Risk assessment of synthetic insecticides and botanicals to Western honey bee, Apis mellifera (Hymenoptera: Apidae)
摘要
Apis mellifera L. (Hymenoptera: Apidae) is well known for its multiple services to the ecosystem. There is a tremendous increase in domestication of this bee in Pakistan. However, the rate of colony collapse has also increased due to different factors. Insecticides cause drastic changes in behavior of colony members ultimately affecting colony health. In the current study, effect of commonly used insecticides/mixtures (abamectin + thiamethoxam, thiamethoxam + chlorantraniliprole, flonicamid, and imidacloprid) along with two botanicals (bitter apple extract and neem leaf extract) was studied against adults and larvae of worker caste of A. mellifera. Different concentrations of insecticides and botanicals were prepared and mixed in diet, and the bees were allowed to feed on that diet. The results indicated that the most toxic insecticide against the adult foraging bees was the mixture of thiamethoxam + chlorantraniliprole with the lowest LC50 values of 0.138 and 0.041 mg L−1 after 12 h and 24 h, respectively. All the treated individuals were dead after 24 h. The lowest toxic chemical was neem extract with the highest LC50 values of 72099.01 and 3664.23 mg L−1 after 12 and 24 h, respectively. Comparable results were obtained for A. mellifera larvae, with the LC₅₀ value for the thiamethoxam + chlorantraniliprole mixture significantly lower (0.003 mg L⁻¹) after 24 h of exposure. In contrast, the LC₅₀ value for neem leaf extract was substantially high (2213.18 mg L⁻¹) over the same period. It is concluded that the insecticide mixtures like thiamethoxam + chlorantraniliprole and abamectin + thiamethoxam are comparatively more toxic to bees. Hence, bee hives should be protected when such insecticides are included in the pest control program.