Diatomaceous Earth - made of tiny, aquatic organisms called diatoms. Their skeletons are made of a natural substance called silica. Diatoms accumulate in the sediment of rivers, streams, lakes, and oceans. Diatomaceous Earth provides many benefits in the garden with silica for plant growth, but also for pest management as DE is dehydrating to aphids and other sap sucking insects. DE does not harm worms or beneficial microbes in the soil, but it will your lungs, so use precautions. Please see pesticide label here. EPA reg. 50932-12.