you use the turn undead ability to turn vermin (basically your turn undead was given a dual function by plant domain.)
Vermin:
"These creatures operate on instinct, driven by simple needs such as food and reproduction. Except where noted, vermin attack only when hungry or threatened.
Vermin Traits: Vermin possess the following traits (unless otherwise noted in a creature’s entry).
—Mindless: No Intelligence score, and immunity to all mind-affecting effects (charms, compulsions, phantasms, patterns, and morale effects).
—Darkvision out to 60 feet.
—Alignment: Always neutral. Vermin are not governed by a human sense of morality.
—Treasure: Vermin generally possess no treasure. For those that do, this treasure consists of possessions formerly owned by a creature that the monster has killed."
Vermin include:
Spiders (barring ones that are magical beasts such as Aranea, hallow wraith spiders i think, and bebliths that are demons not spiders.)
Beetles (stag beetles, fire beetles, bombadier beetles)
Ants
Mosquitos (mosquito swarms should be vermin I believe)
Wasps
Can't think of any more... and I think formians are probably... monstrous humanoids.