A SYNOPSIS OF THE PESTICIDE PROBLEM
89
carbamates, etc.). The chemistry of pesticides and their properties are
described in a number of handbooks; particularly valuable are the works
of Brown (1951), Metcalf (1955) and Martin (1964). The characteristics
of some pesticides of probable ecological importance in Britain are given
in Table 111. All except dalapon, which is included because it is much
used in fresh water, have one or more of the following characteristics:
(i) They are used on more than 100 000 acres each year in England
and Wales (see Strickland, 1966).
(ii) They are highly toxic (acute oral toxicity LD50 to rat is less than
(iii) They persist in soils for more than one year.
20 mg/kg).
Pesticides vary considerably in their nature but they share the following
characteristics :
(i) They are designed and used by man to kill some form of living
organism.
(ii) They are used against populations of organisms.
(iii) The amount which has to be used is far in excess of the amount
required to kill the pest.
(iv) They are used against a very small proportion of the world’s
species (less than 0.5%).
(v) They are generally used when a population of at least one species
(the pest) is present in abnormally high numbers. t
(vi) They are non-specific in their effects.
(vii) Their action on populations is usually density independent. t
Some exceptions should be mentioned. Chemosterilants do not kill
the organisms but prevent reproduction. Poisons are sometimes used
against individual vertebrate animals, for example against a rogue
predator. At least one specific pesticide is on the market; this is Norbormide, a rodenticide which appears to be specific to the genus Rattus.
Some of these common characteristics and their effects are elaborated
below.
2. Non-speci$city
Pesticides have radical effects on ecosystems because they are nonspecific. The effect of a specific pesticide would be homologous to specific
disease or selective predation by one species on another. Even so it
could have important effects because the elimination or great reduction
of any wild species is bound to affect others in the same ecosystem. If
the species is an important or key species, determining major features
of the ecosystem, its disappearance may have widespread effects. For
example, the great reduction of the European rabbit in Great Britain
which followed the introduction of the myxoma virus led to widespread
t Note that the applications but not the effects are density-dependent.
89
carbamates, etc.). The chemistry of pesticides and their properties are
described in a number of handbooks; particularly valuable are the works
of Brown (1951), Metcalf (1955) and Martin (1964). The characteristics
of some pesticides of probable ecological importance in Britain are given
in Table 111. All except dalapon, which is included because it is much
used in fresh water, have one or more of the following characteristics:
(i) They are used on more than 100 000 acres each year in England
and Wales (see Strickland, 1966).
(ii) They are highly toxic (acute oral toxicity LD50 to rat is less than
(iii) They persist in soils for more than one year.
20 mg/kg).
Pesticides vary considerably in their nature but they share the following
characteristics :
(i) They are designed and used by man to kill some form of living
organism.
(ii) They are used against populations of organisms.
(iii) The amount which has to be used is far in excess of the amount
required to kill the pest.
(iv) They are used against a very small proportion of the world’s
species (less than 0.5%).
(v) They are generally used when a population of at least one species
(the pest) is present in abnormally high numbers. t
(vi) They are non-specific in their effects.
(vii) Their action on populations is usually density independent. t
Some exceptions should be mentioned. Chemosterilants do not kill
the organisms but prevent reproduction. Poisons are sometimes used
against individual vertebrate animals, for example against a rogue
predator. At least one specific pesticide is on the market; this is Norbormide, a rodenticide which appears to be specific to the genus Rattus.
Some of these common characteristics and their effects are elaborated
below.
2. Non-speci$city
Pesticides have radical effects on ecosystems because they are nonspecific. The effect of a specific pesticide would be homologous to specific
disease or selective predation by one species on another. Even so it
could have important effects because the elimination or great reduction
of any wild species is bound to affect others in the same ecosystem. If
the species is an important or key species, determining major features
of the ecosystem, its disappearance may have widespread effects. For
example, the great reduction of the European rabbit in Great Britain
which followed the introduction of the myxoma virus led to widespread
t Note that the applications but not the effects are density-dependent.