Crop protection chemicals provide farmers with a cost-effective way of improving the yield and the quality of their crops. They also make harvesting more straightforward and maintain consistent yields from year to year. The main classes of crop protection chemicals are herbicides, insecticides and fungicides. Selective herbicides, for example, control the growth of weeds which would otherwise grow among a crop, competing with it for water, nutrients and sunlight. Without crop protection chemicals agriculture would be less efficient.
Research done over the past 20 years, mainly by Dr Erich-Christian Oerke and his colleagues at the University of Bonn in Germany, has shown that overall crop yields would be around half their current levels without the use of crop protection products. In certain crops, for example cotton, which can be spoilt by a host of different insects and competing weeds, the losses can be as high as 80 per cent.
For more you can check:-