The behaviour of honey bees (Apis mellifera) visiting avocado (Persea americana) flowers and theircontribution to its pollination
Gad Ish-Am; Dan Eisikowitch
Observations of honey bee (Apis mellifera) foraging behaviour on five cultivars of avocado (Persea americana) were carried out in 1982-1984 and 1990-1992 in Galilee, Israel. Examination of the morphology of avocado flowers showed that the pistillate and staminate flower stages have similar structures. Bees collecting nectar, or nectar and pollen, visited both pistillate and staminate flowers, and due to the flower structure they were forced to touch both pistil and anthers. Only limited sites on a bee's body contacted the anthers, and these 'collection sites' also contacted the stigma, which occupied the same position as the anthers of the inner stamens. Most avocado pollen grains on bees visiting staminate flowers were clumped at the 'collection sites' and constituted the main pollen available for pollination. Some pollen grains randomly distributed over the entire bodies of bees visiting either pistillate or staminate flowers could have been acquired inside the hive, and did not play an important role in pollination. The observations suggest that pollination within a cultivar is accomplished during the overlapping phase of its pistillate and staminate flowering, during which bees collecting nectar and pollen move freely among neighbouring staminate and pistillate flowers. Pollination between cultivars of opposite flowering type is carried out by bees moving between them throughout the overlapping period of pistillate flowering of one cultivar and staminate flowering of the other. Bees which collect only pollen usually do not visit pistillate flowers and do not contribute to pollination.