In this article, we use the term to refer to material found in nature that is minimally altered by humans and not likely to be harmful to you or your garden. Most natural pesticides are the desirable choice because they are nontoxic to humans, other mammals, and nontarget organisms, and are specific to the few insect pests for which you might want to use them. They can be derived from microbes or from plants and should be handled with the same safety precautions you would use with any other pesticide.
Microbial diseases kill insects much the way they do humans.
The pathogens that cause these diseases often affect only a specific host, or group of insects, and don't attack others. The Bt products sold in stores are commercial formulations of the naturally occurring microbial organism. The organism has been taken directly from the wild and is not genetically altered by humans. Most of the formulations you will find for retail sale indicate they contain Bacillus thuringiensis var. This strain is limited to controlling certain caterpillars.