The introduction of synthetic pesticides (insecticides, fungicides and herbicides) changed the outlook on pest control as part of agricultural intensification. Heavy reliance on such compounds has only developed since the '40s. The present annual value of pesticide sales is about US$ 25 to 30 billion. Pesticide use remains highest in developed countries but these markets are stagnating or contracting. Environmental concerns have become overwhelming and in several countries, programmes have been established to reduce pesticide use.

• farmers have been instructed to use pesticides as a necessary component of "modern" agriculture
   
• pesticides are often used with no relations to real field needs (on a calendar basis, or insecticides on a fungal infection)

In developing countries, during the green revolution, pesticides were considered a necessary part of crop intensification. A number of policy instruments were applied to make purchased inputs, including subsidized pesticides, available to the farmer. Pesticides also became part of loan packages and extension messages. This often resulted in a substantial mis- and over-use of pesticides. Such methods of plant protection have proven to be increasingly unsustainable and cost-ineffective due to the development of pest resistance, the rising costs of pesticide use, pesticide-induced outbreaks of insect pests and the negative effects of pesticide use on human health and the environment.

Indiscriminate use of pesticides has resulted in changes in plant protection strategies. Since the mid 1960s, Integrated Pest Management has been advocated by FAO as the preferred pest control strategy. Integrated Pest Management is the careful integration of a number of available pest control techniques that discourage the development of pest populations and keep pesticides and other interventions to levels that are economically justified and safe for human health and the environment. IPM emphasizes the growth of a healthy crop with the least possible disruption of agro-ecosystems, thereby encouraging natural pest control mechanisms.