SUPPRESSION OF PEST POPULATION 

 WITH STERILE MALE INSECTS 



By Waldemar Klassen and James P. Creech 1 



In order to plan large-scale field experiments 

 to evaluate the use of sterile male insects for 

 suppression of a pest population, one must 

 know the level of male sterility and the magni- 

 tude of the release ratio required to eradicate 

 the target population. The magnitude of these 

 variables depends on the rate of increase of the 

 pest population. The rate of increase is deter- 

 mined by the number of eggs laid by the female 

 and by the action of weather, predators, para- 



site diseases, and other mortality factors. Ob- 

 viously the rate of increase is subject to wide 

 fluctuation between localities, between consecu- 

 tive generations, and between years. We must 

 know what is required in terms of the release 

 ratios and the levels of sterility to deal with 

 populations undergoing average or explosive 

 rates of increase. (The rate of increase is de- 

 fined as one-half the number of progeny pro- 

 duced by a female.) 



PROCEDURES 



To fulfill this need, we have computed a 

 number of cases in which we assume that we 

 are dealing with a target area of 1,000 acres 

 on which the pest population has been reduced 

 to 1,000 males and 1,000 females. This popula- 

 tion may have from one to five generations per 

 year. The release ratios at the outset of the 

 program are 100:1, 50:1, 25:1, and 12.5:1 

 (sterile males :native males; females if released 

 are fully sterile). The level of male sterility is 

 90, 95, 98, 99, and 100 percent, and the rate of 

 increase from generation to generation is five- 

 fold, tenfold, twentyfold, and fortyfold. This 

 type of model was employed by Knipling. 2 



1 Waldemar Klassen, entomologist, Entomology Re- 

 search Division, Agricultural Research Service, and 

 James F. Creech, graduate student, Department of 

 Electrical Engineering, North Dakota State University. 



The use of a digital computer was made possible 

 through the cooperative agreement between North 

 Dakota State University, Fargo, and the Metabolism 

 and Radiation Research Laboratory, Agricultural Re- 

 search Service. 



2 Knipling, E. F. some basic principles in insect 

 population suppression. Ent. Soc. Amer. Bui. 12: 7- 

 15. 1966. 



Other models were presented by Berryman 3 

 and Lawson. 4 



In some instances we may be able to con- 

 stitute a release strain with a dominant con- 

 ditional lethal trait. Such a lethal trait would 

 provide an additional mortality factor that 

 could insure the success of the eradication pro- 

 gram when sterility alone would be inadequate 

 to completely suppress the population. We have 

 shown in considerable detail how such condi- 

 tional lethal traits under monofactorial or poly- 

 genic control could be used if partially sterile 

 males and females were released. 5 6 



3 Berryman, A. A. mathematical description of 

 the sterile-male principle. Canad. Ent. 99: 858- 

 865. 1967. 



4 Lawson, F. R. theory of control of insect popu- 

 lations by sexually sterile males. Ent. Soc. Amer. 

 Ann. 60: 713-722. 1967. 



5 Klassen, W., Creech, J. F., and Bell, R. A. the 

 potential for genetic suppression of insect popula- 

 tions BY THEIR ADAPTATIONS TO CLIMATE. U.S. Dept. 

 Agr. Misc. Pub. 1178, 77 pp. 1970. 



6 Klassen, W., Knipling, E. F., and McGuire, J. 



U. THE POTENTIAL FOR INSECT POPULATION SUPPRES- 

 SION BY DOMINANT CONDITIONAL LETHAL TRAITS. Ent. 



Soc. Amer. Ann. 63: 238-255. 1970. 



