By R. L. Doutt, Ray F. Smith (auth.), C. B. Huffaker (eds.)
The explosive raise within the world's human inhabitants, with conse quent have to feed an ever-increasing variety of hungry mouths, and the mostly resultant disturbances and toxins of our environment within which guy needs to stay and bring the issues he wishes, are forcing him to look for technique of fixing the 1st challenge with no intensifying the latter. meals construction calls for enough insurance opposed to the ravages of bugs. within the final 3 a long time short-sighted, unilateral and nearly particular employment of synthesized chemical compounds for insect pest keep an eye on has posed a tremendous and as but unfathomed contribution to the degradation of our surroundings, whereas our insect pest difficulties appear more than ever. appropriately seen, pest keep an eye on is essentially a query of utilized ecology, but its perform has lengthy been performed with little regard to genuine necessity for keep watch over, and occasionally, with little regard to numerous hazardous side-effects or long term virtue with admire, even, to the explicit crop itself. This booklet offers essentially with those questions. the improvement of pesticide resistance in lots of of the objective species, opposed to which the insecticides are directed, has occasioned an ever-increasing load of functions and complexes of alternative varieties of hugely poisonous fabrics. This has been made much more "necessary" because the destruction of ordinary enemies has resulted, as an aspect influence, within the upward push to pest prestige of many species that have been previously harmless. the applying of broad-spec trum insecticides hence has many severe and self-defeating features.
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Populations in widely varying environments are expected to vary widely unless they are under control by factors other than competition for food or 18 C. B. HUFFAKER, P. S. MESSENGER, AND PAUL DEBACH suitable habitats or shelters-factors which vary greatly with the varying meteorological conditions. Thus, the beet leafhopper, Circulifer tene/lus (Baker) in western United States and in arid areas of Eurasia and Africa, or the plague locust, Schistocerca gregaria (Forskal) in various regions of the world, may vary many thousand-fold between their lowest and greatest abundance.
Moreover, recent work alluded to above points to a number of features intrinsic to the interaction itself that serve as damping features. In these studies two rather distinct approaches were used. In the approach of Hassell and Huffaker (1969b) and Hassell and Varley (1969), the components of the attack process (as used in a Holling approach) were not utilized; rather, the modeling was based on the Nicholsonian approach. In the former paper, it was found that direct and/or indirect interference between parasites (Venturia canescens (Gravenhorst» served as a damping feature; this resulted in a variation in the "area of discovery" (assumed constant under the Nicholson conception) and the quantitative description of this variation furnished a Significant feature of the predictive equation for both host and parasite populations.
These relationships and others pose interesting questions regarding the merits of predators versus parasites as biological control agents. Doutt and DeBach (1964) discussed this question and the related questions of degree of host specificity and powers of prey consumption. Huffaker et al. (1969) considered the latter points relative to control of tetranychid mites by predators. , in general, parasites are more host-specific, more closely adapted and synchronized in interrelationships, their lower food requirements permit them to maintain a balance with their prey species at a lower prey density, and the young (the less active stages) do not have to search for their food.