Home: About Pesticides

From: The Standing Committee on Environment and Sustainable Development, House of Commons, Canada

There is information to suggest that certain types of pest control products were used in Roman times, but the use of synthetics began in the 1930s and became more widespread after the end of World War II. Today, there are many categories of chemical pesticides being used in Canada, of which five principal classes are discussed here. 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 (Environment Canada Web Site, 1999). Certain organophosphates are systemic: unlike non-systemic pesticides, they are taken up by the plant's tissues and the plant then inhibits or kills the bacteria, fungi or parasites (Encyclopedia Britannica Web Site, 1999).

Carbamate insecticides came into use later than both the organochlorines and the organophosphates and are less widely used than the others. Their use is diverse; some are used extensively for forest protection, while others are widely used against insect pests of potatoes and grains. 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. The high insecticidal activities of these chemicals allow relatively small amounts to be applied (about 100 grams/hectare) (US Geological Survey Web Site, 1999)

Although most of the groups mentioned above are insecticides, two of the best-known pesticides, 2,4-D and 2,4,5-T, are phenoxy herbicides. In fact, 2,4-D was the first successful semi-selective herbicide to be developed. After 50 years of use, products containing 2,4-D still account for one-quarter of all pesticides used in Canada (Environment Canada Web Site, 1999). Fungicides are also used in Canada, and account for about 60% of total agricultural pesticide use in the Atlantic region (Environment Canada Web Site, 1999). In addition to the main chemical groups dealt with above, there are many other pesticides on the market, such as aldehydes, amides, pyridil, isoxazol and others.