FACTORS TO CONSIDER IN APPRAISING THE FEASIBILITY OF EMPLOYING 

 STERILE INSECTS FOR POPULATION CONTROL 



A number of factors must be carefully analyzed in appraising the feasibility of 

 using sterile insects for the control or elimination of established insect populations. 

 There are circumstances where the method will not be practical, and this should be 

 apparent after due consideration of all elements. On the other hand, there are circum- 

 stances where the method should be entirely practical, but for various reasons has not 

 been so regarded by research workers . 



The elements to consider will be discussed in some detail with the hope that such 

 discussion will serve as a guide for investigators who may be familiar with the biology, 

 ecology, and control of various insects, but who may not have carefully analyzed all of 

 the factors having a bearing on the use of sterile insects for population control. 



In some instances, extensive research on an insect may be necessary before even 

 a reasonable estimate of the potential of the sterile technique can be made. In other 

 instances, however, we now have enough information, if it is properly analyzed, to 

 conclude whether or not research to develop the technique is justified. 



Feasibility of Producing Sterility Without Producing Serious 

 Adverse Effects on Mating Competitiveness 



The sterile-insect-release technique requires that a method be developed for 

 producing irreversible sterility in the insect to be released. Sterility of a type that 

 destroys mating competitiveness will be of no value. The theoretical calculations in the 

 various models included in this report, are based on the assumption that the males of the 

 released organism are fully competitive. This is an assumption that may not be entirely 

 valid for most insects. 



Irradiated screw- worm flies (Cochliomyia hominivorax (Coquerel)) and tropical 

 fruit flies, as examples, show some loss in competitiveness. The use of chemosterilants 

 may result in less damage than radiation for many insects. However, if the competitive- 

 ness of the male organism released is reduced by one-half, for example, it would be 

 necessary, theoretically, to release two sterile males to fully compete with each normal 

 male. In other words, in the models previously considered, the release rate would have 

 to be two times as high to produce the theoretical effect projected, assuming that all 

 other elements are valid, as indicated. If the increase rate of an insect population were 

 tenfold per generation and the sterile males released were only one-half competitive, it 

 would be necessary to overflood the natural population with released insects at a ratio of 

 20 sterile to 1 nonsterile in order to expect a downward trend in the natural population. 

 Such problems would not, in the opinion of the writer, invalidate the practicability of the 

 sterile-insect procedure for many insects. 



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