Inadequate pollination is a major constraint to crop yield. Momordica charantia L. is a fruit crop of
economic interest in Kenya. Pollination ecology, pollinator diversity and their behaviour were studied in
Western Kenya. Pollination treatments included insect exclusion, open pollination (unrestricted insect
visits), hand cross-pollination and pollen augmentation. Yield components from treatments were
compared to identify the pollination requirements of this crop. Flowering started 45 days after
germination with the staminate flowers appearing first followed by rewardless pistillate flowers. The
ratio of pistillate to staminate flowers was 1: 13. Pollinator species included honey bees (Apis mellifera),
Plebeina hildebrandti, Lasioglossum sp. and carpenter bees (Xylocopa spp). Fruit set and yield were
pollen limited as all bagged flowers were aborted. Fruit set under natural pollination was very low and
this revealed the degree of pollen limitation in M. charantia. Low fruit set was consistent with
observation of high discrimination against pistillate flowers amongst potential pollinators. Smaller bees
belonging to families Apidae (Plebeina hildebrandti) and Halictidae (Lasioglossum sp.) were the most
important pollinators. These observations highlight the importance of (1) a diverse fauna of wild bees
and (2) the potential of meliponiculutre in the increasing the yield of M. charantia in Kenya.
Key words: Plebeina hildebrandti, Lasioglossum, discrimination, deceit pollination, yield.