A Study of the Plant/Insect Relationships and Pod-Setting in the Runner Bean (Phaseolus Multiflorus)

Pod-setting in runner bean crops depends on the building up and maintenance of a sufficiently large population of efficient insect pollinators, and this appears to be affected by the early spring weather.

Runner bean flowers were visited and could be pollinated both by bumblebees (Bombus spp.) and honeybees (Apis mellifera). Visits to the front of the flower for nectar or pollen resulted in pollination, but “nectar-robbing” via a hole bitten through the underside of the flower, caused little or no pollination. During periods of intense nectar-robbing activity, pollination efficiency varied widely and depended largely upon whether or not insects were also collecting pollen from the crop.

A technique was devised for measuring the daily insect pollinating efficiency in a crop, that is, the actual daily pod-set as a percentage of the potential daily pod- set. A simple visual method for assessing the current day’s pollinating activity in the field is described, and the efficiency thus indicated compares well with results obtained from experimental pollination efficiency measurements.