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Inter- and intra-seasonal variation in outbreak distribution of the armyworm, Spodoptera exempta (Lepidoptera: Noctuidae), in eastern Africa

Published online by Cambridge University Press:  10 July 2009

M. R. Tucker
M. R. Tucker*
Affiliation:
Natural Resources Institute, Chatham, UK
*
Natural Resources Institute, Chatham Maritime, Chatham, Kent ME4 4TB, UK
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Abstract

Reports of the African armyworm, Spodoptera exempta (Walker), in eastern Africa for sixteen seasons (1972–73 to 1987–88) were analysed together with weather records to identify the most frequent locations of outbreaks and their relationships with weather. Outbreaks were classified into ‘primary’ outbreaks (derived from low density parent populations), ‘secondary’ outbreaks (derived from previous out breaks) and ‘critical’ outbreaks (leading to many subsequent outbreaks). Differences in seasonal severity of armyworm infestations in relation to the timing and location of primary outbreaks and early season rainfall were also examined. Trajectory analysis was used to estimate migrations of windborne moths, and the distribution of rainstorms was used to help estimate the timing of moth concentration leading to outbreaks of S. exempta. First reported armyworrn outbreaks from October to December in Kenya and Tanzania were usually primary. Critical primary outbreaks mostly occurred in east-central Tanzania, north-east Tanzania and the adjacent Taveta district of Kenya, and east-central Kenya. Strategic control (to prevent subsequent, downwind outbreaks) is best carried out in these areas. Migration direction was largely determined by seasonally dominant winds, although windfield disturbances were occasionally important. Three seasons in which very low numbers of S. exempta were reported, had heavy, persistent October to December rainfall leading to high larval mortality. Seasons with many outbreaks often had rainstorms separated by dry periods, during the rainy seasons.

Type
Original Articles
Information
Bulletin of Entomological Research , Volume 84 , Issue 2 , June 1994 , pp. 275 - 287
Copyright
Copyright © Cambridge University Press 1994

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References

Bowden, J. (1973) The influence of moonlight oncatches of insects in light-traps in Africa. Pt I. The moon and moonlight. Bulletin of Entomological Research 63, 113–128.Google Scholar
Bowden, J. (1982) An analysis of factors affecting catches of insects in light-traps. Bulletin of Entomological Research 72, 535–556.CrossRefGoogle Scholar
Bowden, J. & Church, B.M. (1973) The influence of moonlight on catches of insects in light-traps in Africa. Pt II. The effect of moon phase on light-trap catches. Bulletin of Entomological Research 63, 129–142.CrossRefGoogle Scholar
Brown, E.S., Betts, E. & Rainey, R.C. (1969) Seasonal changes in distribution of the African armyworm, Spodoptera exempta (WIk) (Lep. Noctuidae), with special references to eastern Africa. Bulletin Entomological Research 58, 661–728.CrossRefGoogle Scholar
Chen, R.L., Bao, X.-Z., Drake, V.A., Farrow, R.A., Wang, S.-Y., Sun, Y.J. & Zhai, B.P. (1989) Radar observations of the spring migration into north-eastern China of the oriental armyworm, Mythimna separata, and other insects. Ecological Entomology 14, 149–162.Google Scholar
East African Meterological Department (1975) Climatological statistics for east Africa. Part III. Tanzania. 92 pp. Nairobi, East African Meteorological Department.Google Scholar
Farrow, R.A. & McDonald, G. (1987) Migration strategies and outbreaks of noctuid pests in Australia. Insect Science and its Application 8, 531–542.Google Scholar
Faure, J.C. (1943) Phase variation in the armyworm Laphygma exempta (Walker). South African Science Bulletin No. 234.Google Scholar
Findlater, J. (1966) Cross-equatorial. jet streams at low level over Kenya Meteorological Magazine 95, 353–364.Google Scholar
Findlater, J. (1967) Cross-equatorial jet streams at low level over Kenya—Part II Some further evidence. Meteorological Magazine 96, 53–56.Google Scholar
Findlater, J. (1969) A major low-level current near the Indian Ocean during northern summer. Quarterly Journal of the Royal Meteorological Society 95, 362–380.Google Scholar
Gatehouse, A.G. (1986) Migration in the African armyworm Spodoptera exempta: genetic determination of migratory capacity and a new synthesis. pp. 128–144in Danthanarayana, W. (Ed.) Insect flight: dispersal and migration. Berlin, Springer Verlag.Google Scholar
Gatehouse, A.G. (1987) Migration and low population density in armyworm (Lepidoptera: Noctuidae) life histories. Insect Science and Its Application 8, 573–580Google Scholar
Haggis, M.J. (1984) Distribution, frequency of attack and seasonal incidence of the African armyworm, Spodoptera exempta (WIk.) (Lep. Noctuidae) with particular reference to Africa and southwestern Arabia. Tropical Development and Research Institute Report L69, 116 ppGoogle Scholar
Haggis, M.J. (1986) Distribution of the Africanarmyworm, Spodoptera exempta (Walker) (Lepidoptera: Noctuidae) and the frequency of larval outbreaks in Africa and Arabia. Bulletin of Entomological Research 76, 151–170.Google Scholar
Kenya Meteorological Department (1984) Climatological statistics for Kenya. 87 pp. Nairobi, Kenya Meteorological Department.Google Scholar
McNeil, J.N. (1987) The true armyworm Pseudaletia unipuncta a victim of the pied piper or a seasonal migrant? Insect Science and Its Application 8, 591–597.Google Scholar
Mitchell, E.R., McNeil, J.N., Westbrook, J.K., Silvain, J.F., Lalanne-Casson, B., Chalfont, R.B., Pair, S.D., Wadill, V.H., Sotamayor-Rios, A. & Proshold, F.I. (1991) Seasonal periodicity of fall armyworm (Lepidoptera: Noctuidae) in the Caribbean basin and northwards to Canada. Journal of Entormological Science 26, 39–50.Google Scholar
Odiyo, P.O. (1979) Forecasting infestations of a migrant pest. the African armyworm Spodoptera exempta (WIk). Philosophical Transactions of the Royal Society, London B 287, 403–413.Google 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—December. Insect Science and Its Application 1, 305–318.Google Scholar
Odiyo, P.O. (1984). A guide to seasonal changes in the distribution of armyworm infestations in East Africa Insect Science and Its Application 5, 107–119.Google Scholar
Page, W.W. (1988) Varying durations of arrested oocyte development in relation to migration in the African armyworm moth, Spodoptera exempta (Walker) (Lepidoptera: Noctuidae) Bulletin of Entomological Research 79 181–198Google Scholar
Parker, W.E. & Gatehouse, A.G. (1985a) The effect of larval rearing conditions on flight performances in females of the African armyworm, Spodoptera exempta (Walker) (Lepidoptera: Noctuidae). Bulletin of Entomological Research 75, 35–47.Google Scholar
Parker, W.E. & Gatehouse, A.G. (1985b) Genetic factors controlling flight performance and migration in the African armyworm moth, Spodoptera exempta (Walker) (Lepidoptera Noctuidae). Bulletin of Entomological Research 75, 49–63.CrossRefGoogle Scholar
Pedgley, D.E., Reynolds, D.R., Riley, J.R. & Tucker, M.R. (1982) Flying insects reveal small-scale wind systems. Weather 37, 295–306.CrossRefGoogle Scholar
Pedgley, D.E., Page, W.W., Mushi, A., Odiyo, P., Amisi, J., Dewhurst, C.F., Dunstan, W.R., Fishpool, L.D.C., Harvey, A.W., Megenasa, T. & Rose, D.J.W. (1989) Onset and spread of an African armyworm upsurge. Ecological Entomology 14, 311–333CrossRefGoogle Scholar
Persson, B. (1981) Population fluctuations of the African armyworm Spodoptera exempta (Wlk) (Lep Noctuidae) in outdoor cages in Kenya. Bulletin of Entomological Research 71, 289–297.Google Scholar
Riley, J.R., Reynolds, D.R. & Farmery, M.J. (1983) Observations of the flight behaviour of the armyworm moth, Spodoptera exempta at an emergence site using radar and infra-red optical techniques. Ecological Entomology 8, 395–418.CrossRefGoogle Scholar
Rose, D.J.W. (1975) Field development and quality changes in successive generations of Spodoptera exempta Wlk; the African armyworm. Journal of Applied Ecology 12, 727–739.Google Scholar
Rose, D.J.W. (1979) The significance of low-density populations of the African armyworm Spodoptera exempta (Wlk). Philosophical Transactions of the Royal Society, London B 287, 393–402.Google Scholar
Rose, D.J.W., Page, W.W., Dewhurst, C.F., Riley, J.R., Reynolds, D.R., Pedgley, D.E. & Tucker, M.R. (1985) Downwind migration of the African armyworm moth, Spodoptera exempta, studied by mark-and-capture and by radar. Ecological Entomology 10, 299–313.CrossRefGoogle Scholar
Rose, D.J.W., Dewhurst, C.F., Page, W.W. & Fishpool, L.D.C. (1987) The role of migration in the life system of the African armyworm Spodoptera exempta. Insect Science and Its Application 8, 561–569.Google Scholar
Tucker, M.R. (1984a) Possible sources of outbreaks of the armyworm, Spodoptera exempta (Walker) (Lepidoptera: Noctuidae) in East Africa at the beginning of the season. Bulletin of Entomological Research 75, 599–607.CrossRefGoogle Scholar
Tucker, M.R. (1984b) Forecasting the severity of armyworm seasons in East Africa from early season rainfall. Insect Science and Its Application 5, 51–55.Google Scholar
Tucker, M.R. (1993) Weather and the epidemiology of the African armyworm (Spodoptera exempta). NRI Bulletin No. 58, Natural Resources Institute, Chatham UK.Google Scholar
Tucker, M.R. & Pedgley, D.E. (1983) Rainfall and outbreaks of the African armyworm Spodoptera exempta (Walker) (Lepidoptera Noctuidae). Bulletin of Entomological Research 73, 195–199.Google Scholar
Tucker, M.R., Mwandoto, S. & Pedgley, D.E. (1982) Further evidence for windborne movement of armyworm moths, Spodoptera exempta, in East Africa. Ecological Entomology 7, 463–473.Google Scholar
Wilson, K. & Gatehouse, A.G. (1993) Seasonal and geographical variation in the migratory potential of outbreak populations of the African armyworm moth Spodoptera exempta. Journal of Animal Ecology 62, 169–181.Google Scholar
Woodrow, K.P., Gatehouse, A.G. & Davies, D.A. (1987) The effect of larval phase on flight performance of African armyworm moths Spodoptera exempta (Walker) (Lepidoptera Noctuidae). Bulletin of Entomological Research 77, 113–122.CrossRefGoogle Scholar