Managing orchard groundcover to reduce pollinator foraging post-bloom

Agricultural insecticides are believed to play a role in global pollinator decline. In mass-flowering orchard crops, recommendations to reduce exposure of pollinators to insecticides include spraying at periods when bees aren't foraging, such as dusk and dawn and outside of crop flowering times. However, the presence of flowering weeds within orchards mean pollinators may still be found foraging throughout the growing season, increasing the likelihood that exposure will still occur. We hypothesized that removing these weeds within orchard groundcover may reduce pollinator foraging post-bloom and thus reduce exposure of this group to pesticides. We tested this hypothesis by using herbicide to remove flowering broadleaf weeds in the sod middles ('groundcover') between rows of a nectarine orchard in New Jersey, USA, and assessing the effect on pollinator visitation via three different methods.

Significantly lower abundance, richness, diversity, and evenness of pollinators were found in plots where herbicide treatment had removed the majority of flowering weeds, compared to untreated plots. This was the case for bees, and for pollinators overall, and was reflected in both visual observations and active sampling through sweep netting. Passive sampling with blue vane traps failed to detect a difference between treatments.

Groundcover management in orchards is often employed as part of integrated pest management programs to remove alternative host plants of insect pests. The findings of this study show that it is also effective in reducing post-bloom pollinator foraging in orchards, thus potentially preventing exposure of these beneficial organisms to harmful insecticides. © 2021 Society of Chemical Industry.