Abstract
Insect crop pests are a major threat to food security in sub-Saharan Africa. Configuration of semi-natural habitat within agricultural landscapes has the potential to enhance biological pest control, helping to maintain yields whilst minimising the negative effects of pesticide use. Fall armyworm (Spodoptera frugiperda, J. E. Smith) is an increasingly important pest of maize in sub-Saharan Africa, with reports of yield loss between 12 and 45%. We investigated the patterns of fall armyworm leaf damage in maize crops in Ghana, and used pitfall traps and dummy caterpillars to assess the spatial distribution of potential fall armyworm predators. Crop damage from fall armyworm at our study sites increased significantly with distance from the field edge, by up to 4% per m. We found evidence that Araneae activity, richness and diversity correspondingly decreased with distance from semi-natural habitat, although Hymenoptera richness and diversity increased. Our preliminary findings suggest that modifying field configuration to increase the proximity of maize to semi-natural habitat may reduce fall armyworm damage and increase natural enemy activity within crops. Further research is required to determine the level of fall armyworm suppression achievable through natural enemies, and how effectively this could safeguard yields.
Highlights
The human population of sub-Saharan Africa is expected to at least double by 2050, necessitating a corresponding increase in food availability (Ittersum et al, 2016; Cleland and Machiyama, 2017)
Using a combination of empirical observation and experimental dummy caterpillars in Ghanaian maize fields we examine the relationship between distance from semi-natural habitat and FAW-mediated crop damage, and the abundance, richness and diversity of its potential natural enemies
To assess how herbivory from FAW varied with distance from field margins in a rural smallholder agricultural setting, on 5 February 2019 we surveyed two fields of unharvested maize bordered by semi-natural habitat in Abutia Amegame (Volta Region of Ghana; 6.46°N, 0.32°E), referred to throughout as village maize (VM)
Summary
The human population of sub-Saharan Africa is expected to at least double by 2050, necessitating a corresponding increase in food availability (Ittersum et al, 2016; Cleland and Machiyama, 2017). Sustainable intensification to close the yield gap between current and maximum possible production could help improve food security in this region (Godfray et al, 2010; Godfray and Garnett, 2014). One barrier to improving food security is yield loss from invertebrate pest damage. Sustainable intensification includes an increased reliance on biological pest control (Garibaldi et al, 2017). As part of integrated pest management, this could increase yields while minimising the negative impacts of pesticide application such as environmental pollution and compromised human health (Bianchi et al, 2006; Kansiime et al, 2019; Tambo et al, 2020; Haggblade et al, 2021). The configuration of landscape natural capital stocks (e.g. semi-natural habitat surrounding cropland) can potentially be managed to increase the flow of biological pest control services, on smallholder farms (Steward et al, 2014)
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