The Impact of Reishi (Ganoderma lucidum) Supplementation on Managed Honey Bee (Apis mellifera) Survival and Colony Performance

Honey bee colony health is increasingly threatened by multiple stressors, resulting in unsustainable annual mortality rates. Proper nutrition supports colony resilience, but most supplementation strategies are hard to apply at commercial scale. This study is the first commercial-scale evaluation of Reishi (Ganoderma lucidum) extract supplementation, following 326 managed honey bee colonies (108 control, 218 supplemented) across 44 apiary sites over the period 2022–2026. Within each site, colonies were randomly assigned to receive Reishi extract by a dripping method or a syrup-only control. Colony and queen longevity, population dynamics, and Varroa destructor management was modelled using Kaplan–Meier survival curves, Bayesian Cox proportional hazards models, and a discrete Bayesian network. Supplemented colonies survived a mean of 367 days, compared with 247 days for controls. The 95% credible intervals for the Bayesian CoxPH did not overlap between groups for either colony or queen survival. Querying the trained network showed an average mortality rate of 8% in supplemented colonies versus 14% in controls. That gap widened under Varroa pressure: a 13-percentage-point reduction (7% vs. 20%) when mite loads were rising, and a 23-point reduction (2% vs. 25%) in colonies with stable population size and increasing Varroa drop rates. Linear mixed-effects models on three-month colony-attribute percent changes matched these patterns, with supplementation linked to significant increases in frames of bees (p = 0.004) and frames of brood (p < 0.001). Mutual-information analysis of the network showed colony survival and frames of brood as the attributes most strongly tied to supplementation. These findings suggest that Reishi supplementation is a scalable approach to supporting colony robustness in commercial apiaries.