Impact of Cannabis sativa (L.) inflorescences on the control of artificial Nosema (= Vairimorpha) ceranae infection in honey bees Apis mellifera ligustica (Spinola, 1806)

In light of the significant threat posed by declining honey bee populations to global ecosystems and agriculture, this study explores an innovative approach to face emerging pathogen threats. The present study investigates the efficacy of ground inflorescences from two Cannabis sativa genotypes as potential natural treatments for Nosema (= Vairimorpha) ceranae infection in honey bees. The plant genotypes analysed included a chemotype III selection, V1, with high cannabidiolic acid, and a chemotype I selection, V2, with a prevalence of tetrahydrocannabinolic acid. The inflorescences were incorporated into sugar candy at three concentrations w/w (1%, 2%, and 4%) and fed to bees that had been artificially infected with N. ceranae. Results showed significant differences in the survival of honey bees across treatments. All cannabis treatments reduced longevity compared to the control group. Notably, N. ceranae spore counts decreased in all treatment groups. Statistical analyses indicated that the control group experienced the highest increase in pathogen copies, while the fumagillin treatment maintained the lowest infection. Water and food consumption varied among treatment groups, with V1-2, V2-2, and V2-4 formulations leading to increased intake. The median lethal time for untreated bees was significantly longer than that for those treated with cannabis, while the survival of bees treated with V1-1 and V1-2 was longer than that of bees treated with fumagillin. These preliminary findings highlight the antimicrobial properties of cannabis inflorescences, highlighting cannabis as a potential natural intervention.