Plant measurements
We estimated plant density by counting the number of plants within a 0.25 m2 quadrat randomly placed in each cage. When pods reached maturity (BBCH-89), on 10th of September, 20 plants (stem, leaves, pods and roots) were collected per cage. On each plant, we counted the number of pods, number of beans per pod, proportion of damaged beans (beans with B. rufimanus emergence holes), plant height and tap-root length. Pods were classified into three categories: mature, immature (small and green) and unfertilized (without beans inside). Roots were washed with water. Aboveground plant (stems and leaves) and root biomass and bean weight for each plant were dried at 65°C for 48 hours and subsequently weighed. Beans per pod was averaged per plant prior to statistical analyses, beans per plant was calculated by summing the number of beans across pods per plant and individual bean weight was calculated by dividing bean weight per plant with number of beans per plant. Yield in kg.ha-1 was calculated for each cage by multiplying average bean weight per plant with plant density.