Two technologies of crop protection are compared, crop protection by pesticides and by Genetically Modified Plants (GMPs). The history of pesticides provides lessons relevant to the future of GMPs; (1) high pesticide usage is counter-productive, (2) the technology requires intensive regulation and (3) has nonetheless many external effects which strongly reduce its social benefits, (4) early calculations on net benefits of pesticides were over-optimistic, and (5) intensive use of pesticides made farmers so dependent on them that they lost important options. These lessons are used to construct a framework for the economic analysis of GMPs which can be applied once sufficient empirical information becomes available. Conceptually the framework can be used for a comparison of crop protection strategies indicated as chemical crop protection, threshold-based crop protection, crop protection by ecotechnology and organic agriculture. Given the current state of knowledge on the impact of GMPs where (1) benefits are assumed rather than proven, (2) regulatory costs are rising and (3) environmental and human health risks have yet to be fully identified, one conclusion is that ex ante economic analysis which draws upon some of the lessons learned with chemical pesticides may help to bridge the gap between the proponents and the opponents of GMT (Genetic Modification Technology).