THE PRACTICE AND THEORY OF BIOLOGICAL CONTROL OF INSECTS IN CANADA

This paper constitutes a "stocktaking" of biological control in Canada. The success or failure of each of 31 Canadian biological control projects is assessed. Past experiences in Canada are analyzed, and recommendations for future work are made. The meaning of the term "control" is defined in an economic context. Lloyd's (1960) suggestion regarding the influence of host plant longevity on the success of biological control is rejected, and a new concept based on the type of injury inflicted by the pest is substituted. There is a discussion on the philosophy of biological control and some of the popular misconceptions regarding it. Some dangers of biological control are suggested. Smith's (1929) analysis of the population effects of multiparasitism is challenged. The simultaneous introduction of many exotic species of parasites and predators is not favored and a strong plea for more discrimination and caution in the selection of species for introduction is voiced. The need for research in this field is emphasized, and fields of research are suggested. The philosophy of a biological control research program is outlined.