Today, there are many categories of chemical pesticides being used in Canada, of which five principal classes are discussed in this chapter. Those in the organochlorines group were first used in the 1940s. From about 1945 to 1965, organochlorines were used extensively in all aspects of agriculture and forestry, in protecting wooden buildings and protecting humans from a wide variety of insect pests. The discovery of a second more powerful group of insecticides, the organophosphates , led to the replacement of organochlorines and, in fact, many organchlorines are now banned in Canada 16 . The word pesticide is more specific and includes herbicides, insecticides and fungicides, as well as algicides, insect and animal repellents, antimicrobial and cleaning products, wood and material preservatives, and insect and rodent traps.
Most pesticides are intentionally toxic to the target organisms.
These, too, can be harmful to human health or the environment. 3.3 Carbamate insecticides came into use later than both the organochlorines and the organophosphates and are less widely used than the others. The synthetic pyrethroid group of insecticides was introduced more recently, in the early 1970s, although natural source pyrethrum has been used for hundreds of years. Synthetic pyrethroids are more stable to light and possess a higher insecticidal activity, almost ten times that of most organophosphates and carbamate insecticides. The stability and activity of the synthetic pyrethroids are reflected in their increased use during the last two decades on fruits, vegetables and corn.