Every year, farmers have to struggle against the forces that attack crops and animals, that is, weeds, diseases and insects, which can all significantly reduce the yield.
The first line of defence against these enemies is to use appropriate farming methods, such as rotating crops and planting resistant varieties. Chemical pesticides are generally used only when a threshold is reached in economic terms: the value of the yield that would otherwise be lost balances or outweighs the cost of applying the product. In Manitoba, more herbicides are used than insecticides and fungicides.