Assessment of pollinator diversity and pollination services in mustard agroecosystems

Abstract:

While mustard (Brassica juncea) depends heavily on insect pollination for optimal seed set, the composition and service value of pollinator communities in Japanese mustard fields remain poorly documented. This research assessed pollinator diversity and pollination services across three mustard fields near Tsukuba, Ibaraki, Japan, during the 2022-2023 flowering season. Visual census at 10-minute intervals identified six pollinator groups; Apis cerana was the dominant visitor (38.2% of all visits), followed by Apis mellifera (24.7%). Shannon diversity index averaged 1.43 across sites. Cage exclusion experiments showed that open-pollinated plots yielded 1.62 t ha⁻¹, 47.3% higher than insect-excluded plots (1.10 t ha⁻¹). Pollinator visit frequency was strongly correlated with seed yield per plant (r = 0.84, p<0.01). The estimated economic value of pollination services was ¥284,000 ha⁻¹ per season. These findings highlight the importance of maintaining pollinator-friendly habitats adjacent to mustard fields.