Diatomaceous Earth- Food Grade What insects can DE be used for? adult flea beetles, sawfly, coddling moth, twig borer, thrips, mites, cockroach, slugs, snails and many other insects such as: Aphids, thrips, earwigs, silverfish, and ants. cabbage root flies, carrot root flies, fleas, pillbugs, ticks and is helpful in dealing with fungus gnats. stoves, cabinets, sinks, garbage cans, drains, and in cracks and crevices. Repeat treatment as needed.