The honey bee (Apis mellifera) faces a significant threat from Varroa destructor, causing the losses of millions of colonies worldwide. While synthetic acaricides are widely used to control Varroa infestations, excessive application has led to resistant strains and poses side effects on the host. Consequently, there is an urgent need for a new acaricide that is both effective and affordable, yet safe to use on bees. One potential source of these acaricides is essential oils (EOs) and their constituents. This study evaluated the acaricidal properties of four essential oils (Eucalyptus globulus, Rosemary officinalis, Trachyspermum ammi (Ethiopian and Indian varieties), their constituents and mixture of constituents against V. destructor through the complete exposure method. Our finding showed that a 1:1 mixture of thymol and carvacrol (4 h-LC₅₀ = 42 μg/mL), thymol (4 h-LC₅₀ = 71 μg/mL), and T. ammi oil (4 h-LC₅₀ = 81–98 μg/mL) were the most toxic test samples against V. destructor. Honey bee behavior and selectivity were also assessed with one additional EO Thymus schimperi, indicating that T. schimperi, T. ammi, and their components were selective and did not affect the learning and memory of bees. In conclusion, the thymol and carvacrol (1:1) mixture was shown to be a promising replacement for synthetic acaricides, being three times more toxic than a commercial acaricide, fluvalinate (4 h-LC₅₀ = 143 μg/mL).

Bee pollination plays important roles in increasing the yield, weight, and quality of strawberries grown in greenhouses. Use of pesticides is often included in the pest management strategy to control insects, fungi and weeds. However, these pesticides can negatively affect bees, compromising greenhouse pollination programs. In this study, we investigate the effect of rosmarinic acid (RA) feeding on the longevity of honey bees after oral and contact exposure of bees to some selected 14 different pesticides and G-3KM (commercial product) was used as a positive control. Among the 14 pesticides tested, six were found to be highly toxic to honey bee workers as indicated by their 48h-LD50 (㎍/bee) values obtained from oral and spray bioassays; thiamethoxam (0.0002/0.0011), dinotefuran (0.005/0.018), emamectin benzoate (0.002/0.0002), spinetoram (0.018/0.001), sulfoxaflor (0.04/0.01), and cyantraniliprole (0.1/0.03), respectively. It was interesting to note that RA and G-3KM-supplemented feeding reduced honey bees mortality by 20-30% after they were exposed to high concentrations of the 6 highly toxic pesticides. The results indicate that RA could be used effectively in reducing honey bee mortality caused by pesticides.