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Mating competition between radiosterilized and normal males of fruit fly, Dacus zonatus Saunders
International Journal of Applied Radiation and Isotopes, 1973, Vol. 24, pp. 497-500. Pergamon Press. Printed in Northern Ireland
Mating Competition between Radiosterilized and Normal Males of Fruit Fly, Dacus zonatus Saunders HESHAMUL HUQUE, M. SARDAR ALAM and CH. RIAZ AHMAD Radioisotope and Radiation Laboratory, Department of Plant Protection, Ministry of Agriculture and Works, Malir Halt, Karachi-27, Pakistan (Received 16 March 1973)
Studies were carried out to evaluate the comparative mating ability between sterile and normal males of fruit fly, Dacus zonatus Saunders. Seven-day-old pupae were irradiated at 9 krad from a 6°Co source. For studying comparative mating ability of sterilized males to normal males; both were caged with normal females at the ratio of 1 : 1 : 1, 2 : 1 : 1, 4: 1 : 1, 6: 1 : 1, 8 : 1 : 1, 10 : 1 : 1, 12:1:1, 14:1 : 1 and 16:1 : 1, the percentage of viable eggs obtained at these ratios were 52, 44, 36-4, 25, 20.5, 15.5, 9.9, 2.1 and 0 per cent, respectively. But in control where there was no sterile male, 88.4 per cent of viable eggs were recorded. LA C O N C U R R E N C E P O U R L ' A C C O U P L E M E N T E N T R E LES MALES RADIOSTERILISES E T LES M,~,LES N O R M A U X DE LA M O U C H E DE F R U I T S , Dacus zonatus SAUNDERS On a fait des &udes pour 6valuer lacapabilit6 comparative pour l'aecouplement entre les tomes st6riles et les tomes normaux de la mouche des fruits Dacus zonatus Saunders. Des larvespupae ~g6es de sept jours furent irradi&s ~ 9 krad d'une source de 6°Co. Pour notre &ude, des m$1es st6rilis~s et des m~les normau.x furent encag6s avec des fenelles normales dam les proportions de 1:1:1, 2:1:1, 4:1:1, 6:1:1, 8:1:1, 10:1:I, 12:1:1, 14:1:1 et 16:1:1 alors que les proportions pour cent d'oeufs viables obtenus furent 52, 44, 36,4, 25, 20,5, 15,5, 9,9, 2,1 et 0. Cependant, dans le contr61e o~a il n'y avait aucun rome st6rile on remarqua 88,4 pour cent d'oeufs viables. HOHHYPEHUI/IH CHAPI/IBAHHH MEH{~Y PA~HO-CTEPHJII/I3I/IPOBAHHbIMH H HOPMAJII~HblMH CAMUAMH HJIO~(OBBIX MVX, D a c u s z o n a t u s CAYH~EPCA CO05II~eHM HCCJIO~OBaHHH ~JIH oI~eHHH CpaBHHTe~I, HOI~ CIIOC06HOCTH cHapHBaHHH cTepHJIbHBIX H HopMaJIBHBIX caMI~OB HJI0~OBBIX MyX D a c ~ z o n a t ~ Saunders. H8 HCTOHHHHa s o c o
06JIyqeHbI ~yHoJmH BoapacTa B 7 ~Hefl npH 9 I~H~opeHTreH. ~Jm ~ay~eH~a cpa~HHTea~HO~ CII0C05HOCTH cIlapHsaHl~I HX noera~eH~ caMw~ ofie~x ~ n o B B I~JIeTI~ax C CaMI~aMH npH C00THomeHHH 1:1:1, 2 : 1 : 1 , 4 : 1 : 1 , 6:1:1, 8 : 1 : 1 , 10:1:1, 12:1:1, 14:1:1 H 16:1:1, npHqeM HO~HqeCTBO~SHecn0coSHI~rX HHI~OB--52; 44 ; 36,4; 25 ; 20,5 ; 15,5 ; 9,9 ; 2,1 ~ 0 % COOTBeTCTBeHHO~ a 8aHHCaH 88,4~o mHaHecri0CO6HHX HHI~0B IIpH ROHTpOJ~e B 0TCyTCTBHH cTepHJ~BH~X CaMI~OB.
PAARUNGSWETTBEWERB ZWISCHEN S T R A H L E N S T E R I L I S I E R T E N UND N O R M A L E N MANNCHEN DER F R U C H T F L I E G E , Daeus zonatus SAUNDERS Studien wurden unternommen, um die vergleichsweise Paarungsf'ahigkeit zwischen sterilen und normalen Mfinnchen der Fruchtfliege, Dacus zonatus Saunders zu bestilnmen. Sieben Tage alte Puppen wurden bei 9 kr yon einer °°Co Quelle bestrahlt. Zum Studium der vergleichsweisen Paarungsfiihigkeit yon sterilisierten und normalen Miinnchen wurden bei de mit normalen Weibchen im Verh/iltnis yon 1 : I : 1 , 2:1:1, 4:1:1, 6:1:1, 8 : 1 : I , 10:I:1, 12:1:1, 14:1:1 und 16:1:1 in Kiifige eingesperrt. Der bei diesen Verhiiltnissen erhaltenc Prozentsatz an ]ebensf'~ihigen Eiern betrug32; 44; 36,4; 25; 20,5; 15,5; 9,9; 2,1 und0~o. I n den Vergleichsversuchen, wo keine sterile M~innchen zugegen waren, wurden 88,4 ~o an lebensfiihigen Eiern festgesteIlt. 497
498
Hesharaul Huque, M. Sardar Alam and Ch. Riaz. Ahmad
INTRODUCTION THE PRODUCTION of dominant lethal genes by ionizing radiation with the resultant reduction of offspring has opened a new technique of insect control. T h e sterile-male release technique was developed by BUSHLAND and HoPKINS,(2'3) KNIPLING {8'9} a n d BAUMHOVER et al., nJ who used this principle to control the screwworm, Callitroga hominivorax Coquerel. Encouraging results were obtained in Hawaii and Mexico with polygamous fruit flies treated with gamma radiation. Several other workers have reported encouraging results in their efforts to control various species of fruit-flies through this technique. KATIYAR{7) reported that pupae of fruitflies (Ceratitiscapitata) when exposed to 10-13 krad from a Cs-137 source, developed sterility in adult stages without showing any deleterious effect on longevity and mating behaviour of the flies. STmNER et al. {x~) found 10-12 krad (from 415c-e°Co) as the minimum dose to prevent egg laying as well as to avoid the production of sperms during the life cycle of the three species of fruit flies Dacus dorsalis, Ceratitis capitata and Dacuscucurbitae. MSLIS and BAC~TTX,¢10)however, reported that exposure of 8-12 krad of gammarays caused sterilization in Dacus oleae. HuQu~. and A~MADc4) and HuQu~. and Ik~-ALIK~5) have reported that Dacus cucurbita~ and Dacus zonatus can be sterilized at a dose of 7-9 krad; on the other hand HuQu~. and AZaMAD¢4} also reported that the minimum dose required to render the males of Dacus ¢iliatus fruit fly incapable of fertilizing females was 8.5-10 krad when radiated in the late pupal stage. One of the criteria for the success of this technique is that the sterilized male may compete favourably with the non-sterilized males. T o achieve this end it is essential that the sterilizing dose of radiation does not significantly impair the sexual vigour or the longevity of the treated insects. T h e results of preliminary study to evaluate the mating competition by males of Dacus zonatus irradiated at 9 krad are presented in this paper. M A T E R I A L AND M E T H O D S Pupae of Dacus zonatus were obtained from laboratory culture reared on guava pulp under
controlled temperature (3204 - 2°C) and relative humidity (55 4- 5 per cent). Same conditions were maintained during observations. Healthy and normal sized pupae were selected out and kept in plastic jars containing 2-3 70 moist sand. Six- to seven-day-old pupae were irradiated at 9 krad from a 6°Co source of 882.4 Ci emitting a central dose rate of 145,188 r/hr. T h e treated pupae were again kept in plastic jars containing moist sand to obtain virgin males. T h e emergent flies were separated sex-wise to avoid prior mating and supplied with diet comprising of yeast-hydrolysate, honey, sugar and water. T h e combination of treated and untreated males with untreated females was made within 2-4 hr after the emergence. For studying their competitive mating ability to normal males, the sterilized males were caged with normal males and normal females at the ratio o f 0 : 1 : 1, 1:1:1, 2 : 1 : 1 , 4:1:1, 6 : 1 : 1 , 8:1:1, 10:1:1, 12:1:1, 14:1:1, and 16:1:1. Five replications were used for each ratio. Observations on the percentage of viable eggs produced were made 16 days after cross mating. T o obtain eggs for counting, one dome of thick paraffin wax with ready made punctures was used per cage for oviposition (Fig. 1). The dome was sealed to a slip of glass by gently heating the glass on hot plate. Before sealing the glass a small wad of water-soaked cotton was placed under the paraffin dome. T h e glass slip with the dome was fastened with adhesive tape to the front glass of the cage (Figs. 2 and 3). T h e females laid eggs in holes already punctured for oviposition. T h e paraffin domes were placed in the cages each morning and were removed in the afternoon. This short period for oviposition was made to narrow the range of hatching. T h e eggs from the domes were collected by dipping the domes into distilled water. The dislodged eggs fell to the bottom of the beaker. Excess water was decanted off, and the eggs with a little water were transferred into large petri dishes. These eggs were then individually removed to a moist filter paper by fine camel hair brush. T h e larvae which hatched out after an incubation period of 24-35 hr at 32°C were placed in grooves made in the medium. After
Mating competition between radio-sterilized and normal males offruit fly, Dacus zonatus Saunders TABLE 1.
Progeny produced with radiosterilized males ofDacus zonatus Saunders cross mated with normal males and females at different ratios.
Cross ratio OO(T) : O O ( U T ) : Total Experiment No. OO(UT) cages No. eggs lald 1 2 3 4 5 6 7 8 9 10 I1
499
0:1 : 1 l:l:l 1: 1 : 1 2:1 : 1 4:1 : 1 6:1 : I 8:1 : I 10:1 : 1 12:1 : 1 14:1 : 1 16:1 : 1
5 5 5 5 5 5 5 5 5 5 5
Eggs hatched Pupae recovered Adults emerged in ~o age in ~o age in ~o age
12,398 8441 11,185 12,401 10,987 12,517 12,019 9581 10,713 10,501 7253
(%)
(%)
(%)
88.4 0 52 44 36.4 25 20.5 15.5 9.9 "2.1 *0
86 0 89 41 35.5 24 19 15 5 1 0
85.5 0 48 40 35 23.7 18.5 14 3.9 0 0
* Significant at 5 per cent level. entering the m e d i u m the larvae disappear. After 7 - 9 days, the larvae tunnelled their w a y out to the surface o f the m e d i u m a n d pupate. P u p a e were collected daily a n d kept in plastic jars containing 2-3~o moist sand for adult emergence. RESULTS AND DISCUSSIONS I t was observed t h a t an exposure o f 9 k r a d to Dacus zonatus resulted in decrease o f percentage o f viable eggs with the increase o f irradiated males (Table 1, Fig. 4). T h e estimated overflooding ratio of 16 : 1 : 1 o f sterile males, n o r m a l males a n d females was f o u n d most effective in the cage trials. A t this ratio the treated males m a t e d favourably with u n t r e a t e d females, b u t the resulting eggs were not viable, whereas in control 88.4 per cent o f viable eggs were obtained. N o significant reduction in the viability of egg was recorded at the m a t i n g ratios o f 1:1:1-12:1:1. However, at the ratio o f 1 4 : 1 : 1 , the percentage o f non-viable eggs was as high as 97.9 per cent a n d only 1 per cent pupate. T h e p u p a e thus formed failed to develop into adults. MELIS a n d BACETTI(1°) reported complete control o f Dacus oleae Gmelin in laboratory trials at the ratio of 4 : 1 , RHODES et al. (11) also reported great reduction in fertility of M e x i c a n fruit fly at the ratios o f 1 : 1 - 5 0 : 1 , a n d almost complete infertility at the 50:1 ratio. STEINER et al. (1~) observed that in two generations the reproductive potential o f Ceratitis capitata fruit
I00
-
90
~a 80
70
60 .o
._o >
50
"a g
'40
30
2C
IC
0 0:1 I:l 2:1 4:1 6:1 8:1 I0:112:114:1 16:1 Ratio
of irradiated
and non i r r a d i a t e d m a l e s
Fro. 4 fly can be suppressed b y 92 per cent at the ratios o f 7 . 5 : 2 0 : 1 . W h e n E u r o p e a n corn borers (Ostrinia nubilalis H u b n e r ) were caged at a ratio o f eight treated males to four untreated males a n d eight untreated females only 3.9 per cent o f eggs could hatch. (xS) I n the present studies it has been observed that sterile males
500
Heshamul Huque, M. Sardar Alam and Ch. Riaz Ahmad
can favourably compete with n o r m a l males at the ratio o f 16:1 for the successful control in the laboratory. However, the ratio of 14:1 o f sterile males a n d n o r m a l males can also be considered as a significant factor for population depletion.
REFERENCES 1. BAUMHOVERA. H., GRAHAMA. J., BITTERB. A., HoPKinS D. E., NEw W. D., DUDLEYF. H. and BUSHLAm) P,. C. d. econ. Entomol. 48, 642 (1955). 2. Busm.A_m) R. C. and HoPIClNS D. E. or. econ. Entomol. 44, 725 (1951). 3. BUSI-ILANDR. C. and HoelclNS D. E. d. econ. Entomol. 46, 648 (1953). 4. HuO.uE H. and AHMAD. H. Fd Irrad. 6, A28 (1966). 5. HuQu~ H. and MALII
6. HuQuE H. and AI~MADC. R. Int. J. appl. Radiat. Isotopes 20, 791 (1969). 7. KATIYAR K. 4th Inter-American Symposium on the
8. 9. 10. 11. 12. 13.
Peaceful Application
of
Nuclear Energy,
Mexico City, 9-13th April 1962, pp. 211217. Pan American Union, Washington, D.C. (1962). KNIPr.mo E. F. J. econ. Entomol. 48, 459 (1955). KmPLmO E. F. Ann. Rept. Smithson. Inst. pp. 409-420 (1958). MELIS A. and BAC~TTI B. Redia 45, 192 (1960). (In Italian, with English Summary.) R~olms R. H., EGUlSA F., LopEz D. F. and TEIJCI~ C . J . J . econ. Entomol. 54, 202 (1961). Sangn~ER L. F., MITCnELT W. C. and BAUerHOVER A. H. Int. J. appI. Radiat. Isotopes 13, 427 (1962). WALKER J. R. and BRINVLEY T. A. J. econ. Entomol. 56 522 (1963).
Mating Competition between Radiosterilized and Normal Males of Fruit Fly, Dacus zonatus Saunders HESHAMUL HUQUE, M. SARDAR ALAM and CH. RIAZ AHMAD Radioisotope and Radiation Laboratory, Department of Plant Protection, Ministry of Agriculture and Works, Malir Halt, Karachi-27, Pakistan (Received 16 March 1973)
Studies were carried out to evaluate the comparative mating ability between sterile and normal males of fruit fly, Dacus zonatus Saunders. Seven-day-old pupae were irradiated at 9 krad from a 6°Co source. For studying comparative mating ability of sterilized males to normal males; both were caged with normal females at the ratio of 1 : 1 : 1, 2 : 1 : 1, 4: 1 : 1, 6: 1 : 1, 8 : 1 : 1, 10 : 1 : 1, 12:1:1, 14:1 : 1 and 16:1 : 1, the percentage of viable eggs obtained at these ratios were 52, 44, 36-4, 25, 20.5, 15.5, 9.9, 2.1 and 0 per cent, respectively. But in control where there was no sterile male, 88.4 per cent of viable eggs were recorded. LA C O N C U R R E N C E P O U R L ' A C C O U P L E M E N T E N T R E LES MALES RADIOSTERILISES E T LES M,~,LES N O R M A U X DE LA M O U C H E DE F R U I T S , Dacus zonatus SAUNDERS On a fait des &udes pour 6valuer lacapabilit6 comparative pour l'aecouplement entre les tomes st6riles et les tomes normaux de la mouche des fruits Dacus zonatus Saunders. Des larvespupae ~g6es de sept jours furent irradi&s ~ 9 krad d'une source de 6°Co. Pour notre &ude, des m$1es st6rilis~s et des m~les normau.x furent encag6s avec des fenelles normales dam les proportions de 1:1:1, 2:1:1, 4:1:1, 6:1:1, 8:1:1, 10:1:I, 12:1:1, 14:1:1 et 16:1:1 alors que les proportions pour cent d'oeufs viables obtenus furent 52, 44, 36,4, 25, 20,5, 15,5, 9,9, 2,1 et 0. Cependant, dans le contr61e o~a il n'y avait aucun rome st6rile on remarqua 88,4 pour cent d'oeufs viables. HOHHYPEHUI/IH CHAPI/IBAHHH MEH{~Y PA~HO-CTEPHJII/I3I/IPOBAHHbIMH H HOPMAJII~HblMH CAMUAMH HJIO~(OBBIX MVX, D a c u s z o n a t u s CAYH~EPCA CO05II~eHM HCCJIO~OBaHHH ~JIH oI~eHHH CpaBHHTe~I, HOI~ CIIOC06HOCTH cHapHBaHHH cTepHJIbHBIX H HopMaJIBHBIX caMI~OB HJI0~OBBIX MyX D a c ~ z o n a t ~ Saunders. H8 HCTOHHHHa s o c o
06JIyqeHbI ~yHoJmH BoapacTa B 7 ~Hefl npH 9 I~H~opeHTreH. ~Jm ~ay~eH~a cpa~HHTea~HO~ CII0C05HOCTH cIlapHsaHl~I HX noera~eH~ caMw~ ofie~x ~ n o B B I~JIeTI~ax C CaMI~aMH npH C00THomeHHH 1:1:1, 2 : 1 : 1 , 4 : 1 : 1 , 6:1:1, 8 : 1 : 1 , 10:1:1, 12:1:1, 14:1:1 H 16:1:1, npHqeM HO~HqeCTBO~SHecn0coSHI~rX HHI~OB--52; 44 ; 36,4; 25 ; 20,5 ; 15,5 ; 9,9 ; 2,1 ~ 0 % COOTBeTCTBeHHO~ a 8aHHCaH 88,4~o mHaHecri0CO6HHX HHI~0B IIpH ROHTpOJ~e B 0TCyTCTBHH cTepHJ~BH~X CaMI~OB.
PAARUNGSWETTBEWERB ZWISCHEN S T R A H L E N S T E R I L I S I E R T E N UND N O R M A L E N MANNCHEN DER F R U C H T F L I E G E , Daeus zonatus SAUNDERS Studien wurden unternommen, um die vergleichsweise Paarungsf'ahigkeit zwischen sterilen und normalen Mfinnchen der Fruchtfliege, Dacus zonatus Saunders zu bestilnmen. Sieben Tage alte Puppen wurden bei 9 kr yon einer °°Co Quelle bestrahlt. Zum Studium der vergleichsweisen Paarungsfiihigkeit yon sterilisierten und normalen Miinnchen wurden bei de mit normalen Weibchen im Verh/iltnis yon 1 : I : 1 , 2:1:1, 4:1:1, 6:1:1, 8 : 1 : I , 10:I:1, 12:1:1, 14:1:1 und 16:1:1 in Kiifige eingesperrt. Der bei diesen Verhiiltnissen erhaltenc Prozentsatz an ]ebensf'~ihigen Eiern betrug32; 44; 36,4; 25; 20,5; 15,5; 9,9; 2,1 und0~o. I n den Vergleichsversuchen, wo keine sterile M~innchen zugegen waren, wurden 88,4 ~o an lebensfiihigen Eiern festgesteIlt. 497
498
Hesharaul Huque, M. Sardar Alam and Ch. Riaz. Ahmad
INTRODUCTION THE PRODUCTION of dominant lethal genes by ionizing radiation with the resultant reduction of offspring has opened a new technique of insect control. T h e sterile-male release technique was developed by BUSHLAND and HoPKINS,(2'3) KNIPLING {8'9} a n d BAUMHOVER et al., nJ who used this principle to control the screwworm, Callitroga hominivorax Coquerel. Encouraging results were obtained in Hawaii and Mexico with polygamous fruit flies treated with gamma radiation. Several other workers have reported encouraging results in their efforts to control various species of fruit-flies through this technique. KATIYAR{7) reported that pupae of fruitflies (Ceratitiscapitata) when exposed to 10-13 krad from a Cs-137 source, developed sterility in adult stages without showing any deleterious effect on longevity and mating behaviour of the flies. STmNER et al. {x~) found 10-12 krad (from 415c-e°Co) as the minimum dose to prevent egg laying as well as to avoid the production of sperms during the life cycle of the three species of fruit flies Dacus dorsalis, Ceratitis capitata and Dacuscucurbitae. MSLIS and BAC~TTX,¢10)however, reported that exposure of 8-12 krad of gammarays caused sterilization in Dacus oleae. HuQu~. and A~MADc4) and HuQu~. and Ik~-ALIK~5) have reported that Dacus cucurbita~ and Dacus zonatus can be sterilized at a dose of 7-9 krad; on the other hand HuQu~. and AZaMAD¢4} also reported that the minimum dose required to render the males of Dacus ¢iliatus fruit fly incapable of fertilizing females was 8.5-10 krad when radiated in the late pupal stage. One of the criteria for the success of this technique is that the sterilized male may compete favourably with the non-sterilized males. T o achieve this end it is essential that the sterilizing dose of radiation does not significantly impair the sexual vigour or the longevity of the treated insects. T h e results of preliminary study to evaluate the mating competition by males of Dacus zonatus irradiated at 9 krad are presented in this paper. M A T E R I A L AND M E T H O D S Pupae of Dacus zonatus were obtained from laboratory culture reared on guava pulp under
controlled temperature (3204 - 2°C) and relative humidity (55 4- 5 per cent). Same conditions were maintained during observations. Healthy and normal sized pupae were selected out and kept in plastic jars containing 2-3 70 moist sand. Six- to seven-day-old pupae were irradiated at 9 krad from a 6°Co source of 882.4 Ci emitting a central dose rate of 145,188 r/hr. T h e treated pupae were again kept in plastic jars containing moist sand to obtain virgin males. T h e emergent flies were separated sex-wise to avoid prior mating and supplied with diet comprising of yeast-hydrolysate, honey, sugar and water. T h e combination of treated and untreated males with untreated females was made within 2-4 hr after the emergence. For studying their competitive mating ability to normal males, the sterilized males were caged with normal males and normal females at the ratio o f 0 : 1 : 1, 1:1:1, 2 : 1 : 1 , 4:1:1, 6 : 1 : 1 , 8:1:1, 10:1:1, 12:1:1, 14:1:1, and 16:1:1. Five replications were used for each ratio. Observations on the percentage of viable eggs produced were made 16 days after cross mating. T o obtain eggs for counting, one dome of thick paraffin wax with ready made punctures was used per cage for oviposition (Fig. 1). The dome was sealed to a slip of glass by gently heating the glass on hot plate. Before sealing the glass a small wad of water-soaked cotton was placed under the paraffin dome. T h e glass slip with the dome was fastened with adhesive tape to the front glass of the cage (Figs. 2 and 3). T h e females laid eggs in holes already punctured for oviposition. T h e paraffin domes were placed in the cages each morning and were removed in the afternoon. This short period for oviposition was made to narrow the range of hatching. T h e eggs from the domes were collected by dipping the domes into distilled water. The dislodged eggs fell to the bottom of the beaker. Excess water was decanted off, and the eggs with a little water were transferred into large petri dishes. These eggs were then individually removed to a moist filter paper by fine camel hair brush. T h e larvae which hatched out after an incubation period of 24-35 hr at 32°C were placed in grooves made in the medium. After
Mating competition between radio-sterilized and normal males offruit fly, Dacus zonatus Saunders TABLE 1.
Progeny produced with radiosterilized males ofDacus zonatus Saunders cross mated with normal males and females at different ratios.
Cross ratio OO(T) : O O ( U T ) : Total Experiment No. OO(UT) cages No. eggs lald 1 2 3 4 5 6 7 8 9 10 I1
499
0:1 : 1 l:l:l 1: 1 : 1 2:1 : 1 4:1 : 1 6:1 : I 8:1 : I 10:1 : 1 12:1 : 1 14:1 : 1 16:1 : 1
5 5 5 5 5 5 5 5 5 5 5
Eggs hatched Pupae recovered Adults emerged in ~o age in ~o age in ~o age
12,398 8441 11,185 12,401 10,987 12,517 12,019 9581 10,713 10,501 7253
(%)
(%)
(%)
88.4 0 52 44 36.4 25 20.5 15.5 9.9 "2.1 *0
86 0 89 41 35.5 24 19 15 5 1 0
85.5 0 48 40 35 23.7 18.5 14 3.9 0 0
* Significant at 5 per cent level. entering the m e d i u m the larvae disappear. After 7 - 9 days, the larvae tunnelled their w a y out to the surface o f the m e d i u m a n d pupate. P u p a e were collected daily a n d kept in plastic jars containing 2-3~o moist sand for adult emergence. RESULTS AND DISCUSSIONS I t was observed t h a t an exposure o f 9 k r a d to Dacus zonatus resulted in decrease o f percentage o f viable eggs with the increase o f irradiated males (Table 1, Fig. 4). T h e estimated overflooding ratio of 16 : 1 : 1 o f sterile males, n o r m a l males a n d females was f o u n d most effective in the cage trials. A t this ratio the treated males m a t e d favourably with u n t r e a t e d females, b u t the resulting eggs were not viable, whereas in control 88.4 per cent o f viable eggs were obtained. N o significant reduction in the viability of egg was recorded at the m a t i n g ratios o f 1:1:1-12:1:1. However, at the ratio o f 1 4 : 1 : 1 , the percentage o f non-viable eggs was as high as 97.9 per cent a n d only 1 per cent pupate. T h e p u p a e thus formed failed to develop into adults. MELIS a n d BACETTI(1°) reported complete control o f Dacus oleae Gmelin in laboratory trials at the ratio of 4 : 1 , RHODES et al. (11) also reported great reduction in fertility of M e x i c a n fruit fly at the ratios o f 1 : 1 - 5 0 : 1 , a n d almost complete infertility at the 50:1 ratio. STEINER et al. (1~) observed that in two generations the reproductive potential o f Ceratitis capitata fruit
I00
-
90
~a 80
70
60 .o
._o >
50
"a g
'40
30
2C
IC
0 0:1 I:l 2:1 4:1 6:1 8:1 I0:112:114:1 16:1 Ratio
of irradiated
and non i r r a d i a t e d m a l e s
Fro. 4 fly can be suppressed b y 92 per cent at the ratios o f 7 . 5 : 2 0 : 1 . W h e n E u r o p e a n corn borers (Ostrinia nubilalis H u b n e r ) were caged at a ratio o f eight treated males to four untreated males a n d eight untreated females only 3.9 per cent o f eggs could hatch. (xS) I n the present studies it has been observed that sterile males
500
Heshamul Huque, M. Sardar Alam and Ch. Riaz Ahmad
can favourably compete with n o r m a l males at the ratio o f 16:1 for the successful control in the laboratory. However, the ratio of 14:1 o f sterile males a n d n o r m a l males can also be considered as a significant factor for population depletion.
REFERENCES 1. BAUMHOVERA. H., GRAHAMA. J., BITTERB. A., HoPKinS D. E., NEw W. D., DUDLEYF. H. and BUSHLAm) P,. C. d. econ. Entomol. 48, 642 (1955). 2. Busm.A_m) R. C. and HoPIClNS D. E. or. econ. Entomol. 44, 725 (1951). 3. BUSI-ILANDR. C. and HoelclNS D. E. d. econ. Entomol. 46, 648 (1953). 4. HuO.uE H. and AHMAD. H. Fd Irrad. 6, A28 (1966). 5. HuQu~ H. and MALII
6. HuQuE H. and AI~MADC. R. Int. J. appl. Radiat. Isotopes 20, 791 (1969). 7. KATIYAR K. 4th Inter-American Symposium on the
8. 9. 10. 11. 12. 13.
Peaceful Application
of
Nuclear Energy,
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