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Distribution, frequency of attack and seasonal incidence of the African armyworm Spodoptera exempta (Walk.) (Lep.: Noctuidae), with particular reference to Africa and southwestern Arabia

Distribution, frequency of attack and seasonal incidence of the African armyworm Spodoptera exempta (Walk.) (Lep.: Noctuidae), with particular reference to Africa and southwestern Arabia

Haggis, Margaret J. (1984) Distribution, frequency of attack and seasonal incidence of the African armyworm Spodoptera exempta (Walk.) (Lep.: Noctuidae), with particular reference to Africa and southwestern Arabia. Tropical Development and Research Institute (TDRI), London, UK. ISBN 0851351395

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Abstract

Distribution, frequency of attack and seasonal incidence of the African armyworm Spodoptera exempta (Walk.) (Lep.: Noctuidae), with particular reference to Africa and southwestern Arabia Spodoptera exempta (Walk.) is recorded very widely in Africa south of the Sahara and in adjacent parts of southwestern Arabia. It occurs intermittently through the oceanic countries of South East Asia and the Pacific as far east as Hawaii, but not in the Americas. This distribution is mapped in detail. The areas from which infestations have been reported and the frequency of attack have increased since 1970. This paper aims to help those concerned with monitoring and control of armyworm by making available the wider historical data needed for anticipating outbreaks. For the pan-African region, the monthly distribution and frequencies of incidence are presented as twelve maps showing the number of years in which infestations have been recorded in each degree-square of latitude and longitude during the period 1940-1982. In the areas to the north and south of about 4°N, the periods of attack are roughly complementary and correspond with the seasonal rains. Thus from October-November until May infestations spread progressively northwards from southern Tanzania to northern Ethiopia and Yemen, and at the same time southwards from Malawi and Zimbabwe to the south of Cape Province. From June until September infestations occur intermittently from Senegal to southwestern Arabia, but very rarely south of the equator. The northward and southward progressions of outbreaks can be attributed to the migration of the moths on the wind. The scarcity of reports from all parts of the region in September-October and the start of the next season in the area between southeastern Kenya and Zimbabwe lend support to the alternative theory that outbreaks may develop from populations that remain at low density, particularly within this area. Evidence from other disciplines supporting both theories is outlined. Sequencies of attack do not follow exactly the same pattern each season. To enable years with events analogous to the current one to be identified, the range of recorded variations is appended as a series of maps showing month by month the distribution of S. exempta infestations over the last 43 years. For each territory there is an index to the years and months when outbreaks were recorded, and a summary of the monthly frequencies of occurrence. The incidence and importance of S. exempta in each country is summarised.

Item Type: Book
Uncontrolled Keywords: Africa, Arabia, African armyworm, Spodoptera exempta, distribution, outbreak, monitoring
Faculty / Department / Research Group: Faculty of Engineering & Science > Natural Resources Institute
Related URLs:
Last Modified: 18 Oct 2016 09:13
Selected for GREAT 2016: None
Selected for GREAT 2017: None
Selected for GREAT 2018: None
URI: http://gala.gre.ac.uk/id/eprint/12588

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