Pg. 7-8 Pollination of Bengal Litchi During the 1992 Flowering Season at Politsi: First Report

Honeybee foraging activity in a litchi orchard was monitored by investigating returning foragers for nectar, water, pollen and bee-glue. At commencement of flowering 22 beehives were introduced into a 10 ha orchard. Both nectar and pollen were collected throughout the day from litchi florets, as well as during the entire flowering period. Water was collected mainly in the afternoon, on some days only. No bee-glue was collected.

In a second experiment in which fruit-set was studied, 400 panicles were marked on 20 trees and left open. A second set of 400 panicles was bagged with 1 mm’ gauze to exclude insects. A mean set of six fruits (range 0-35) per open-pollinated panicle was recorded, compared to two fruits per bagged panicle. The mean weight per fruit was 18 g per fruit for open panicles.

Summary:

• The study monitored honeybee foraging activity in a 10-hectare Bengal litchi orchard at Politsi during the 1992 flowering season.
• At the start of flowering, 22 beehives were introduced to enhance pollination and honey production.
• Honeybee foragers collected both nectar and pollen throughout the day and the flowering period; water collection mostly occurred in the afternoons, while no bee-glue (propolis) was collected.
• Fruit-set was studied by marking 400 panicles on 20 trees; half were left open for insect pollination and half were bagged to exclude insects.
• Open-pollinated panicles averaged six fruits each (range 0-35), while bagged panicles averaged two fruits each; indicating insect pollination increased fruit set by approximately 300%.
• The mean fruit weight was similar for open-pollinated (18 g) and bagged panicles (17 g), showing pollination did not affect fruit size.
• Litchi flowers exhibit different floret types (male, functionally female, imperfect hermaphrodites), with pollen viability varying cyclically.
• Litchi is self-compatible but requires active pollen transfer by insects for good fruit set.
• Honeybee nectar foraging was highest in the morning and declined during the day; pollen foraging peaked around noon and declined in the afternoon; water foraging increased later in the day.
• No distinct daily or seasonal patterns for foraging loads emerged, but unsuccessful foragers (those carrying no loads) increased toward the afternoon.
• The findings suggest insect pollination, primarily by honeybees, plays a significant role in successful litchi fruit set in the orchard studied.