I know that Datura is host to the larva (caterpiller) of the hawk moth.
These larvae are large and should be obvious on the plant. While the
larvae will denude the plant (eating whole leaves and leaving only the
midrib), rarely does it outrightly kill the plant. Often there is a
flush of new growth after an infestation. The hawk moths are important
pollinator of flowers that open at dusk. The moths are the size of
small hummingbirds and have tongues longer than their bodies. They are
If this is your only Datura, you can use a bacillus thuringerensis
(sp.?) known commonly as BT. The larva ingests the bacillus and dies
within hours. It comes in powder and liquid forms and is not harmful to
human (considered an organic solution).