Diatomaceous Earth (DE) is a natural garden pesticide that is composed from the diatomic fossils of prehistoric beings. This product is labeled as food grade but for your precaution, should be used on plants, garden and terrariums only, and should not be directly consumed.
How does DE work against pests? When DE is dry, its structure is very sharp and once pests get in touch with it, it acts like miniature blades on the respiratory system of the bugs. Apart from that, the mucous memberances and the lungs of the bugs dry out. The particles of DE, however, are so tiny that is it safe to use aroud humans (including children), wildlife and pets. But it is best to use a mask while applying it if you happen to have any know respiratory problems (eg: asthma).
Which pests is Diatomaceous Earth affective against? Pretty much all. But it is especially affective against thrips, mealybugs and fungus gnats, as they tend to lay their eggs or are in the soil at some point during their life cycle. But DE is also effective against slugs, beetles, worms, fleas and spider mites.
How to use DE? For fungus gnats, thrips and mealybugs, apply DE by sprinkling on top of the soil about 2 days after you have watered the plant. Make sure your hands are fully dry before touching the fine powder. Re-apply about one time per week 2 days after watering the plant again. You can also sprinkle the DE dust on any plant by covering the top, the undersides of the leaves as well as the stems. Just make sure to reapply it after rainfall. You can also mix DE into your potting mix but bear in mind that once it is wet, it will lose it’s pest-defending abilities.
Hence, IMPORTANT: when you apply DE, the soil or the plant need to be DRY.
How much Diatomaceous Earth do you need? For application on top of the soil, you need about 5ml (about a teaspoon) to fully cover a 14cm pot.