It may be safer to those plants to shake them and vacuum underneath to catch any insects that fall. Diatomaceous Earth Diatomaceous earth is composed of finely ground skeletons of fossil diatoms. Sharp edges of the ground diatoms scratch the waxy or oily outer layer of soft-bodied insects, which reportedly die eventually from dehydration. Because it functions to scratch the insect's outer body covering, diatomaceous earth is categorized as a mechanical pest control. However, it may also be considered a mechanical barrier or repellent because some insects will not crawl on or feed upon plant foliage sprinkled with it.
Diatomaceous earth is a dusty product that looks similar to flour.
There are various formulations, including one sold for swimming pool filters, which does not help control insects because it has been altered by high heat to make it a stable filter material rather than an absorber of insect oils. Before buying or applying diatomaceous earth, gardeners should read the label and look for the insect control formulation, since some brands are not labeled for vegetables. It is considered a pesticide, but it is non-toxic to birds and mammals. On the other hand, diatomaceous earth can be a disadvantage because it may also kill beneficials such as ladybugs, and it is less effective against pests in humid weather. Gardeners must wear a dust mask when applying diatomaceous earth to plants.