Uncertainties in the effectiveness of biological control of stem borers under different climate change scenarios in Eastern Africa

Climate change (CC) is expected to significantly affect biodiversity and ecosystem services. Adverse impacts from CC in the Global South are likely to be exacerbated by limited capacities to take adequate adaptation measures and existing developmental challenges. Insect pests today are already causing considerable yield losses in agricultural crop production in East Africa. Studies have shown that insects are strongly responding to CC by proliferation, shift in distribution, and by altering their phenology, which is why an impact on agriculture can be expected. Biological control (BC) has been proposed as an alternative measure to sustainably contain insect pests, but few studies predict its efficacy under future CC. Using the species maximum entropy modeling (Maxent) approach, we predict the current and future distribution of three important lepidopteran stem borer pests of maize in Eastern Africa, i.e., Busseola fusca (Fuller, 1901), Chilo partellus (Swinhoe, 1885), and Sesamia calamistis (Hampson, 1910), and two parasitoids that are currently used for BC, i.e., Cotesia flavipes (Cameron, 1891) and Cotesia sesamiae (Cameron, 1906) . Based on these potential distributions and data collected during household surveys with local farmers in Kenya and Tanzania, also future maize yield losses are predicted for a business-as-usual scenario and a sustainable development scenario. We found that BC of the stem borer pests by C. flavipes and C. sesamiae will be less effective under more severe CC resulting in a reduced ability to curb maize yield losses caused by the stem borers. These results highlight the need to adapt BC measures to future CC to maintain its potential for environmentally friendly pest management strategies. The findings of this research are thus of particular relevance to policymakers, extension officers, and farmers in the region and will aid the adaptation of smallholder agricultural practices to the impacts of CC.