Coffee trees intercropped with common beans: An opportunity to regulate the aphid Toxoptera aurantii (Boyer de Fonscolombe) (Hemiptera: Aphididae) in coffee agroecosystems

The coffee aphid Toxoptera aurantii (Boyer de Fonscolombe) (Hemiptera: Aphididae) causes direct feeding injuries and vectors the coffee ringspot virus (CoRSV) (Mononegavirales: Rhabdoviridae), which is more damaging to coffee plants. Coffee farmers have controlled this pest using synthetic pesticides. However, chemical control is ineffective and sometimes associated with resistance, environmental pollution, and pest resurgence, leading to the deterioration of agricultural ecosystem services. Therefore, there is a need to find more effective and safe biocontrol agents to keep this pest under the economic threshold. In that context, we installed six plots to compare the dynamics of aphid populations in coffee trees intercropped with common beans (Phaseolus vulgaris L., Fabales: Fabaceae) to coffee monoculture farming systems in open fields in the Southern Province of Rwanda. Results show a significant difference in infestations of coffee aphids. The population of aphids is higher in coffee monocultures than in intercropping systems. Our results also indicate that beneficial insects respond positively to the intercropping system with more species of natural enemies, mostly ladybird beetles (Coccinellidae), hoverflies (Syrphidae), and wasps (Vespidae) than in monocultures. No Hymenoptera were observed in coffee monoculture plots, indicating that common beans attract diverse natural enemies. Therefore, coffee trees intercropped with beans can help to maintain and diversify indigenous natural enemies in agroecosystems and regulate the aphid T. aurantii. We recommend future researchers use the Land Equivalent Ratio (LER) and compare these coffee farming systems to help people decide exactly what intercropping crops yield should be.