost full sun with little shade.. and water tray just about 2 inches.. a couple hours later lucky i'm at home today. my plant seemed to be dehidrating.. i moved it in shade and water it from top for a few times .. not sure it was about pest killer.. after that it look better but some leaf remain wilther.
i hope my plant will be ok.. it's really expensive for me 1800 Baht .. it's really big flava..
any idea to avoid this pest? my plant's gonna be allright?
thank you very much for ur help