Bees and their contribution to the yield of robusta coffee and pumpkins in selected districts of central Uganda

Abstract

Bees play a vital role in enhancing the yields of flowering crops like Robusta coffee and pumpkins through pollination. This study investigated how cultivation practices influence bee diversity, abundance, and their contribution to the yields of Robusta coffee and pumpkins in the southern Kyoga basin district of Kayunga and central Lake Victoria Crescent districts of Luwero and Nakaseke. The research was conducted between July 2020 and April 2022. The study focused on Robusta coffee grown under shaded and open sun conditions, as well as pumpkin plots located at distances of ≤ 3 km and > 3 km from potential natural or semi-natural bee habitats. Bee diversity and abundance were assessed twice between December 2020 and October 2021 using pan trans and sweep nets across 100 m² plots established on each study site for the respective crops. Pollination exclusion treatments were undertaken to assess the impact of pollination on fruit set and yield. Statistical analysis using one-way ANOVA and logistic regression revealed that shaded Robusta coffee plots and pumpkin plots ≤ 3 km had significantly higher bee diversity, abundance, and crop yield. Hypotrigona sp. and Lasioglossum sp., were more prevalent in shaded conditions. Pumpkin plots ≤ 3 km exhibited higher fruit set, larger fruit mass, and greater seed counts than those > 3 km. In contrast, completely bagged flowers resulted in the complete absence of fruit production, underscoring the absolute dependence of pumpkins on insect pollination. The findings emphasize the critical role of agroforestry systems and the proximity of crops to pollinator habitats in enhancing pollination services and optimizing crop yields and hence the promotion of sustainable agriculture in Uganda.