Answer: (((oooohhh edit edit! Far too catastophic! Soften it out!)))
Unfortunately, a lot of the homemade and "organic" pest and disease controls available are harmful to more than the target pest. The benefit of these is 1) ready availability of the ingredients and 2) they break down relatively quickly in the environment, so their effects don't linger long. Soaps coat soft-bodied insects and dissolve their outer skin, and can interfere with the movements of other non-target insects. Some soaps contain detergents that can harm plant tissues. In tobacco, the toxic ingredient is nicotine, which is is deadly to all insects and animals (including humans!) in high concentrations.
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