Protective role of plant-based pollen substitute diets against <i>Nosema</i> spores in <i>Apis mellifera</i> colonies

Nosema sp. causes a significant threat to honeybee populations, making it crucial to find effective mitigation strategies. The present study examines the impact of plant-based pollen substitute diets on Nosema spore infection in Apis mellifera L. colonies. The study explores the potential of phytochemicals, which have antimicrobial properties, as natural treatments to reduce Nosema infection. Seven experimental groups (Diet-2 to Diet-8 along with Diet-1 (control) of colonies were fed with different pollen substitute diets containing medicinal plant leaves such as coriander (Coriandrum sativum), moringa (Moringa oleifera), tulsi (Ocimum sanctum) and lemongrass (Cymbopogon citratus); fruit powders of amla (Embilica officinalis), guava (Psidium guava) and mixed diet containing equal quantities of all plant leaves and fruit powders, along with common ingredients like defatted soya flour, skimmed milk powder, brewer’s yeast, turmeric, vitamins and sugar syrup. The Diet-2 to Diet-8 were compared to a control group of colonies (Diet-1), which was only fed with sugar syrup. Nosema spores were counted in samples of 40 worker bees from experimental and control groups of colonies before feeding and at intervals of 8, 16, 24 and 32 days using an Improved Neubauer hemocytometer. Results showed that Diet-8 has significantly reduced the number of Nosema spores (50,000±28867.5 spores/bee) compared to the control group of colonies (5,50,000±28867.5 spores/bee). Diet-8 was more effective than other diets, suggesting that plant-based pollen substitute diets can help effectively manage Nosema infections and maintain healthy and disease-free honeybee colonies throughout the year.