Pesticidal plants, also referred to as botanical pesticides, have been used for centuries for pest management. Evidence of their use in agriculture dates back to Greek, Roman and Egyptian empires. They were the main method of crop pest management in modern times until the development of synthetic pesticides in the mid-twentieth century. Synthetic pesticides were designed to overcome many of the problems with natural plant products, i.e. to be more stable and resist breakdown by sunlight and to be generally fast acting. Although synthetic pesticides can work very well, overuse and misuse of synthetics has led to considerable human and environmental health problems. This calls for a shift in pest management towards practices that are more sustainable and based on sound agroecological principles.