Defoliation reduces photosynthetic area, negatively effecting overall plant vitality, which at the end, severely impacts seed quality and production. The economic importance of the loss in winter wheat (Triticum aestivum L.) due to larvae of the cereal leaf beetle (Oulema melanopus, CLB) generated studies investigating the significance of the flag leaf. Simultaneously, the role of other leaves remains rather undiscovered. We simulated herbivory caused by CLB larvae in a two-year study between 2017 and 2018. We removed different amounts of leaf material from two winter wheat cultivars, either from the flag leaves only, or from all leaves. The impact of artificial defoliation was measured in grain production per ear, and related to natural CLB larval herbivory. Removing all leaves simulated CLB larval herbivory more closely than the artificial defoliation of flag leaves only. Our results suggest that the relative importance of flag leaves in seed production may be lower than previously assumed. Further studies involving various cultivars are invited to enhance the knowledge on the significance of the damage done by CLB larvae.