Susceptibility of faba bean variety ‘Merkurʼ to broadbean seed beetle (Bruchus rufimanus) in Latvia

The broadbean seed beetle (Bruchus rufimanus) is a significant pest of faba bean (Vicia faba) both in Latvia and in many other parts of the world. The objective of this study was to check the susceptibility of the faba bean variety ‘Merkurʼ to the broadbean seed beetle in Latvia, comparing it with other popular varieties: ‘Boxerʼ and ‘Lauraʼ. The trials were conducted in 2021 and 2022 at the Research and Study Farm ‘Peterlaukiʼ in Jelgava County and at a commercial farm in Cēsis County. The larval infestation rate of seeds of different varieties, the survival rate of individuals (larvae, pupae, imagines) in the seeds, as well as the percentage of seeds damaged by the pest in the yield were compared. It was observed that ‘Merkurʼ seeds were significantly less infested than ‘Boxerʼ and ‘Lauraʼ seeds. However, the survival rate of larvae in the seeds of ‘Merkurʼ was similar to that in ‘Lauraʼ seeds and higher than in ‘Boxerʼ seeds. The highest proportion of seeds damaged by the pest was found in the ‘Merkurʼ and ‘Boxerʼ yields, varying between 5–75% between years and trial locations. Therefore, it was concluded that the variety ‘Merkurʼ, evaluated from a practical point of view, does not differ from the other two varieties. Without taking additional plant protection measures, the percentage of seeds damaged by the broadbean seed beetle can significantly exceed the maximum limit (3%) specified in the buyersʼ quality criteria.