A nutritionally complete pollen-replacing diet protects honey bee colonies during stressful commercial pollination: Requirement for isofucosterol

A steady supply of nutritionally adequate pollen from diverse flower
sources is crucial for honeybee colonies. However, climate instability,
large-scale agriculture, and the loss of flower-rich landscapes have made
this supply scarce and unpredictable, threatening both apiculture and
sustainable crop pollination. We developed a nutritionally
complete pollen-replacing diet that supports continuous brood production
from May to October in colonies without access to pollen. Omitting
isofucosterol, the third most abundant sterol in honeybees, causes
significant reductions in brood production and neuromuscular dysfunction
in adults, identifying isofucosterol as a critical micronutrient. In
contrast, omitting 24-methylene cholesterol, the most abundant honeybee
sterol, does not significantly affect brood production, and surprisingly,
bees remain viable without it. Colonies fed a commercial diet severely
declined in brood production after 36 days and died out. In a season-long
experiment in the commercial pollination of blueberry and sunflower
fields, a treatment group fed the complete diet overcame the detrimental
effects of nutritional stress, unlike colonies in "No Diet" and
"Commercial Diet" groups. This study suggests that
feeding a complete, pollen-replacing diet to nutritionally stressed
colonies can address the root causes of honeybees' growing
nutritional deficiencies, supporting their health and their vital
pollination services.