HONEY-BEE (HYMENOPTERA, APIDAE) FORAGING BEHAVIOR AND RASPBERRY POLLINATION

A study on raspberry, Rubus idaeus L., pollination was undertaken in southern Quebec. Raspberry flowers were bagged before flowering began. Once the flowers bloomed, the bags were removed while data were collected. The number and length of honey bee (Apis mellifera L.) visits to these flowers were recorded. Their effect on pollination was quantified using the weight and number of drupelets on the resulting berries. The weight of berries and number of drupelets increased with the number and length of visits. The product harvested by honey bees, either nectar or pollen and nectar, was determined by observing foraging bee behavior. The cumulated visiting time to a given flower was most effective when foraging involved the collection of pollen and nectar rather than nectar only. Once this cumulated time adds up to about 150 s, pollination reaches a maximum. Five or six honey bee visits per flower are sufficient to attain adequate pollination and raspberry development.