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

Odiyo, Peter Onyango

doi:10.1017/s1742758400000606

Cited by 11 publications

(27 citation statements)

References 7 publications

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“…Radar has been used to record not only the downwind departure from emergence site of both scattered moths and dense masses in the form of plumes (Riley e t al., 1981), but also an overflight of moths, moving downwind, between two radars 12-13km apart (J. R. Riley Some deductions are then made about sources of outbreaks and destinations of moths emerging from outbreak sites, on the assumption of downwind movement and using present knowledge o n the speed, timing and duration of flight. These maps complement those of Odiyo (1981) and clearly demonstrate the westward and later northward spread of outbreaks. Fig.…”

Section: Introductionsupporting

confidence: 59%

Further evidence for windborne movement of armyworm moths, Spodoptera exempta, in East Africa

Tucker

Mwandoto²,

Pedgley

1982

Ecological Entomology

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1. Comparison of dominant wind directions with seasonal redistribution of Spodopteru exempta caterpillar outbreaks in East Africa provides further circumstantial evidence to support the hypothesis of downwind migration by adult moths. 2. Calculated backward and forward tracks for sixty-nine nights during the 1973-74 and 1974-75 seasons, when there were sudden increases in numbers of moths caught at six light traps, illustrate the variability of downwind movement due to the effects of temporary atmospheric disturbances.3. Comparison of calculated tracks with known outbreaks before and after the nights of increased moth catch suggests that some outbreaks are derived from unreported sources, especially eariy in the season, and it.is therefore unwise to link new outbreaks only with known earlier ones.

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Section: Introductionsupporting

confidence: 59%

Further evidence for windborne movement of armyworm moths, Spodoptera exempta, in East Africa

Tucker

Mwandoto²,

Pedgley

1982

Ecological Entomology

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“…Average monthly rainfall totals of 40-70 mm, such as are found at the coast from July to November, favour host plant survival (Odiyo, 1981). Although extreme and persistent drought kills S. exempta (Persson, 1981), it is evident (tables 3, 5, 8) that persistently light or heavy rainfall is important for respectively enhancing or suppressing the survival of armyworm populations.…”

Section: Discussionmentioning

confidence: 99%

“…At the coast, however, the time from oviposition to eclosion averages 23 days, permitting 14 generations to complete development through the year (Persson, 1981). Ecological studies, including trajectory analyses, suggest that in both Kenya and Tanzania the moths which produce the first outbreaks of the season mostly originate in the coastal zone that can support persistent, low-density populations (Odiyo, 1981;Persson, 1981;Tucker, 1984b). Once initiated, the outbreaks provide major sources of moths which produce new outbreaks in turn.…”

Section: Introductionmentioning

confidence: 99%

Forecasting the severity of seasonal outbreaks of African armyworm, Spodoptera exempta (Lepidoptera: Noctuidae) in kenya from the previous year's rainfall

Haggis

1996

Bull. Entomol. Res.

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Rainfall records for 23 years at 21 selected stations in Kenya were summarized and compared with the numbers of outbreaks of armyworm Spodoptera exempta (Walker) reported in the following season. The numbers of outbreaks were found to be negatively correlated with the rainfall of the 6-8 months preceding the start of the season. Stations in south-eastern Kenya, including the coastal belt which harbours the most extensive off-season source populations of S. exempta, were identified as key stations for forecasting whether to anticipate local or countrywide armyworm outbreaks next season. A scheme is suggested that would enable a provisional forecast to be made as soon as the long rains (April-May) rainfall records were available, and confirmed or revised subsequently in the light of the June-October rainfall at stations in south-eastern Kenya.

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“…Greater detail for eastern Africa is provided by historical records of moth-trap catches and armyworm outbreaks held at DLCO-EA, Nairobi. A guide to the seasonal changes of distribution in East Africa has been produced by Odiyo (1984), with the positions of the first outbreaks of the season in Kenya and Tanzania described in Odiyo (1981). There is also a wealth of information in published papers describing the development of the armyworm forecast service (Betts et al 1970;Odiyo 1975Odiyo , 1977Odiyo , 1979Betts 1976).…”

Section: Seasonal Distributionmentioning

confidence: 99%

“…Odiyo (1981) presents summaries of the mean monthly totals of moth catches for the network of light traps in Kenya, Tanzania and Uganda. There is a 10000-fold increase in catches during a period of 2 months following the off-season in Kenya.…”

Section: Population Cyclesmentioning

confidence: 99%

The bionomics of the African armyworm Spodoptera exempta in relation to its status as a migrant pest

Rose

Dewhurst

Page

1995

Integr Pest Manag Rev

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A multidisciplinary study was undertaken on the bionomics of the African armyworm in eastern Africa as a basis for the development of control strategies for this important pest of cereal crops and pastures. Relevant findings from studies on seasonal distribution, migration, field infestations and population cycles are reviewed in relation to understanding the causes for the onset and spread of armyworm outbreaks. It is concluded that the onset of the first outbreaks of an armyworm epidemic is caused by oviposition at high density by moths concentrated by wind convergence at storm outflows. The sources of these moths seem to be low-density populations which survive from one season to the next at sites receiving unseasonable rainfall. Some areas in Tanzania and Kenya are particularly prone to early outbreaks which are potentially critical for the initiation of a subsequent spread of outbreaks downwind throughout eastern Africa. These areas have low and erratic rainfall, and are near the first rising land inland from the coast. Below average rainfall prior to the development of outbreaks increases the probability of their occurrence. Their subsequent spread is enhanced by storms downwind which concentrate moths in flight and by sunshine during caterpillar development. Persistent wet weather reduces the spread of outbreaks. This study demonstrates the importance and value of developing and implementing a long-term monitoring system over a large region, in this case in Africa, not only for the generation of data used by the forecasters for the prediction and location of possible outbreaks, but also for obtaining a clearer understanding of the epidemiology of a highly mobile pest.

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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

Cited by 11 publications

References 7 publications

Further evidence for windborne movement of armyworm moths, Spodoptera exempta, in East Africa

Further evidence for windborne movement of armyworm moths, Spodoptera exempta, in East Africa

Forecasting the severity of seasonal outbreaks of African armyworm, Spodoptera exempta (Lepidoptera: Noctuidae) in kenya from the previous year's rainfall

The bionomics of the African armyworm Spodoptera exempta in relation to its status as a migrant pest

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