ABSTRACT
Control of crop parasites is felt to be indispensabile to maintain and increase the level of agricultural production and to combat hunger in the World. The number of phytophages which attacked citrus fruit up to immediately after the second World War was relatively small and the damage, which was very largely due to certain scales, was relatively unimportant, being efficiently controlled by inorganic means of control made up of polysulphides, which were soon replaced by synthetic chlorides, phosphorganics and mineral oils and oils of organic origin (nicotine), which were also efficient against aphids, while prussic acid was widely used to combat the scales infestations. It was also found that the antiparasite treatments constituted a danger to man and to animals, in the form of acute and chronic poisoning, which occurred after the biological balance in nature between phytophages and their parasites and predators was upset.
