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Title: Studies on the natural control of noxious weeds and injurious insects, with special reference to insect parasites
Author: Cameron, Ewen
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1940
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The papers contained in this Thesis aim at illustrating the three most important aspects of biological control. I. The control of noxious weeds by phytophagous insects. II. The control of injurious insects by entomophagous insects. III. The stud of insect parasites especially in their developmental stages. (A knowledge of these immature stages is absolutely essential to the proper handling of the insects both in the country of collection and of liberations). The germ 'Natural Control' is generally understood to mean the check exerted on the multiplication of organisms by natural as opposed to artificial environmental factors. It includes all the factors (apart from artificial) both animate and inanimate, which tend to reduce the numbers of the pest in question. 'Biological Control', on the other hand, takes into account only the living or biotic factors, and these, because of the comparative ease with which they can be handled, are usually reduced to the indigenous insect enemies - parasites and predators ® and, in the case of weeds, phytophagous insects. Although these insect enemies are of prime importance, the other factors operating on the pest in question, must on no account be neglected. In the following papers, therefore, the various problems have been treated, so far as possible, from the wider natural control point of view. The general principles underlying the biological control of insect pests have been thoroughly dealt with by various writers, including Dr. W.R. Thompson, Dr. A.D. lams, H.S. Smith, etc., etc., while a textbook on the subject was recently published by H.L. Sweetman, so that it would be mere vain repetition to go over this ground again. In the Ragwort paper, however, the principles of weed control by phytophagous insects have been laid down, and the general methods of dealing with an insect pest are embodied in the publication on the Pea Moth. As already pointed out, the recognition of the immature stages of the various parasites is all important in work of this kind, and a great deal of time has been devoted to the study of these. Examples of this work may be found in the following papers, but especially in No. 3, where some curious formations are described. With regard to the two supporting papers, it may be stated that the present writer was responsible for all the work done on Microplectron fuscipennis (No.4), with the exception of the account of its distribution,and part of section eleven. His share in paper No. 5 consisted of the data relating to the following parasites : Microcryptus basizonius, Hemiteles areator, Delomerista sp., Pimple alternans, Lamachus sp., and part of the descriptions of most of the others. He was also mainly responsible for the formation of the keys to the various parasites. The present position of the various beneficial insects described in the following papers may be briefly summarized as follows. Tyria jacobaeae does not appear to be exerting any appreciable effect on Ragwort in New Zealand, chiefly because of the attacks of native parasites. The Anthoinyiid seed -fly, Pegohylezgyia seneciella is still being experimented with, and according to the New Zealand authorities, is showing hopeful signs of usefulness, Before control of this weed can be obtained, however, the various measures advocated in the following paper, such as the elimination, so far as possible, of factors predisposing to open soil conditions, etc., must be carried out. News has just been received that the Pea Moth parasites sent from this country to Canada, have become established and great hopes are entertained for the successful outcome of this experiment in biological control. Opius ilicis, Microplectron fuscipennis, Microcryptus basizonius, and many other parasites have become established in Canada as a result of our introductions, and many of them are already exerting some measure of control. It may be interesting to note that the Chalcid, Microplectron fuscipennis, is now being bred on factory proportions in special insectaries at Belleville, Ontario, and millions of these useful parasites are being produced there for distribution to various parts of Canada.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (D.Sc.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available