| In nature bees are the most important pollinators.They not only pollinate many plants, but also for their own survival and reproduction of food — honey and pollen. Bee pollination benefits generated higher than their value of 5 to 12 times. Bee has economic, ecological and social benefits for agricultural production and maintenance of biological diversity of ecosystems have important and far-reaching significance.There have been many research reports on the impact of pesticides on bees at home and abroad. On one hand, the research focused on in the laboratory, half field and field under the condition of the pesticide and insect dose effect relationship; On the other hand, focus on the growth and development of pesticides to bees, behavior and physiological aspects of sublethal effects and then gradually become the focus of research.With the widespread application of neonicotinoid pesticides, such pesticides for pollinating insects, especially the influence to bees has takes people more and more attention.For a comprehensive evaluation of such pesticides on bee toxicity and risk, the paper takes seven kinds of neonicotinoids commonly used in the production and evaluate the toxicity of different kinds of such pesticides to bees and risk. Selected representative species-imidacloprid, studied the different formulations imidacloprid and bioassay methods method for the influence of the acute toxicity to bees. Sublethal doses of imidacloprid treatment bee 3rd instars, study the acute toxicity effect and determine the sublethal doses. Obtained under the condition of sublethal, imidacloprid for bee larvae, pupa weight rate, average rate of pupa weight, feather and the influence of the index such as the success rate of development. And studied the sublethal doses of imidacloprid on bee detoxification enzymes in the body and the dose effect of target enzyme, so as to the proper use of the new neonicotinoid insecticides and provide a theoretical basis for the bees to protect. The research results are as follows:1. The largest market share in the production of three varieties: imidacloprid, thiamethoxam and clothianidin have higher risk of toxicity to bees. Acetamiprid, thiacloprid, although market share is relatively small, but it has the advantage of low toxicity to bees acute toxicity and low risk. Nitenpyram, is less than the risk of thiacloprid, acetamiprid high, but much lower than imidacloprid, thiamethoxam and clothianidin, has good market prospects.2. Different formulations of imidacloprid mellifera acute toxicity. Acute oral LC50(48 h) between 3.552~15.928 mg ai/L, the overall exhibit ME> EC> SL> SC> WP> TC>WDG. Toxicity with improved dispersion of the dosage form is raised.Acute contact LD50(48 h) values ranged from 0.101 ~ 0.250 ai μg/bee. Acute toxicity test results between different dosage forms.3. 97% imidacloprid as test subjects, using micro-drip method to obtain contact LD50(48h) =0.101 μg ai/bee, a small beaker law oral LC50(48h) = 12.599 mg ai/L, by feeding tube method oral LD50(48h)= 0.0289 μg ai/bee.4. Clear the acute toxicity of imidacloprid on bee larvae LC50=8.193 mg/100 g diet. The sublethal doses are: LC5=1.175 mg/100 g diet,LC10 = 1.804 mg/100 g diet, LC20 = 3.303 mg/100 g diet.5. With sublethal concentrations continue to increase, the average mortality rate of larvae increased average larval weight, pupation rate, average pupal weight, growth rate and success rate of emergence showing decreasing trend.6.CarE AchE GSTs were involved in the degradation of imidacloprid on bee larvae, along with the change of dose showed obvious dose effect. For larval development of pupa, defecate dose effect is not obvious, the possible reason is that imidacloprid in bees all metabolites in the body has a half-life of 25 h, imidacloprid and its metabolites by defecate eduction body outside, detoxification enzyme activity returns to normal levels. |
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