Farmers know that weeds will be a problem every year and weed control, including the use of herbicides, is built into the regular farming routine, regardless of farm earnings. Continual herbicide use can lead to problems with weeds developing tolerance to some herbicides. Insecticides Insect infestations may alter crop growth and cause enormous damage and destruction of the crop. Responsible use of insecticides is usually necessary to control insect pests, but relying only on chemical controls can create problems because such practices can cause resistance of the pest to the chemical, destruction of a pest's natural enemies, increase secondary pests to problem levels, possible environmental contamination, potential health hazards, and negative public attitude. The decision to use a pesticide depends on the cost of the chemical and application compared to the value of the crop loss and damage if a pesticide is not used.
Insecticides are less widely used in Canada than herbicides.
This is because they are not applied routinely, often only when monitoring shows that a pest has reached a certain population level. In contrast, insecticide use is low on land cropped to wheat and oilseeds. In the Prairies, insecticides are generally used only when seeding, tillage and rotation practices have not successfully controlled an insect problem and when the cost of applying the insecticide is offset by the potential economic loss due to insect damage of the crop. Insecticide treatment of the soil is often too expensive for grain crops and is reserved for crops that give higher returns per hectare, like potatoes.