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

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Abstract
Occurrences of outbreaks of the African armyworm, S. exempta, between Jan. and Dec. for 19 yr (1961-1979) and records on nightly moth catches from light trap stations located between southern Kenya and east-central Tanzania (1-8% S and 35-41% E) for 16 yr (1963-1978), were mapped, tabulated and analyzed on a standard weekly time-table, in order to compare events occurring between the off-season months of July-Nov. and the beginning of the outbreak seasons from Dec. or Jan. Circumstantial evidence from the above, coupled with analysis of climatological statistics for rainfall, temperature and windflow over the area and period, support the hypothesis that populations of S. exempta can survive between southern Kenya and east-central Tanzania during the off-season months, and contribute to the initial development of outbreak season in Tanzania or Kenya. Methods for monitoring and analyzing such developments for improving the efficiency of the armyworm forecasting service in East Africa are suggested.