even though the population gradually increases 

 throughout the season. In these cases the re- 

 lease ratio is high, the frequency of the condi- 

 tional lethal allele in the release strain is very 

 high, and the native population increases ten- 

 fold per generation in three of these cases and 

 twentyfold in the other. On the other hand, 

 complete suppression is assured when the re- 

 lease strain is far from homozygous for the 

 conditional lethal allele (q 2 = 0.05) in cases 22, 

 27, and 37. 



Cases 1, 2, and 3 in table 2 illustrate the 

 desirability of using a release strain that 

 approaches homozygozity for the conditional 

 lethal allele. In these cases if the population 

 has four or five generations per year, complete 

 -suppression would not be achieved if q 2 is 0.05. 

 Complete suppression might be achieved when 

 q 2 is 0.01, and complete suppression would al- 

 most certainly be achieved if q 2 is 0.001. 



If we assume that a population of fewer than 

 100 individuals in the fall generation will be 

 eradicated because of mortality during the win- 

 ter and that a population of more than 100 will 

 survive, then the presence of the dominant con- 

 ditional lethal allele will assure complete sup- 

 pression in a population with four or five 

 generations per year in cases 3, 18, 22, 23, 24, 

 27, 29, 30, 31, 37, 38, and 39. Complete suppres- 

 sion would have been achieved without the con- 

 ditional lethal allele in cases 7, 8, 9, 13, 14, 15, 

 and 32. Cases in which the use of a dominant 

 conditional lethal allele would be useful in sup- 

 pressing populations that have only two or 

 three generations per year may be ascertained 

 by inspecting table 2. If the population has 

 only two generations per year, complete sup- 

 pression cannot be achieved in a single season 

 without very high release ratios, a high level of 

 sterility, and a high frequency of the condition- 

 al lethal allele. 



SUMMARY 



To evaluate the use of sterile male insects 

 for suppression of a pest population, one must 

 know the magnitude of the release ratio and the 

 level of male sterility required to eradicate the 

 target population. The magnitude of these 

 variables depends on the rate of increase of the 

 pest population. The interrelationships between 

 the release ratio, the level of sterility, and the 

 rate of increase are quantitatively illustrated. 



Generally if low release ratios must be used 

 to suppress a pest population, a higher level 

 of sterility is required than when high release 



ratios may be used. On the other hand, if high 

 release ratios may be used, the level of sterility 

 required for population suppression may be 

 lower than if low release ratios must be used. 

 When the rate of increase of the pest popula- 

 tion is high, it is frequently more advantageous 

 to impair competitiveness in order to achieve a 

 high level of sterility than to use a slightly 

 lower level of sterility with full competitive- 

 ness. A considerable bonus effect would be 

 realized by constituting a release strain with a 

 dominant conditional lethal trait. 



Washington, D.C. 



Issued January 1971 



For sale by the Superintendent of Documents, U.S. Government Printing Office 

 Washington, D.C. 20402- Price 15 cents 



* U. S. GOVERNMENT PRINTING OFFICE : 1973 O - 492-709 



