Abstract
Busseola fusca (Fuller) (Lepidoptera: Noctuidae) is a destructive pest of maize throughout the African continent. Bt maize is an effective control measure for this pest, however, selection pressure for resistance evolution is high. This necessitates the implementation of insect resistance management (IRM) strategies such as the high-dose/refuge strategy. This IRM strategy relies on the validity of several assumptions about the behaviour of pests during insect-hostplant interactions. In this study, the migration behaviour of B. fusca larvae was evaluated in a semi-field (greenhouse) and field setting. The effect of factors such as different Cry proteins, plant growth stage at infestation, and plant density on the rate and distance of larval migration were investigated over four and five week periods. Migration of the larvae were recorded by using both a leaf feeding damage rating scale and destructive sampling at the end of the trials. Results indicated that B. fusca larval migration success was significantly affected by plant growth stage and plant density—while limited larval migration was recorded in plots inoculated with larvae at a late growth stage (V10), higher plant density facilitated increased interplant migration. The results also suggest that B. fusca larvae do not migrate extensively (rarely further than two plants from the natal plant) and that larval mortality is high. Implications for IRM strategies are discussed.
Highlights
The African stem borer, Busseola fusca (Fuller) (Lepidoptera: Noctuidae) is a destructive pest of maize and sorghum throughout sub-Saharan African [1,2]
This study allows for the better understanding of B. fusca larval migration behaviour on maize
This will inform decisions about possible resistance management strategies to implement for this pest in Africa
Summary
The African stem borer, Busseola fusca (Fuller) (Lepidoptera: Noctuidae) is a destructive pest of maize and sorghum throughout sub-Saharan African [1,2]. The predominant threat to the sustainability of Bt maize technology is the evolution of resistance by pest populations [7,8,9,10]. The widespread use and efficacy of Bt crops result in high and continuous selection pressure for resistance evolution throughout the growing season [11,12]. During the first decade of commercially available Bt crops (1996–2005), only three cases of field-evolved insect resistance to Cry proteins were reported. Busseola fusca was one of the first maize pests to exhibit field-evolved resistance to Cry 1Ab maize and did so within a mere eight years
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