Crop plants are an essential source of energy and raw materials that are used in the food chain. In the past, research was directed toward optimizing crop yields by genetic improvement, application of fertilizers, and the use of chemicals to control insects, nematodes, microorganisms, and weeds. For example, in America in 1950, one farmer produced food and fiber for 27 people; in 1990, the production was for 128 people. 1 This increased efficiency, however, has not come without costs. For instance, the U.S. Environmental Protection Agency has identified agriculture as the largest nonpoint source of water pollution with many of the polluting substances being pesticides and nitrates from fertilizers. 2 The question for the 1990s then is how we may improve the plant’s health, so that it may annually produce both economically and profitably without endangering the environment in the process of improvement.