It is necessary to study pests with a new reading of life history traits, multitrophic interactions within agro-ecosystems, and farmers' practices.

Knowledge of pests is founded on population dynamics. These basics must be supplemented with an understanding of the interactions between species in order to develop new agro-ecological crop protection practices so as to cope with new challenges: acquisition of multiple forms of pesticide resistance or enlargement of the ecological niche, biological invasions, etc. Although weeds generally have an indirect impact on crops (competition for resources), unlike pests, they are also seen as bio-invaders. This work centres on weeds and insects in tree crop systems (mango) or annual crop systems (market gardening, lowlands, cotton).