Possible sources of outbreaks of the armyworm, Spodoptera exempta (Walker) (Lepidoptera: Noctuidae), in East Africa at the beginning of the season

Abstract

AbstractPossible sources of adults of Spodoptera exempta (Wlk.) giving rise to outbreaks in East Africa at the beginning of the season were estimated by assuming downwind displacement and using the technique of backtracking. The accuracy of backtracks was limited by the availability of suitable weather data, but they provided a reasonably objective means of analysis. Eastern Kenya and eastern Tanzania were found to be the most likely source areas for moths. Migration from Ethiopia was very unlikely. Immigration from southern Somalia into Kenya, and from Malawi, Zambia or northern Mozambique into southern Tanzania was possible in a few years. In most years, there were likely to be sources in Kenya or Tanzania, probably of low density and in places suitable for the larvae to survive the dry season.