Effects of diets containing different concentrations of pollen and pollen substitutes on physiology, Nosema burden, and virus titers in the honey bee (Apis mellifera L.)

Authors: Watkins De Jong, Emily; DeGrandi-Hoffman, Gloria; Chen, Yanping - Judy; Graham, Richard; Ziolkowski, Nicholas

Submitted to: Apidologie
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/2/2019
Publication Date: 12/2/2019
Citation: Watkins de Jong, E.E., Hoffman, G.D., Chen, Y., Graham, R.H., Ziolkowski, N.F. 2019. Effects of diets containing different concentrations of pollen and pollen substitutes on physiology, Nosema burden, and virus titers in the honey bee (Apis mellifera L.). Apidologie. 50:845-858. https://doi.org/10.1007/s13592-019-00695-8.
DOI: https://doi.org/10.1007/s13592-019-00695-8

Interpretive Summary: Honey bees (Apis mellifera) are subjected to a variety of stressors, including parasites, pathogens, and pesticides that negatively impact colony health. Colonies are frequently fed pollen substitutes by beekeepers in an attempt to mitigate these stressors and to rapidly grow colonies in preparation for pollination services. However, recent publications have suggested that substitutes may not be providing adequate nutrition to support adequate immune and metabolic function. The association between nutrition and immunity is well established. If bees are not receiving adequate nutrition, their capacity to carry our necessary functions is diminished. This project explored the negative impacts of feeding substitute diets reported in previous studies and investigated the potential that the addition of a small amount of pollen into pollen substitute diets may help to mitigate these negative effects. We found that pollen substitutes were less digestible to honeybees and increased the prevalence of gut parasites and virus burden over those fed pure pollen. The addition of 10% pure pollen in the substitutes improved digestibility, parasite burden, and virus titers to levels compatible with feeding pollen. These results benefit beekeepers and the agricultural pollination industry by providing insight into a new diet (pollen and pollen substitute mix) that may help honeybees to better deal with stresses encountered throughout the year. Improving honeybee nutrition can help to increase the number of colonies available for pollination services, valued at $20 billion in annual agricultural production in the United States, and in turn benefit the agricultural yield of honeybee pollination-dependent crops.

Technical Abstract: Colonies of Apis mellifera provided with natural forage show decreased pathogen loads and increased overwintering success when compared with colonies provisioned with supplemental protein diets. Despite the potential benefits of a pollen-based diet, protein supplements are commonly used in colonies throughout the spring and increasingly through the fall and winter as the cost of pollen is greater than that of supplements and concerns exist over the potential for pollen to vector viruses to bee colonies. In this study, we compare virus burden in bees fed on pure pollen diets, purely supplemental protein diets, and diets containing 90% supplement and 10% pollen to examine whether the inclusion of small amounts of pollen mitigates the negative impacts of consuming protein supplements seen in preceding studies.