Since the time that Homo sapiens took up farming, a battle has been waged against pests and diseases which can cause significant losses in crop yield and threaten a sustainable food supply. Initially, early control techniques included religious practices or folk magic, hand removal of weeds and insects, and “chemical” techniques such as smokes, easily available minerals, oils and plant extracts known to have pesticidal activity. But it was not until the early twentieth century that real progress was made when a large number of compounds became available for testing as pesticides due to the upsurge in organic chemistry. The period after the 1940s saw the introduction of important families of chemicals, such as the phenoxy acid herbicides, the organochlorine insecticides and the dithiocarbamate fungicides. The introduction of new pesticides led to significant yield increases, but concern arose over their possible negative effects on human health and the environment. In time, resistance started to occur, making these pesticides less effective. This led agrochemical companies putting in place research looking for new modes of action and giving less toxic and more environmentally friendly products. These research programmes gave rise to new pesticide families, such as the sulfonylurea herbicides, the strobilurin fungicides and the neonicotinoid insecticide classes.