A SYNOPSIS O F THE PESTICIDE PROBLEM
85
be seen that in no case do available data approach what is required.
For most other species both in Britain and elsewhere even less information is available.
It might be thought from what has been said in this section that the
study of pesticide effects contains so many unknown factors that evaluation is pointless. On the other hand the use of pesticides raises so many
practical problems that we have to attempt to understand their effects.
In the present state of ignorance we rarely expect to do more than
bring a little order into chaos and to provide tentative answers.
111. PESTICIDES AS AN ECOLOGICAL FACTOR: ITS DEVELOPMENT
AND PRESENT MAGNITUDE
While difficulties in interpreting the effects of pesticides might be
expected, the measurement of the pesticide factor itself might be
thought to be a simple matter. In practice it is not. For all studies on
the effects of pesticide use it is essential to know the quantity of active
ingredient and how and when it was applied. I n dealing with localized
effects the minimal information (unit weight per unit area, type of
spraying machinery and date) can be obtained from the farmer or
contractor. However, studies on pesticide application show that even
under ideal conditions spraying treatments usually result in an uneven
distribution of the pesticide. The practical difficulties of determining
the exact distribution of spray on the treated area are so great that
this is rarely done. For an exception see Giles and Peterle (1963), who
studied the distribution of malathion after spraying by labelling the
material with 3%. Even when the average rate of application may
cause little damage, localized concentrations of pesticide are likely to
occur and these may be hazardous.
In going from localized areas such as an experimental orchard or
field to large parts of the earth surface, and from local populations to
ranges of species, the same general categories of information on use are
still required. Unfortunately they are rarely available because annual
statistics for different types of pesticide use are not kept by any country.
It is impossible to give accurate figures for present day use or to describe
accurately the development of pesticide use during the last quarter of
a century. However, from the evidence available, it is possible to give
a general picture of the trend and the order of magnitude of pesticide
use. The earlier history of pesticide use has been recorded by several
authors, e.g. Metcalf (1955) and Martin (1964). Nicotine was used as an
insecticide in the mid-18th century. By the end of the 19th century a
number of substances in common use today we;e being used, for
example Bordeaux mixture, lime sulphur and dinitrocresol. BHC and
DDT were both synthesized in the 19th century but their insecticidal
D
85
be seen that in no case do available data approach what is required.
For most other species both in Britain and elsewhere even less information is available.
It might be thought from what has been said in this section that the
study of pesticide effects contains so many unknown factors that evaluation is pointless. On the other hand the use of pesticides raises so many
practical problems that we have to attempt to understand their effects.
In the present state of ignorance we rarely expect to do more than
bring a little order into chaos and to provide tentative answers.
111. PESTICIDES AS AN ECOLOGICAL FACTOR: ITS DEVELOPMENT
AND PRESENT MAGNITUDE
While difficulties in interpreting the effects of pesticides might be
expected, the measurement of the pesticide factor itself might be
thought to be a simple matter. In practice it is not. For all studies on
the effects of pesticide use it is essential to know the quantity of active
ingredient and how and when it was applied. I n dealing with localized
effects the minimal information (unit weight per unit area, type of
spraying machinery and date) can be obtained from the farmer or
contractor. However, studies on pesticide application show that even
under ideal conditions spraying treatments usually result in an uneven
distribution of the pesticide. The practical difficulties of determining
the exact distribution of spray on the treated area are so great that
this is rarely done. For an exception see Giles and Peterle (1963), who
studied the distribution of malathion after spraying by labelling the
material with 3%. Even when the average rate of application may
cause little damage, localized concentrations of pesticide are likely to
occur and these may be hazardous.
In going from localized areas such as an experimental orchard or
field to large parts of the earth surface, and from local populations to
ranges of species, the same general categories of information on use are
still required. Unfortunately they are rarely available because annual
statistics for different types of pesticide use are not kept by any country.
It is impossible to give accurate figures for present day use or to describe
accurately the development of pesticide use during the last quarter of
a century. However, from the evidence available, it is possible to give
a general picture of the trend and the order of magnitude of pesticide
use. The earlier history of pesticide use has been recorded by several
authors, e.g. Metcalf (1955) and Martin (1964). Nicotine was used as an
insecticide in the mid-18th century. By the end of the 19th century a
number of substances in common use today we;e being used, for
example Bordeaux mixture, lime sulphur and dinitrocresol. BHC and
DDT were both synthesized in the 19th century but their insecticidal
D