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Most of the heat and radioactivity from spent nuclear fuel dissipates within 50 years. For more information, see: For a lesson about this topic, see: |
In the late 1960s Canada’s forests were under attack by a species of insect known as choristoneura fumiferana. This insect, also known as the gypsy moth, lays its eggs in the needles of spruce and fir trees. When the eggs hatch, the larvae, known as the spruce budworm, consume the needles on the tips of branches. After three or four seasons, the tree often dies. One of the areas hardest hit by the spruce budworm was Atlantic Canada. The infestation covered all areas of most provinces causing a great deal of damage to forests and threatening the softwood lumber industry, a major employer in Atlantic Canada.
In response to the outbreak, many provinces began an aerial spray program. In New Brunswick the chemical pesticide fenitrothion was used. Anyone in New Brunswick over the age of 35 will remember the World War II vintage Avenger bombers as they flew across the sky spraying their cargo of pesticide over the tree tops. By the late 1970s, people had begun to raise concerns about the possible negative impacts of chemical pesticides on wildlife and human health. When chemical insecticides are used in such a manner, all creatures that happen to be in the spray path may come into contact with the pesticide and other animals such as birds may eat insects and worms which have been sprayed and ingest the chemical. The pesticide will also eventually find its way into the waters and soils of the spray area. The use of fenitrothion was banned in New Brunswick in 1998.
In the 1980s the spray program switched to natural biological pesticides, one of which was a baculovirus specifically designed to target the spruce budworm and not harm other wildlife. This biological pesticide was also sprayed from airplanes and the budworms would die about 14 days after eating the tree needles covered with baculovirus. Again, public concerns over the impact on wildlife and human health were raised. Other biological agents which continue to be developed and tested in limited quantities, include tebufenozide, which is a biological growth inhibitor, as well as a number of biological pheromones which inhibit mating among adult gypsy moths.
By the mid 1990s the outbreak had subsided and the spray programs in Atlantic Canada effectively ended. However, outbreaks of the spruce budworm occur about every 35 years, meaning Canada is almost due for another outbreak. With many of the chemical pesticides used in the past now banned and questions about the true environmental impact of biological agents not yet fully understood, what other possible alternatives exist to help control or eradicate insect pests like the spruce budworm? One possible alternative is ionizing radiation.
Ionizing radiation was first used on the island of Curacao in 1954 to eradicate the screwworm which had had devastating effects on livestock and wildlife. In this process, male insects are placed in a shielded container containing a gamma ray emitting a radioactive isotope of either cobalt-60 or cesium-137. While in the chamber, low doses of gamma radiation sexually sterilize the insects which are then released back into the wild. When the insects mate, no offspring are produced, effectively controlling the population. This technology has proven to be effective, safe and environmentally friendly because it releases no chemical, biological or nuclear agents into the environment. Currently, this technology is being used in the United States, Mexico, and parts of Africa.
Resources:
Natural Resources Canada cfs.nrcan.gc.ca/index/sprucebudworm
Government of Manitoba: www.gov.mb.ca/conservation/forestry/brochures/spruce_budworm.pdf
Canadian Forest Service: cfs.nrcan.gc.ca/factsheets/baculoviruses
Hans Tammemagi and David Jackson, Unlocking the Atom: The Canadian Book on Nuclear Technology, McMaster University Press, 2002 .