Protection of crops from pests and from ravenous animals was long accomplished with the use of 'natural' means, before the introduction of 'modern' synthetic chemicals as pesticides in the twentieth century. The widespread use of synthetic organic chemicals as pesticides in the last several decades has contributed to the 'background' contamination of all environmental and biological compartments with trace amounts of small organic compounds, the combined effect of which on the health of humans and on the general well-being of complex ecological systems is far from being understood. In particular, it is claimed that the presence of trace amounts of such compounds in human food may contribute to impair the health of sensitive individuals, especially in the developmental and early-age stages of life, although there is not a clear-cut consensus on this problem. The request from consumers, mainly in developed Western countries, of food produced under perceived healthier conditions than those of mass-production, has prompted a backslash of interest in traditional, lower-yield techniques such as 'organic farming' and thus the necessity to protect consumers from unsubstantiated claims of food quality through the issuing of voluntary codes by producers and of guidelines such as Codex Alimentarius at the level of international Organizations. Another driving force into a renaissance of 'traditional' farming techniques is understanding that they can be successfully merged to 'modern' ones to achieve better productions with lower environmental impact, lower consumption of selective but expensive Plant Protection Products, lower contamination of food with residues. Another trigger to seek alternatives to the conventional means of pest fighting is acknowledgement that later generations may develop resistance to current pesticides in a continuous 'chemical war' between human scientific intellect and natural evolution of organisms. Traditional agricultural wisdom long recognized the power of coenobioses and used co-cultivation of different crops as a means to deter parasites by exploiting the natural emission of insect repellents and mutual fight between natural hosts of crops and invading organisms. Of course, since even 'natural' substances long employed to fight parasites of plants and food are intrinsically toxic not only to target species but also to several others, including the human, risk assessment of their use is mandatory to fully benefit of their strength without unnecessary risk for producers, consumers and the global environment. The recent exploitation of natural as well as of engineered organisms and of their toxic products as pesticides is another means the reach and limitations of which need to be fully understood. Examples of how these seemingly conflicting requirements have been or can be harmonized will be presented and discussed.