5.1.1. Bee densities in small field plots

Appropriate bee density measures vary according to plant growth habit, planting arrangement and conformation of flowering. Examples of density measures that may be used include:

  • Bees per m2 or larger area (especially for vine crops)
  • Bees per tree (tree fruits and nuts)
  • Bees per flower or larger number of flowers (berries, vine crops, cotton, sunflower)

Considerations when counting bees:

  • Make several observations through the duration of the flowering period
  • Subsample within a day, recording time of samples as local solar time
  • Sample during weather conditions that are favourable for foraging, i.e., temperature ≥15°C, wind <16 km/h, no rain (flowers dry) and preferably sunny
  • Also sample for pollinator diversity

Considerations in choosing sampling sites:

  • Use multiple sampling sites within a field
  • Choose representative sites that are at least 5 m from the field edge
  • Use >1 m of row in row crops
  • Use plots of >1 m2 in broadcast-seeded plots and non-row crops
  • Use individual branches of trees in orchards
  • Use individual flowers if large enough (e.g., sunflowers)

Considerations when measuring yield are as in sections 2 and 6.

Vaissière et al. (2011) give detailed suggestions about assessing pollination needs of different types of crops. They also provide useful data collection sheets for recording bee count and yield information for crop of different growth habits.