# Honey Bee Pollination of Camellia oleifera and Mitigation of Toxic Crop Nectar

## TL;DR

Honey bees can pollinate tea oil trees in winter, but their nectar is toxic; adding an enzyme helps bees survive and improves pollination.

## Contribution

A novel method using α-galactosidase to detoxify tea oil tree nectar for honey bees is proposed.

## Key findings

- Tea oil tree nectar is toxic to honey bee larvae but toxicity can be reduced with α-galactosidase.
- Honey bee pollination increases fruit set and seed yield, especially in warmer years.
- Administering α-galactosidase improves larval survival when exposed to toxic nectar.

## Abstract

Tea oil trees (Camellia oleifera) bloom in winter when wild pollinators are scarce. Managed honey bees could provide pollination services at this time; however, the nectar of tea oil trees is toxic to honey bees because they cannot digest its oligosaccharides, hindering sustainable pollination. This study aims to clarify the ecotoxicity of tea oil tree nectar on eastern honey bees (Apis cerana) and to propose a mitigation solution for its toxic effect. We found that tea oil tree nectar is toxic to honey bee larvae, but this toxicity can be alleviated by administrating α-galactosidase that can break down oligosaccharides in the digestive system. In addition, we observed that the effectiveness of pollination is affected by annual weather variations, suggesting that honey bee pollination provides greater benefits in favorable years with typically warmer temperatures. Our research offers a promising method for detoxifying this toxic nectar for honey bees, thereby enabling the sustainable pollination of tea oil trees by honey bees.

Tea oil tree (Camellia oleifera), a woody oil crop native to Southern China, relies on insect pollination for fruit and seed production. However, its nectar is toxic to honey bees (Apis spp.) due to their inability to digest the oligosaccharide present in the nectar. This toxicity raises concerns about the trade-off between the benefits of pollination and the risks posed by exposures to toxic nectar. We aimed to investigate whether tea oil tree yield is enhanced by honey bee pollination, while also examining the impact of nectar toxicity and exploring potential mitigation methods. We evaluated the fruit set, seed yield, and oil quality of the crop with or without eastern honey bee (A. cerana) pollination during 2019–2022. We also characterized nectar oligosaccharide compositions collected from both flowers and bee hives. We administered α-galactosidase (an enzyme to promote oligosaccharide digestion) onto bee larvae fed with crop nectar. We found that A. cerana could significantly enhance fruit set and seed yield. The administration of α-galactosidase could enhance larval survivorship challenged by nectar toxicity. The effectiveness of honey bee pollination can vary between years, with warmer temperatures significantly enhancing honey bee pollination benefits. The results suggest that a decision to use honey bees for pollinating tea oil trees should involve consideration of the impact of local weather conditions, as low temperatures may compromise pollination benefits while increasing risks posed by toxic nectar. The administration of digestive enzymes to honey bees shows potential for mitigating natural toxins in tea oil tree nectar.