Honey Bee Pollination Requirements for Triploid Watermelon

Honey bees ( Apis mellifera L.) are important pollinators of triploid watermelon [ Citrullus lanatus (Thunb.) Matsum & Nakai]. Pistillate (or female) watermelon flowers require multiple honey bee or other wild bee visitations after visiting staminate (or male) flowers for fruit set, and pollination is even more of a concern in triploid watermelon production since staminate flowers contain mostly nonviable pollen. Six honey bee visitation treatments—1) no visitation control, 2) two visits, 3) four visits, 4) eight visits, 5) 16 visits, and 6) open-pollinated control—were evaluated to determine the effectiveness of honey bee pollination on `Millionaire' triploid watermelon fruit set, yield, and quality utilizing `Crimson Sweet' at a 33% pollenizer frequency. `Millionaire' quality characters (hollow heart disorder or percent soluble solids) did not differ ( P > 0.05) between honey bee pollination treatments. The open-pollinated control provided the highest fruit set rate (80%) and the greatest triploid watermelon numbers and weights per plot compared to all other honey bee visitation treatments. Fruit set, and fruit numbers and weights per plot increased linearly as number of honey bee visits to pistillate flowers increased from 0 (no visit control) to the open-pollinated control (about 24 visits). This study indicated that between 16 and 24 honey bee visits are required to achieve maximum triploid watermelon fruit set and yields at a 33% pollenizer frequency, which is twice the number of honey bee visits required by seeded watermelons to achieve similar results. This is probably due to many honey bees visiting staminate triploid watermelon flowers (that are in close proximity) before visiting pistillate flowers thus providing mostly nonviable pollen that is useless for fruit set and development. Therefore, more honey bee visits to pistillate triploid watermelon flowers would be required to achieve maximum fruit set and subsequent development compared to seeded watermelons.