Integrated control programs can overcome this 
problem. 
Integrated controls are control measures 
applied in such a way that their effects do not 
counteract either one another or the effects 
of naturally existing factors that regulate pest 
numbers. In its simplest form, an integrated 
control is the use of chemical pesticides in 
such a manner that they do little or no harm 
to the parasites and predators that attack the 
pest. More usually, integrated controls involve 
manipulating, in addition, parasites, predators, 
and other controls. 
The rate at which an optimum integrated 
control program can be developed for any 
pest situation depends on the rate at which 
knowledge is obtained on the identities, life 
histories, habits, and ecology of the parasites, 
predators, and other natural enemies of the 
pest. When we have such information, we can 
both manipulate the natural enemies of the 
pest to increase their effectiveness and at 
the same time plan modifications of chemical 
treatments on a basis of facts, so that the 
chemicals will have little or no effects on the 
natural enemies, 
Unfortunately existing knowledge is often 
quite inadequate. For example, in Canada 
there are about 2,000 kinds of insects that 
are harmful to agriculture. But some infor- 
mation on the identities of their parasites 
and predators is available for only under 
one-third of them, and in only a few instances 
is the information sufficiently adequate to 
form a basis on which optimum integrated 
control programs might be developed. When 
you consider this situation in the context of 
the fact that insect pests have been studied 
in Canada as intensively as in any country 
and more intensely than in most, you will 
appreciate how much remains to be done 
everywhere. Good integrated control pro- 
grams have been developed, for example, that 
for the spotted alfalfa aphid in the Western 
United States, but they are still exceptions 
rather than the rule. 
However, it is possible to develop rather 
effective integrated control programs on a 
basis of probabilities. These probabilities, 
which are in practice virtual certainties, are 
that parasites and predators that attack the 
pest are present, they are not always where 
the pest is, and when they are where the 
66 
pest is they are liable to be killed by chemi- 
cal pesticides. Therefore, chemical applica- 
tions that are reduced to the minimum in 
terms of time and quantity will have the 
minimum of harmful effects on the parasites 
and predators, which will therefore survive 
to assist in controlling the pest numbers. 
A program of this kind was developed by 
the Canada Department of Agriculture for fruit 
tree pests in Nova Scotia, and is widely used 
by growers in that Province. Similar pro- 
grams could be developed for other pest 
Situations and in other areas, In most in- 
stances, they have yet to be developed, but 
they doubtless will be. 
The second way that I mentioned of manipu- 
lating parasites and predators to increase 
their numbers is to increase environmental 
factors that are favorable to them. This is 
a little-used approach but one that has much 
potential. But again, a knowledge of the 
ecology and behavior of the parasites and 
predators involved is an essential prerequi- 
site. 
This method is based on the principle that 
most parasites and predators have essentials 
for survival and increase that are not pro- 
vided by the pest itself or its immediate 
environment. The parasites must go elsewhere 
to find the alternate hosts on which they 
complete their annual life cycles, or to find 
the food that the adult females must have 
before they lay their eggs. The predators 
must go elsewhere to find alternative prey 
on which to build up their numbers or to 
survive periods when the pests are not avail- 
able to them. And both parasites and predators 
may require special hibernation or nesting 
sites, 
In some pest Situations in Western Europe, 
nesting sites are deliberately provided for 
birds and ants that prey upon the pests. In 
the Soviet Union, various pests are stated to 
be kept under satisfactory control by growing 
with the crop the wild flowers on which the 
adult parasites must feed before they can lay 
their eggs on the pest. 
In general, the value of this method seems 
to be better recognized in Europe than in 
North America, though there is a classic 
example, apparently still unpublished, of the 
control of a grape pest in California by con- 
serving the alternate host that was essential 

