APPLICATION OF STERILIZATION TECHNIQUES FOR 
CONTROLLING AND ERADICATING INSECT PESTS 
L.D. Christenson, 
Entomology Research Division, Agricultural Research Service, 
U.S, Department of Agriculture, Beltsville, Md. 
Few animal species can tolerate a drastic 
reduction in their reproductive potential that 
at best may be only high enough to outweigh 
the natural hazards present in their environ- 
ment. When sterility can be inducedin animals 
without destroying mating competitiveness and 
these sterile individuals can then be introduced 
into the natural environments in overwhelming 
numbers during a sustained period, the natural 
population subjected to such treatment will in 
due time vanish. 
About 1937, E, F. Knipling, of the U.S. 
Department of Agriculture, developed a unique 
new method for population suppression that 
was based on this concept. Since 1937, the 
method has passed beyond the hypothesis stage 
and demonstrated its effectiveness against 
populations of the screw-worm fly (Cochliomyia 
hominivorax (Coquerel)), the melon fly (Dacus 
cucurbitae (Coquillett)), the oriental fruit fly 
(Dacus dorsalis (Hendel)), the Mediterranean 
fruit fly (Ceratitis capitata (Wiedemann)), and 
the Mexican fruit fly (Anastrepha ludens 
(Loew)). This new approach to insect control-- 
the sterile insect release method--must rank 
as one of the most remarkable biological 
achievements of our time. 
The principles involved in the sterile male 
release method have been documented in nu- 
merous publications, the most recent andcom- 
prehensive of which is by Dr. Knipling.1 In the 
present discussion I will emphasize 
recent progress in practical applications of the 
technique for controlling populations of certain 
insects. 
As early as 1937, it occurred to Dr, Knipling 
that it might be economically feasible to rear 
and release sterilized screw-worm flies in 
sufficient numbers to exceed the natural popu- 
lation. A colleague, A. W. Lindquist, then 
: Knipling, E, F, The potential role of the sterility 
method for insect population control with special 
references to combining this method with conventional 
methods, U.S, Dept. Agr. ARS 33-98, 1964, 
95 
located at Uvalde, Tex., had observed that the 
numbers of screw-worm flies were exceedingly 
small in that area during the winter. Several 
methods for using released flies to destroy 
their own kind were then considered. The most 
promising approach seemed to be the release 
of flies sterilized with X- or gamma rays. 
During the next 12 years, the reactions of 
biologists to this self-destruction approach 
to screw-worm control were generally pessi- 
mistic, Notwithstanding, the possibilities, as 
based on theoretical calculations, continued to 
be too great to ignore. Consequently, in 1950, 
with encouragement from H. J. Muller--an 
eminent geneticist formerly with the University 
of Texas, but later with Indiana University-- 
research to explore the sterility concept of 
insect population control was begun on the 
screw-worm fly. This research was conducted 
under the leadership of R. C. Bushland of 
the Entomology Research Division. The first 
studies dealt with the effects of X- andgamma 
rays on the reproductive behavior and potential 
of the insect. 
When news of the screw-worm sterilization 
research in Texas reached Hawaii, where 
I was then studying tropical fruit flies, I was 
greatly impressed with the possibilities of 
utilizing sterile insects tocontrol wildinsects. 
Already we had advanced far in our knowledge 
of how to mass-rear fruit flies and could 
produce large quantities of these flies at low 
cost. Even though the early concept of the 
sterile male release method suggested that it 
would apply only to species that mate but once, 
theoretically at least, it seemed possible that 
grossly overflooding the wild polygamous 
tropical fruit flies with sterile insects might 
have a chance of effectively eliminating the 
flies, Insect species often undergo stress con- 
ditions that require the product of their full 
reproductive potential. Our thought was that 
an added burden of induced sterility would 
make it difficult for the fruit flies to survive 
critical periods. On this basis we began our 
