BEHAVIORAL EFFECTS OF FOUR PESTICIDES ON BEES–THEIR POTENTIAL FOR SAFE CROP PRODUCTION, PROTECTING POLLINATORS AND ECOSYSTEM

Abstract

The toxicity of the neonicotinoid (Thiamethoxam, Imidacloprid and Thiacloprid) and Diamide (Chlorantroniprole) insecticides were tested orally and directly sprayed on honey bee species Apis mellifera, Apis dorsata, Apis florea, Apis cerana at 5 concentration levels (0.005/0.0025, 0.05/0.025, 0.5/0.25, 5/2.5,50/25ppm) in the laboratory. In the oral toxicity test, Thiamethoxam caused the highest mortality for all the bee species among the tested insecticides. At increasing dose levels, Thiamethoxam responsible for the mortality of A. florea (50, 85, 95, 100 and 100%), A. mellifera (60, 65, 85, 100 and100%), A. dorsata (100%) and A. cerana (65, 85, 75, 95 and 100%). On the other hand, Chlorantraniliprole showed the lowest mortality for A. florea (10, 20, 25, 35 and 50%), A. mellifera (15, 35, 40, 45 and 55%), A. dorsata (15, 30, 40, 45 and 50%) and A. cerana (15, 20, 25, 40 and 50%). In contact test, at increasing dose levels, Thiamethoxam demonstrated the highest mortality of A. mellifera (45, 55, 85 and 100%) with the exception of Imidacloprid (100%) at only 5/2.5ppm. Imidacloprid caused highest mortality (65%) of A. dorsata at only 0.05/0.025 ppm and Thiamethoxam (60,100, 100 and 100%)in other concentrations. Thiamethoxam also responsible for the highest mortality of A. cerana (70, 85, 100 and 100%) with the exception of Imidacloprid (70%) at only 0.05/ 0.025ppm. But Chlorantraniliprole showed the lowest mortality for A. florea (15, 20, 25, 45 and 55%), A. mellifera (0, 20, 20 and 35%) with the exception of Thiacloprid (20%) at 5/2.5ppm, A. dorsata (0, 20, 30, 30 and 35%) and A. cerana (25, 30, 35, 40 and 45%). The LC50 of Thiamethoxam (0.002ng/µL) and Imidacloprid (0.007ng/µL) were obviously the most harmful to honey bees among the tested insecticides, while Chlorantraniliprole showed the lowest harm to the foragers (265.79 ng/µL) and Thiacloprid (20.07ng/µL) were relatively medium to low toxic to bees at 48 h after the exposure. All the bee species were highly toxic to Thiamethoxam and Imidacloprid but low toxic to Thiacloprid and Cholantronoprole. It was found that there was a positive relationship between the mortality and concentration levels; when the concentration level increased, the mortality rate increased as well. However, there was a negative relationship between the mortality time and concentration levels; when the concentration levels increased, the mortality time decreased.