This section is from the book "Commercial Gardening Vol1", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
While the life-history and habits of the various insects that prey upon plants may possess a charm for the entomologist, the man who has to grow plants, flowers, fruits, and vegetables for a living is by no means enamoured of them. No matter how interesting and beautiful an insect may be in the various stages of its development, the cultivator looks upon it as an unmitigated nuisance, that must be suppressed at all costs. He regards nearly all insects as highway robbers, who not only take money out of his pocket for insecticides, but who add insult to injury by lowering or spoiling the market value of his produce, and preventing the proper development of his plants.
Now, apart from insecticides there is another and more natural way of combating these marauders. The cultivator should make himself acquainted with the habits of the various pests, so that he may discover their weakest and most vulnerable points. Having found these, then is the time to attack them vigorously, when they are neither able to resist nor escape; and although his efforts may not be crowned with complete success, he will have the satisfaction of knowing that he has reduced his tormentors to practically harmless proportions.