Pesticides are chemical or biological substances that are used to kill or control pests that harm our food, health or environment. They are particularly used in food production because pests can have devastating effects on the quantity and quality of crops. Pests include rodents, insects, fungi and plants. Only officially approved pesticides may be used. Plant growth regulators, which are used to influence particular growth processes in plants (for example, slowing down the growth of sprouts on potatoes) are also regulated as pesticides.