First insights on barley as banker plant for Rhopalosiphum maidis to enhance Diaeretiella rapae in white cabbage

Banker plants are a common tool in integrated pest management for greenhouse crops, but limited research has been conducted on their use in open-field vegetable production. Therefore, we aimed to evaluate the potential of barley banker plants with alternative aphid hosts (Rhopalosiphum maidis Linnaeus) for promoting aphid parasitism in field-grown white cabbage in central Germany. In 2022, we compared control plots with three treatments involving barley sown between crop rows: barley alone, barley infested with R. maidis, and barley infested with R. maidis parasitised by Diaeretiella rapae (M'Intosh). In 2023, only barley infested with R. maidis was compared to the control. All barley treatments significantly reduced aphid numbers but did not affect parasitism rates in cabbage. However, the development of D. rapae on R. maidis was observed in the field. Due to study limitations, the system should be re-evaluated under controlled conditions in field cages and at larger scales.