country lies destitute and in ruins. Our aim 
in the pest-control studies, as in all our work, 
is directed toward the improvement of man's 
lot in life. 
Our somewhat more humanistic approach to 
science has brought us rewards beyond meas- 
ure. But there's no law of nature that says 
we automatically and rightfully will continue 
to be so rewarded--not without great effort 
and cost. No one knows this better than the 
scientists involved in the daily business of 
wresting knowledge from an unconcerned and 
unyielding nature. 
As we understand the biology, ecology, and 
behavicr of insects ... and the proper inte- 
gration of several methods of control... I 
believe we will see, in our own lifetimes, 
the basis laid for practical, nontoxic, 
and effective methods for dealing with 
pests. 
PRESENT AND FUTURE ROLE OF PARASITES AND PREDATORS 
FOR INSECT CONTROL 
Bryan P. Beirne, Director, Research Institute, Canada Department of Agriculture, 
Belleville, Ontario 
Parasites and predators have a vast poten- 
tial for use in pest control, but this potential 
remains largely unexploited. Whether or not 
it will be adequately exploited in time to meet 
the needs of the future is debatable. 
Control of a pest insect, or, to be more 
accurate, control of the harm that the insect 
causes to man and his property, involves 
manipulating the environment to reduce or 
remove factors that are favorable to the pest 
or to add or increase factors that are un- 
favorable to it. 
Parasites and predators are among the 
factors that are unfavorable to pests. They 
are unfavorable, and thus beneficial from our 
viewpoint, because they, like chemical pesti- 
cides, kill the pests. However, unlike chemi- 
cal pesticides, they are already present in 
the environment, as virtually every insect is 
attacked by parasites and predators under 
natural conditions. 
Therefore, because they already exist, para- 
sites and predators may be manipulated for 
pest-damage control in ways that are addi- 
tional to adding them to an environment where 
they did not occur previously. In fact, they 
can be manipulated, directly or indirectly, in 
four main ways; 
First, by removing from the environment, 
or otherwise reducing the effects of, factors 
that kill parasites and predators, prevent 
them from increasing, or restrict their activ- 
ities; 
65 
Second, by adding or increasing environ- 
mental factors that are favorable to the 
multiplication or activities of parasites and 
predators; 
Third, by increasing the numbers of the 
kinds of parasites and predators that are 
already present, by liberating quantities of 
the same kinds that are obtained by mass- 
rearing or by special collections; 
And fourth, by increasing the various kinds 
of parasites and predators by liberating new 
kinds imported from elsewhere. 
All these ways are feasible. All have been 
shown to be effective pest-control methods. 
None has been used in more than a small 
fraction of the pest situations in which it 
might be effective. 
An example of the first way that is unusual 
because it is applied in many countries is the 
protection of insectivorous birds from destruc- 
tion by man. A better example of factors that 
are harmful to parasites and predators and 
that can be manipulated to decrease this 
harm is chemical pesticides. In both these 
examples man's activities are the harmful 
factors. 
It is now generally recognized that chemi- 
cal pesticides are commonly misused, and 
that they often tend to intensify existing pest 
problems and to create new ones by destroy- 
ing the parasites and predators that were-- 
before the chemicals were applied--important 
in keeping the pest from increasing unchecked. 
