Biodegradable Insecticides in Forestry
161
The major method for suppressing insect outbreaks, especially of defoliators, is by chemical means (Ciesla, 1976, 1977; Fettes and Buckner, 1976;
Graham, 1975; Johnson and Lawrence, 1977; Krebs, 1976; Lyon, 1974; NAS,
1975b; Mrak, 1969; Pimentel et al., 1978; and Sanders, 1976). Chemicals are
used because no viable immediate alternative exists to suppress an outbreak
(Honing, 1976; Pimentel et al., 1978). The availability of insect-resistant trees
has been slow to develop (Irving, 1970). Microbials have been used with some
success (Morris, 1977). Biological control in forestry (Pschorn-Walcher, 1977)
is a young, unproven science. And pheromone strategies for the manipulation
of forest insects to control outbreaks or suppress them (Wood, 1977) remain to
be realized.
Some scientists are opposed to the use of chemicals on the grounds that
insects soon develop resistance to chemicals and that this approach will prove
to be ineffective (Luck et al., 1977). Resistance has not been a major problem,
however, in forest pest management. Furthermore it remains to be proven that
chemicals will provide a no-risk input into the environment. The cost of R&D
in the continuing search for new chemicals (Rumker et al., 1970), biologicals
(pschorn-Walcher, 1977), and pheromones (Wood, 1977) continues to escalate.
Likewise, the controversy continues over which pest management strategy is
best. Perhaps in the near future pest management by biological control can be
upgraded to a profit-making enterprise and become competitive with insecticides.
From 1945 to 1974, a total of 35 forest insect pests were treated with
insecticides over an area covering approximately 52 million hectares in the United
States and considerably more in Canada. The land infested by the western spruce
budworm and gypsy moth accounted for 82.4% of this area (NAS, 1975b). To
accomplish this spray program, which was primarily for budworm, extending
over 29 years, 20.4 million pounds of insecticide was used, and in Canada this
figure must be considerably higher. The most widely used insecticide was DDT.
Since the banning of DDT in 1972, the insecticide mass applied to forests has
been approximately 15% of the pre-1968 totals (NAS, 1975b). More recently,
the insecticides used in control programs and large experimental tests were
carbaryl, mexacarbate, malathion, trichlorfon, fenitrothion, tetrachlorvinphos,
aminocarb, phosphamidon, dimethoate, and propoxur.
7.3. USE OF DDT: 1945-1974
Chemical control of budworm in Canada and the United States began in the
late 1940s, after DDT had been developed and military aircraft could be refitted
to conduct large-scale operations (Fettes and Buckner, 1976). By 1954 several
million acres were being sprayed (Ciesla, 1976) without any regard for environmental impact by current standards. In 1962, a total of 920,000 pounds of
161
The major method for suppressing insect outbreaks, especially of defoliators, is by chemical means (Ciesla, 1976, 1977; Fettes and Buckner, 1976;
Graham, 1975; Johnson and Lawrence, 1977; Krebs, 1976; Lyon, 1974; NAS,
1975b; Mrak, 1969; Pimentel et al., 1978; and Sanders, 1976). Chemicals are
used because no viable immediate alternative exists to suppress an outbreak
(Honing, 1976; Pimentel et al., 1978). The availability of insect-resistant trees
has been slow to develop (Irving, 1970). Microbials have been used with some
success (Morris, 1977). Biological control in forestry (Pschorn-Walcher, 1977)
is a young, unproven science. And pheromone strategies for the manipulation
of forest insects to control outbreaks or suppress them (Wood, 1977) remain to
be realized.
Some scientists are opposed to the use of chemicals on the grounds that
insects soon develop resistance to chemicals and that this approach will prove
to be ineffective (Luck et al., 1977). Resistance has not been a major problem,
however, in forest pest management. Furthermore it remains to be proven that
chemicals will provide a no-risk input into the environment. The cost of R&D
in the continuing search for new chemicals (Rumker et al., 1970), biologicals
(pschorn-Walcher, 1977), and pheromones (Wood, 1977) continues to escalate.
Likewise, the controversy continues over which pest management strategy is
best. Perhaps in the near future pest management by biological control can be
upgraded to a profit-making enterprise and become competitive with insecticides.
From 1945 to 1974, a total of 35 forest insect pests were treated with
insecticides over an area covering approximately 52 million hectares in the United
States and considerably more in Canada. The land infested by the western spruce
budworm and gypsy moth accounted for 82.4% of this area (NAS, 1975b). To
accomplish this spray program, which was primarily for budworm, extending
over 29 years, 20.4 million pounds of insecticide was used, and in Canada this
figure must be considerably higher. The most widely used insecticide was DDT.
Since the banning of DDT in 1972, the insecticide mass applied to forests has
been approximately 15% of the pre-1968 totals (NAS, 1975b). More recently,
the insecticides used in control programs and large experimental tests were
carbaryl, mexacarbate, malathion, trichlorfon, fenitrothion, tetrachlorvinphos,
aminocarb, phosphamidon, dimethoate, and propoxur.
7.3. USE OF DDT: 1945-1974
Chemical control of budworm in Canada and the United States began in the
late 1940s, after DDT had been developed and military aircraft could be refitted
to conduct large-scale operations (Fettes and Buckner, 1976). By 1954 several
million acres were being sprayed (Ciesla, 1976) without any regard for environmental impact by current standards. In 1962, a total of 920,000 pounds of