In a context of rationalised agriculture integrating the principles of sustainable development, preventive measures for crop protection are called upon to play a dominant role. These preventive measures are based on close knowledge of the functioning of agroecosystems. They are aimed at managing biological pests and their natural enemies, first through action on their habitats both in crop fields and in the non-cultivated part of the farm. A balance of the biological control possibilities available is drawn up and attention paid to the application of recent knowledge in conservation biology. The bases of pest control with a ranking of the various intervention techniques are then set out. Implementation means the development of cropping systems and therefore increased participation by agronomists and also a break with certain agronomic practices commonly used by farmers today.