ABSTRACT The common bean is an important crop in Eastern Africa for smallholder farmers, yet yields are often reduced due to pests, particularly Ophiomyia spencerella and Ophiomyia phaseoli . These species are partially sympatric and commonly known as the bean fly. Here, based on the similarity of their life history and developmental biology, field data was collected over 2 years to develop a generic degree‐day model for the population growth of bean fly larvae to optimise the timings for the application of management interventions. There was a good fit between the observed larval emergence in the field and that predicted by the model (average R 2 = 0.99, r = 0.96 and RMSE = 0.05). As early action is recommended for bean fly populations, the suggested ‘time to act’ occurs when the predicted bean fly larval population is still low yet when the predicted rate of larval population growth begins to maximise. This equated to approximately 218 degree‐days from planting. The model shows good potential for practical application in bean growing areas to optimise timings for the control of bean fly populations.
Finch et al. (2026) studied this question.