so that small song birds cannot eat them. The undesirable drugged birds can then be
destroyed, allowing the desirable ones to recover in a safe place with no ill effect.
The major difficulty with chemical approaches for vertebrate pest control is that
enormous testing is necessary for the use of the chemical. Testing with respect to
effect on nontarget organisms, biodegradation, lethal dose, and so on is expensive,
and many of the vertebrate pest problems, although very serious, are also very
limited in scope.
8 Resistance to Chemical Pesticides
Over a period of time of a particular pesticide’s use, it is expected that many
pesticides will become resistant to the originally targeted pest. Indeed, the problem
of insect resistance has stimulated the development of new insecticides. Nearly all of
the established insecticides have induced resistance in some insects. The mechanism
of insect resistance may be morphological, behavioral, or biochemical. The selective
advantage of some adaptation in structure, behavior, or metabolism in members of a
population produces resistance in certain insects. Very commonly the successful
mutant possesses an enzyme mechanism for detoxifying an organochemical poison,
thereby necessitating the use of a different class of compounds. This problem of
resistance does not exist as much with the inorganic pesticides, since the possibility
for chemical modification by the organism is much less among the inorganic
poisons.
A general rule worth observing is that two classes of organic pesticides may not
be used simultaneously. Such use encourages the disastrous appearance of a double
mutant resistant to both agents. The agents should be used sequentially instead, if
needed. Thus, mutants resistant to the first agent will be killed by the second. Further
mutation is unlikely to occur without a loss of the initial resistance.
The use of an insecticide like dichlorvos is not ecologically wise according to this
rule. Dichlorvos contains the insecticidal moiety of both the organophosphorus and
the organochlorine insecticides making it doubly lethal, but also conducive to the
selection of a double mutant resistant to both classes of insecticides.
Unfortunately, all the pests that we wish to control are more adaptable than
humans to a changing environmental chemistry, and pesticide resistance in insects
is common.
Just as the inappropriate use of pharmaceuticals leads to drug-resistant tuberculosis, pest resistance to pesticides is also being accelerated by human error and
misuse. For example, when pesticide phosphine gas exposure times are shortened
during the fumigation of agriculture or wood commodity to save time, the remaining
insects that are not killed, are more resistant to the next application. Pesticide
resistance monitoring is a key facet of effective pesticide use and is typically carried
out by municipal agricultural extension agencies, research universities, and professional pesticide applicators.
10 Environmental Control of Pests and Vectors
405
destroyed, allowing the desirable ones to recover in a safe place with no ill effect.
The major difficulty with chemical approaches for vertebrate pest control is that
enormous testing is necessary for the use of the chemical. Testing with respect to
effect on nontarget organisms, biodegradation, lethal dose, and so on is expensive,
and many of the vertebrate pest problems, although very serious, are also very
limited in scope.
8 Resistance to Chemical Pesticides
Over a period of time of a particular pesticide’s use, it is expected that many
pesticides will become resistant to the originally targeted pest. Indeed, the problem
of insect resistance has stimulated the development of new insecticides. Nearly all of
the established insecticides have induced resistance in some insects. The mechanism
of insect resistance may be morphological, behavioral, or biochemical. The selective
advantage of some adaptation in structure, behavior, or metabolism in members of a
population produces resistance in certain insects. Very commonly the successful
mutant possesses an enzyme mechanism for detoxifying an organochemical poison,
thereby necessitating the use of a different class of compounds. This problem of
resistance does not exist as much with the inorganic pesticides, since the possibility
for chemical modification by the organism is much less among the inorganic
poisons.
A general rule worth observing is that two classes of organic pesticides may not
be used simultaneously. Such use encourages the disastrous appearance of a double
mutant resistant to both agents. The agents should be used sequentially instead, if
needed. Thus, mutants resistant to the first agent will be killed by the second. Further
mutation is unlikely to occur without a loss of the initial resistance.
The use of an insecticide like dichlorvos is not ecologically wise according to this
rule. Dichlorvos contains the insecticidal moiety of both the organophosphorus and
the organochlorine insecticides making it doubly lethal, but also conducive to the
selection of a double mutant resistant to both classes of insecticides.
Unfortunately, all the pests that we wish to control are more adaptable than
humans to a changing environmental chemistry, and pesticide resistance in insects
is common.
Just as the inappropriate use of pharmaceuticals leads to drug-resistant tuberculosis, pest resistance to pesticides is also being accelerated by human error and
misuse. For example, when pesticide phosphine gas exposure times are shortened
during the fumigation of agriculture or wood commodity to save time, the remaining
insects that are not killed, are more resistant to the next application. Pesticide
resistance monitoring is a key facet of effective pesticide use and is typically carried
out by municipal agricultural extension agencies, research universities, and professional pesticide applicators.
10 Environmental Control of Pests and Vectors
405