Effects of stingless bee propolis on Nosema ceranae infected Asian honey bees, Apis cerana

Since Nosema ceranae causes mortality in honey bee populations in both managed apiaries and in the wild, many chemical compounds have been screened and tested for their abilities to suppress populations of N. ceranae. However, the use of synthetic substances has resulted in residues in colonies and honey bee products. The development of new methods for the control of nosema disease is therefore much needed by beekeepers and bee scientists. We evaluated the effects of propolis from the stingless bee Trigona apicalis on N. ceranae-infected Asian honey bees, Apis cerana. One-day-old N. ceranae free worker bees were individually inoculated with 2 μl of 50% sucrose solution containing 80,000 N. ceranae spores per bee and then fed with 50 and 70% (v/v) propolis extract in water. All propolis-treated bees had significantly higher survival rates than untreated bees (F5 = 92.6, p < 0.0001). Bees treated with the highest propolis concentration (70%) had the lowest infection ratio of cells, while the significantly highest spore count in a single bee was found in control bees (F5 = 390.3, p < 0001, F5 = 309.0, p < 0.001). These results suggest that the propolis may have toxic effects on N. ceranae spores, and could have potential use in disease management.