Yes on the ground. Or you can get hand held spreaders that will puff it out like a cloud of dust and spread it on leaves to take care of aphids and other leaf munchers and such.
Diotamacious Earth (DE) is one of the easiest pesticides to use under leaves where most people don't bother to look for pest infestation.
Best application is in a duster, as it can reach under leaves , and whatever falls to the ground will continue to protect plants on the soil surface.
It is a "two-fer, freebie ".