As for many other insects , precise information is not available on natural popula- 

 tion densities of tsetse fly species, although on the basis of general information, it can 

 be assumed that for most areas the average density could be measured in terms of 

 hundreds per square mile. On the basis of costs of current eradication methods for the 

 tsetse fly, the first factor considered was the number of insects that it would be practical 

 to rear for $500. By considering the wide variations in natural population density levels 

 that may require treatment by current methods, and assuming that costs of applying 

 insecticides, brush clearing, or other methods of control would remain reasonably 

 constant, irrespective of population density, a cost figure of $1 per insect was judged to 

 be practical, in relation to current control costs, for eliminating very low populations 

 in some situations. However, it is believed that tsetse flies could be reared or collected 

 at a much lower cost. Tsetse fly investigators have shown that pupae or adults can be 

 collected from heavily infested areas at a cost substantially less than $1 per insect. It 

 seems reasonable to assume that costs in Africa for rearing the insect can eventually 

 be developed at a figure as low as 5 cents for each male, even for an insect having such 

 a low reproductive potential as the tsetse fly. Various hypothetical models were then 

 established and tested to estimate the effect of sterile male releases, taking into account 

 available information on the biology and population dynamics of tsetse flies . As will be 

 discussed in more detail later in this report, the writer concluded that tsetse flies should 

 be included among the important insects that could be eradicated by the sterility method, 

 especially in conjunction with limited use of insecticides to first reduce existing high 

 adult populations to substantially lower levels . 



By considering estimates of annual losses caused by a given insect, and costs for 

 controlling it in relation to other elements that must be considered, it should be possible 

 to make a reasonable estimate of the role of the sterile-insect technique in controlling or 

 eradicating most of our major insect pests. Consider the codling moth, for example. It 

 costs growers about $50 per acre each year to control the codling moth. For an insect 

 that has such restricted hosts and obviously exists at a low-density level in commercial 

 apple orchards intensively treated with insecticides, it would seem likely that the 

 production of adequate numbers of codling moths for use in control would not be a major 

 problem from a cost standpoint. If we assumed a cost figure of $5 per 1, 000 for rearing 

 and releasing codling moths on a mass-production basis, $50 would purchase 10, 000 

 sterile insects and still be competitive in cost with insecticides. If the minimum cost of 

 $1 per 1,000 moths could be achieved for rearing codling moths, it would be feasible to 

 rear 50, 000 sterile moths for use on each acre, each year. Although good data on 

 natural population densities are not available, it seems obvious that the spring population 

 of the insect in well-cared-for orchards will not exceed more than a few hundred moths 

 per acre, and that it should be possible, without excessive cost, to further reduce the 

 natural population, including populations from imtreated domestic and wild host trees. 

 Such appraisal suggested that the release of a few thousand sterile insects per acre 

 should provide a high ratio of sterile to fertile moths. On the basis of this reasoning, 

 the writer regards the codling moth a favorable candidate for control by the sterile- 

 insect-release method. The eradication of codling moths from certain areas may be 

 difficult, but an important factor to consider is that once an established population is 

 under complete domination by sterile insects, but subject to reinfestation from 



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