Hostname: page-component-76fb5796d-5g6vh Total loading time: 0 Render date: 2024-04-25T10:39:28.969Z Has data issue: false hasContentIssue false
  • English
  • Français

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
Get access Rights & Permissions [Opens in a new window]

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

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Beevor, P. S., Hall, D. R., Lester, R., Poppi, R. G., Read, J. S. & Nesbitt, B. F. (1975). Sex pheromones of the armyworm moth, Spodoptera exempta (Walk.).—Experientia 31, 22–23.CrossRefGoogle Scholar
Betts, E. (1976). Forecasting infestations of tropical migrant pests: the desert locust and the African armyworm.—pp. 113–134 in Rainey, R. C. (Ed.). Insect flight.—287 pp. Oxford, Blackwell Scientific (Symp. R. Ent. Soc. Lond. no. 7).Google Scholar
Den Boer, P. J. (1968). Spreading of risks and stabilization of animal numbers.—Acta biotheor. 18, 165–194.CrossRefGoogle ScholarPubMed
Brown, E. S. & Odiyo, P. (1968). The rate of feeding of the African armyworm Spodoptera exempta (Walk.) and its significance for control operations.—E. Afr. agric. For. J. 33, 245–256.CrossRefGoogle Scholar
Brown, E. S., Betts, E. & Rainey, R. C. (1969). Seasonal changes in distribution of the African armyworm, Spodoptera exempta (Wlk.) (Lep., Noctuidae), with special reference to eastern Africa.—Bull. ent. Res. 58, 661–728.CrossRefGoogle Scholar
Dingle, H. (1979). Adaptive variation in the evolution of insect migration.—pp. 64–87 in Rabb, R. L. & Kennedy, G. G. (Eds.). Movement of highly mobile insects: concepts and methodology in research.—456 pp. Raleigh, North Carolina State University.Google Scholar
Faure, J. C. (1943). Phase variation in the armyworm, Laphygma exempta (Walk.).—Sci. Bull. Dep. Agric. For. Un. S. Afr. no. 234, 17 pp.Google Scholar
Jacques, R. P. (1977). Stability of entomopathogenic viruses.—pp. 100–103 in Ignoffo, C. M. & Hostetter, D. L. (Eds.). Environmental stability of microbial insecticides.—Misc. Publs ent. Soc. Am. 10.Google Scholar
Khasimuddin, S. (1981a). Behavioural ecology of the African armyworm, Spodoptera exempta (Walker): observations on population processes during a high-density outbreak.—Insect Sci. Applic. 1, 143–146.Google Scholar
Khasimuddin, S. (1981b). Phase variation and ‘off-season’ survival of the African armyworm, Spodoptera exempta (Walker) (Lepidoptera: Noctuidae).—Insect Sci. Applic. 1, 357–360.Google Scholar
Khasimuddin, S. & Lubega, M. C. (1979). Behavioural ecology of the African armyworm, Spodoptera exempta (Walker) (Lepidoptera: Noctuidae); evidence of successive generations from Kenya.—Bull. ent. Res. 69, 275–282.CrossRefGoogle Scholar
Matthee, J. J. (1952). The occurrence of the armyworm (Laphygma exempta (Walk)) in and around Pretoria.—J. ent. Soc. sth. Afr. 51, 122–128.Google Scholar
McKinley, D. J. (1980). The use of viruses in the control of Spodoptera species and prior safety testing.—Ecol. Bull. 31, 75–80.Google Scholar
Nyirenda, G. K. C. (1985). Persistent populations of males of the African armyworm, Spodoptera exempta (Walker) (Lepidoptera: Noctuidae), in Malawi.—Bull. ent. Res. 75, 405–415.CrossRefGoogle Scholar
Odiyo, P. O. (1981). Development of the first outbreaks of the African armyworm, Spodoptera exempta (Walk.), between Kenya and Tanzania during the ‘off-season’ months of July to December.—Insect Sci. Applic. 1, 305–318.Google Scholar
Parker, W. E. & Gatehouse, A. G. (1985a). The effect of larval rearing conditions on flight performance in females of the African armyworm, Spodoptera exempta (Walker) (Lepidoptera: Noctuidae).—Bull. ent. Res. 75, 35–47.CrossRefGoogle Scholar
Parker, W. E. & Gatehouse, A. G. (1985b). Genetic factors controlling flight performance and migration in the African armyworm, Spodoptera exempta (Walker) (Lepidoptera: Noctuidae).—Bull. ent. Res. 75, 49–63.CrossRefGoogle Scholar
Pedgley, D. E. & Rose, D. J. W. (1982). International workshop on the control of armyworm and other migrant pests in East Africa, Arusha, July 1982.—Tropical Pest Management 28, 437–440.CrossRefGoogle Scholar
Persson, B. (1981). Population fluctuations of the African armyworm, Spodoptera exempta (Walker) (Lepidoptera: Noctuidae), in outdoor cages in Kenya.—Bull, ent. Res. 71, 289–297.CrossRefGoogle Scholar
Rose, D. J. W. (1975). Field development and quality changes in successive generations of Spodoptera exempta (Walk.), the African armyworm.—J. appl. Ecol. 12, 727–739.CrossRefGoogle Scholar
Rose, D. J. W. (1979). The significance of low-density populations of the African armyworm Spodoptera exempta (Walk.).—Phil. Trans. R. Soc. (B) 287, 393–402.Google Scholar
Solbreck, C. (1978). Migration, diapause, and direct development as alternative life histories in a seed bug, Neacoryphus bicrucis.—pp. 195–217 in Dingle, H. (Ed.). Evolution of insect migration and diapause.—284 pp. New York, Springer-Verlag.Google Scholar
Southwood, T. R. E. (1975). The dynamics of insect populations.—pp. 151–199 in Pimentel, D. (Ed.). Insects, science, and society.—284 pp. New York, Academic Press.Google Scholar
Southwood, T. R. E. (1977). The relevance of population dynamic theory to pest status.—pp. 35–54 in Cherrett, J. M. & Sagar, G. R. (Eds.). Origins of pest, parasite, disease and weed problems. The 18th symposium of the British Ecological Society, Bangor, 12–14 April 1976.—413 pp. Oxford, Blackwell Scientific.Google Scholar
Stearns, S. C. (1976). Life-history tactics: a review of the ideas.—Q. Rev. Biol. 51, 3–47.CrossRefGoogle ScholarPubMed
Tucker, M. R. (1984a). Forecasting the severity of armyworm seasons in East Africa from early season rainfall.—Insect Sci. Applic. 5, 51–55.Google Scholar
Tucker, M. R. (1984b). Possible sources of outbreaks of the armyworm, Spodoptera exempta (Walker) (Lepidoptera: Noctuidae), in East Africa at the beginning of the season.—Bull. ent. Res. 74, 599–607.CrossRefGoogle Scholar
Tucker, M. R., Mwandoto, S. & Pedgley, D. E. (1982). Further evidence for windborne movement of armyworm moths, Spodoptera exempta, in East Africa.—Ecol. Entomol. 7, 463–473.CrossRefGoogle Scholar
Tucker, M. R. & Pedgley, D. E. (1983). Rainfall and outbreaks of the African armyworm, Spodoptera exempta (Walker) (Lepidoptera: Noctuidae).—Bull. ent. Res. 73, 195–199.CrossRefGoogle Scholar
Yarro, J. G. (1984). Survival and development of the African armyworm Spodoptera exempta (Walk.) (Lepidoptera, Noctuidae) on some grass species (Gramineae).—Insect Sci. Applic. 5, 1–5.Google Scholar