Organic food covers a wide variety of techniques and different types of foods that all have their own types of legal loop-holes, or possible work-aroundsaround strategies.
In response to the scares involved with pesticides in general, people began to research methods to minimize the amount of pesticide used. Basically, DNA from an external source is inserted into a plant so that the plant inherits some desirable traits. This allowed plants to develop natural immunities to certain bacteriasbacteria and produce more or bigger produce. Over time, people became scared of GMOs as too good to be true. For the most part, scientists agree that GMOs pose no greater risk than conventional food (Expert evaluations from Europe found no verifiable toxic or deleterious effects from GM foods and crops). There are still legitimate concerns about using GMOs, such as allergy development in humans, toxicity levels of naturally produced pesticides in the plant, and antibiotic resistance of bacteria, but for the most part these are tested before distribution. Public wariness may be influenced by labels and commercialism.
http://people.oregonstate.edu/~muirp/pesthist.htmOregon State - History of Pesticide Use
http://www.toxipedia.org/display/toxipedia/DDTToxipedia - DDT