DE is very safe, but you want to get the kind for gardening, not the kind used in pool filters. That is a problem variety. There is a brand that comes in a bottle with a long straw you poke into the end (kind of looks like a huge hypodermic) and puff it onto the plants.

Soil Mender crawling insect killer is the brand and type. This type of DE is commonly used in animal feed. You just don't want to go inhaling a huge gob of it. (You don't want to inhale a gob of ANY powder, though!)

SRS