First report of invasive Fall armyworm and African armyworm sharing the same maize plants in the field: implications for intra-guild competition

Abstract

Abstract Both the native African armyworm (Spodoptera exempta Walker), AAW, and the invasive Fall armyworm (Spodoptera frugiperda J.E. Smith), FAW, attack maize in Africa. The invasion of FAW in Africa has created a scenario where these two Spodoptera species might co-occur and interact with each other. This could have implications for pest management, including insecticide resistance management, biological control and the effectiveness of management practices. Given the much more aggressive nature of FAW in comparison to AAW, we predicted that where the two species co-occur, FAW would dominate the intra-guild interaction. Our study includes field observations of armyworms on both Cynodon grasses and maize, including the systematic sampling of smallholder maize farms in Arusha, Tanzania. We found that FAW larvae and AAW larvae can occur in the same field and even on the same plant and leaf simultaneously however, statistically, their joint distributions are consistent with a non-competitive association.