Development of a stage-structured process-based predator–prey model to analyse biological control of cotton aphid, Aphis gossypii, by the sevenspot ladybeetle, Coccinella septempunctata, in cotton

•We developed a stage-structured process-based predator-prey model.•The model was parameterized for cotton aphid and sevenspot ladybeetle in cotton.•The model was tested in field cages and in the open field.•Density dependent feedbacks and initial prey/predator ratio were key system drivers.•Initial prey/predator ratio is decisive for biological aphid control.