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Evidence of persistent populations of the African armyworm, Spodoptera exempta (walker) (lepidoptera: noctuidae), in east-central Tanzania

Published online by Cambridge University Press:  10 July 2009

P. J. Merrett
P. J. Merrett
Affiliation:
Overseas Development Administration of the United Kingdom Armyworm Project, P.O. Ilonga, Kilosa, TZ
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Abstract

There is a growing body of evidence to suggest that low density populations of Spodoptera exempta (Walker) in the solitary-phase can persist during the dry season in certain localities in eastern Africa. Moths were caught in simple pheromone traps for several months after the estimated dates of emergence of larval outbreaks in central Tanzania in 1980 and from 1982 to 1984. This provided evidence for the occurrence of a shifting population between the Uluguru Mountains and the swampy coastal areas, in east-central Tanzania, for a large part of the year. Central Tanzania is an important area for the development of the first outbreaks of the season in eastern Africa and for any control strategy. It has been suggested that S. exempta fits the criteria for an r-selected species. However, the low migratory capacity of low-density populations indicates rather that the species spreads out its risks in space and time. A theoretical genetic mechanism controlling the distance flown by moths may enable the species to exhibit both migratory and non-migratory strategies. Thus both ephemeral and continously favourable habitats may be exploited.

Type
Original Articles
Information
Bulletin of Entomological Research , Volume 76 , Issue 2 , June 1986 , pp. 247 - 263
Copyright
Copyright © Cambridge University Press 1986

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