Honeybee gut microbiota plays a crucial role in maintaining their health and digestive function. Studies have confirmed that quercetin improves honeybee health by enhancing their pesticide tolerance and survival rates. This study aimed to examine the effects of quercetin on the bee gut microbiome by absolute quantification sequencing. We included 1800 bees from the experimental apiary and exposed them to 151.2, 75.6, and 37.8 mg/L of quercetin. Gut samples were collected on the 5th and 9th days, subjected to a polymerase chain reaction and 16S rRNA sequencing, and analyzed. After 5 days of quercetin treatment, the diversity of the honeybee gut microbiota was altered, and total bacterial copies and Lactobacillus abundance significantly decreased at high quercetin concentrations (151.2 and 75.6 mg/L). On day 9, the gut microbial community had recovered from the adverse effects, and Gilliamella abundance increased in response to 37.8 mg/L quercetin treatment. However, quercetin had no noticeable effects on survival rate, food consumption, and gut structure. Our study confirmed the effect of short-term quercetin intake on the gut microbiota of A. cerana, providing valuable insights into how phytochemicals alter the bee gut microbiome, and their repercussions on host physiology.

As the predominant native pollinator across Asia, Apis cerana is essential for the maintenance of biodiversity and agricultural productivity. The gut microbiota of honeybees plays a central role in host nutrition, detoxification, and immune function. p-Coumaric acid, a widespread phenolic acid enriched in pollen and nectar, has been reported to promote honeybee health by prolonging lifespan and increasing the expression of detoxification-related genes, hence improving tolerance to pesticides. Its influence on gut microbial communities, however, remains insufficiently characterized in A. cerana. This study evaluated the effects of dietary p-coumaric acid on survival, sucrose solution consumption, and gut microbiome composition in A. cerana workers using absolute quantification sequencing. Bees were provided sucrose solutions containing p-coumaric acid at concentrations of 41.0, 82.0, and 164.0 mg/L for durations of 5 and 10 days. The results indicated no effect on survival but revealed time-dependent changes in sucrose solution consumption. p-Coumaric acid exposure altered the abundance of non-core bacterial taxa, including Bombella and Apilactobacillus, whereas the core gut microbiota (Lactobacillus, Gilliamella, Snodgrassella, Apibacter, and Bifidobacterium) remained stable. These results suggest that p-coumaric acid modulates sucrose solution consumption and selectively influences non-core gut bacteria without disrupting survival or core microbiota stability, underscoring its role in regulating host–microbe interactions in honeybees.