Effect of millet variety and date of sowing on diapause development in Coniesta ignefusalis (Hampson) in Northern Ghana

Experiments between 1996 and 1997 at the Manga Research Station in the Sudan savanna zone of Ghana on the effects of millet variety and date of sowing on the incidence of diapause in Coniesta ignefusalis showed that only the late millet variety Z aa supported C. ignefusalis larval diapause. Early millet was not important in supporting dry season survival of the insect. Delayed planting tended to increase the incidence of diapause, resulting in significantly higher numbers of diapausing larvae in millet stalks at the end of the growing season. Grain yields also declined with delayed planting. Diapausing larvae were extracted from plants of different ages during mid-November each year, suggesting that age of the host plant may not be the main factor inducing diapause development in this insect. The practical implications of these findings are discussed.