Nosemosis is one of the most common protozoan diseases of adult bees (Apis mellifera). Nosemosis is caused by two species of microsporidia; Nosema apis and Nosema ceranae. Nosema ceranae is potentially more dangerous because it has the ability to infect multiple cell types, and it is now the predominant microsporidian species in A. mellifera. In this study, we identified two anti-nosemosis plants, Aster scaber and Artemisia dubia, which reduced the spore development of N. ceranae in spore-infected cells. The most important aspect of our results was that our treatment was effective at non-toxic concentrations. Anti-nosemosis activities of both plants were revealed in honey bee experiments. Specifically, a mixed extract of both A. scaber and A. dubia showed stronger activity than treatment with each single extract alone. Although the mechanisms of action of A. scaber and A. dubia against N. ceranae are still unclear, our results suggest new medicaments and therapeutic methods to control N. ceranae infection.