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Three populations of C. mbila originating from the rain forest (Ibadan), southern part of sudan savanna (Kadawa, Kano) and the Jos Plateau, and C. triangula population from Ibadan (Moor Plantation) were compared in relation to their ability to acquire and transmit maize streak virus (MSV). Acquisition and transmission efficiency increased with time of access feeding. Joint regression analysis showed that the populations did not differ significantly from each other in transmission efficiency of the virus. Nymphs and adults of some populations acquired MSV in 30 sec and adults transmitted the virus during the 2-hr inoculation access. Efficiency of virus transmission generally increased with acquisition or inoculation time.The minimum latent period of maize streak virus in the various Cicadulina populations was 14-18 hr and the medium latent period (LP 50) was 16-20 hr. Some individuals in all populations retain the virus throughout their lives.Since the various Cicadulina populations were largely similar in their ability to acquire and transmit the virus into healthy maize, other factors which might be implicated in the epidemiology of maize streak disease are discussed.

Significant differences in nymphal development period and fecundity were observed between five populations of Cicadulina mbila (Naudé) and C. triangula Ruppel from three climatic zones in Nigeria: rain forest (Ibadan), southern part of Sudan savanna (Kadawa, Kano) and the Jos Plateau. The C. triangula population that is used in mass rearing for resistance screening at the International Institute of Tropical Agriculture (IITA), Ibadan, developed much more rapidly than the wild C. triangula population from Ibadan. Similarly, the C. mbila population from the Kadawa Irrigation Scheme, Kano, developed more rapidly than the population from the Jos Plateau. All Cicadulina populations were 3–4 times as prolific on pearl millet as on maize, sorghum or the grass Digitaria exilis. The IITA colony of C. triangula was significantly more fecund than C. mbila. It is clear that Cicadulina species and populations with high reproductive potential would be most suitable for mass rearing for resistance screening to the maize streak virus disease.

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The control of pest populations through the manipulation of their genetic component or mechanism of inheritance is becoming increasingly important. Two of the most promising genetic methods for the control of lepidopteran insects are inherited or F J and hybrid sterility.To induce F t sterility in C. partellus, male pupae were irradiated with various doses of gamma radiation (0-15 krad) and emerging adults of normal appearance were used in crosses with normal females. The ¥ l progeny were reared on artificial diet and the resulting adult males were crossed with unirradiated females to give F 2 , the process being repeated until F 5 progeny were obtained. For each generation lifespan of males, oviposition, egg hatchability and sex ratio were carefully recorded. The results showed that females mated with irradiated males oviposited significantly fewer eggs than normal and that this phenomenon was perpetuated over several generations. Hatchability of eggs laid by females mated to irradiated males or male progeny was significantly lower than that of the controls and sex ratio was distorted slightly in favour of males in all generations observed. The lower oviposition, lower egg hatch, distortion of sex ratio in favour of males and the apparent persistence of sterility over several generations offer the potential of inherited sterility for the control of C. partellus.Resume-L'utilisation des manipulations genetiques et des mecanismes d'heredite, comme moyens de lutte contre les ravageurs de cultures devient de plus en plus importante. La sterility he'rite'e ou sterilite en F ; sont les deux methods les plus promettantes.Pour induire la sterilite en F 1 chez C. partellus males, des pupes ont ete exposes a des doses varied de rayons gamma (0-15 krad), les adultes d'apparence normale qui ont emerges ont ete croises avec des femelles norm ales. La generation .F l obtenue a ete eleve sur un milieu de culture artificiel et ses adultes males ont ete croises une fois de plus avec des femelles norm ales produisant ainsi la generation F 2 . Cet exercise a ete repete jusqu'a l'obtension de la generation F,. Pour chacune des generations la duree de vie des males, l'oviposition, l'eclosion des oeufs et le taux sexuel ont ete soigneusement enregistres. Les resultats ont montre que les femelles croisles avec des males irradies pondaient peu d'oeufs par rapport a la normale et que ce phenomene se repetait sur plusieurs generations. D'autre part l'eclosion des oeufs ainsi obtenus a ete significativement plus basse que celle des contrdles et le taux sexuel change legerement en faveur des males dans toutes les generations observees. La baisse de l'oviposition, de l'eclosion des oeufs, la modification du taux sexuel en faveur des males et la persistance apparente de la sterilite sur plusieurs •Present address: Namulonge Research Station, P. O. Box 7084, Kampala, Uganda. 713 714 V. A. O. OKOTH generations contribuent a la sterilite heritee qui est un moyen potentiel de lutte contre C. partellus.