‘Cide’ as a suffix that designates something to be killed. ‘Insecticide’ kills insects. ‘Miticide’ kills mites. ‘Molluscicide’ kills molluscs such as snails and slugs. ‘Herbicide’ kills herbaceous plants, which are presumably weeds. These examples and other chemicals that kill things that are considered to be pests are collectively known as ‘pesticides’. Many are potentially useful in the garden, since that is where so many familiar pests are problematic.
Most modern pesticides are designed for physiological characteristics that are unique to the targeted pest. They therefore kill only very specific pests, but are generally harmless to other organisms. For example, horticultural oil, which is one of the simplest of all insecticides and miticides, kills insects and mites by obstructing the exoskeletal pores through which they respire. It is harmless to those of us who conduct respiration by means of lungs.
In fact, most (although not all) commonly available pesticides, if used…