Answer: This is a difficult question to answer. Even the "safest" pesticides can cause harm if used improperly. Pesticide labels are legal documents, and it is illegal to do anything counter to what the label instructs.
Here is the web site for the National Pesticide Telecommunications Network. It contains a great deal of information about pesticides of all types.
Here is a .pdf file from that site with information about "signal" words used on pesticide labels--for example, what's the difference between "caution", "warning", and "danger".
Pesticides labeled as "organic" or "natural" are usually derived from plants or minerals. However, this does NOT mean that they are harmless. Some "organic" pesticides are, for example, very toxic to fish. You might contact your local Organic Farmers Association for more info on organically-approved pesticides.
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