IC wont work as well .. insect plague 'll keep folowing Irenicus, and keep interrupting his spellcasting even if he jumps after that ( he will ).
But hey, as a complimentary spell, why not [img]tongue.gif[/img]
Just prepare for a long fight, 'cause it takes a while for the insect plague to reach irenicus .. and make sure his protections are down by then.
It's all about stopping him from casting healing-spells the second he teleports away.
If the spell gets absorbed by his spell-turning or whatever, make one of your own summons near him hostile ( use a weak summon
)and fire the insect plague at him .. indirect insect plague's wont be stopped by spell turning IIRC.
go get him [img]tongue.gif[/img]