To prevent insects and weeds from lessening crop yield. It also used residentially to improve the quality of lawns.
Many different foods, especially leafy green vegetables and fruits. Organic foods are grown without pesticides.
(1) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3761357/
(2) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4399309/
(3) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3648782/
(4) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1699233/
(5) https://www.ncbi.nlm.nih.gov/pubmed/15890768
(8) https://www.ncbi.nlm.nih.gov/pubmed/21126939