The Foraging Behaviour of Honeybees (Apis mellifera L.) on Brussels Sprout (Brassica oleracea L.)

Abstract

Many crops needing insect pollination are grown where their natural pollinators do not occur. Honeybees (Apis mellifera L.) can often be used as effective substitutes but, because they are incompletely adapted to the flowers, they sometimes obtain nectar without pollinating them. For example, honeybees sometimes cannot reach the nectar of red clover (Trifolium pratense L.) and field bean (Viciafaba L.) through their narrow, deep corolla tubes and obtain it only through holes bitten by bumblebees (Bombus spp.) at the bases of the flowers. The structure of other flowers, e.g. bluebell (Scilla nonscripta Hoffm. and Link) and wild cabbage (Brassica oleracea L.), enables honeybees to obtain nectar by inserting their tongues between the bases of the perianth segments. Because this habit can diminish the pollinating efficiency of honeybees, we have studied how it is acquired by bees foraging on Brussels sprout (B. oleracea cv. gemmifera Zenk) flowers and how to prevent its acquisition. Difficulties in obtaining sufficient cross-pollination by honeybees between Brussels sprout cultivars used for F1 hybrid seed production have been reported by Dixon (1971) and Faulkner (1971), so investigations have also been made on the behaviour of bees visiting different cultivars of Brussels sprout with floral parts of different sizes, and their constancy to them.