| Bradysia odoriphaga(Diptera: Sciaridae) is one of the most important pest in Chinese chive production. With the enlargement of the protective cultivated area of Chinese chive, the occurance and damage of B. odoriphaga becomes more and more serious and cause the heavy loss of the quality and yield of it. Due to the invisibility and alternation of generations of B. odoriphaga, it is difficult to be prevented. Many factors treat the food safety of Chinese chive, such as, high-toxic pesticides, overdose and unscientific pesticide application technology. In order to evaluate the application potential of chlorfenapyr against B. odoriphaga, the toxic effect, sublethal effect of chlorfenapyr to B. odoriphaga were determined in terms of population development, insec physiological and biochemical proterty. Combining the degradation dynamics of chlorfenapyr in the field of Chinese chive, influence on the growth of Chinese chive and control efficacy of B. odoriphaga, the present paper explored the field application techniques of chlorfenapyr against B. odoriphaga. The results were summarized as follow:1. The field population of B. odoriphaga were collected from seven different planting regions in Shandong province, such as, Weifang, Taian, Liaocheng, Linyi, Jinan, Dezhou. The toxicity of the lab and field populations were measured by stomach and contact joint toxicity method. The results showed that all of the populations showd different sensitivity to phoxin significantly. However, they were sensitive to chlorfenapyr, the LC50 were 9.88, 10.70, 10.88, 10.55, 8.73, 10.09, 10.54, 9.82 mg/L respectively.2. The toxicity of chlorfenapyr to each stage of B. odoriphaga were determined by dripping ration liquid method, stomach and contact joint toxicity method and residual film method. The results indicated that chlorfenapyr showed high toxicity to eggs, larvae, pupae and adults of B. odoriphaga. Compared the toxicity of first, second and fourth instar of the larvae of B. odoriphaga, it illustrated that there is no significant difference from the stages and the LC50 were 3.94, 4.12, 9.88 mg/L respectively. So the mature larvae still showed high toxicity to chlorfenapyr.3. The temperature effect of chlorfenapyr was investigated. The toxicity of the fourth instar larvae of B. odoriphaga were measured under 8?,16? and 24?. The results demonstrated that the toxicity showed increasing tend with the temperature increasing. Then chlorfenapyr showed positive effect.4. The sublethal concentration(LC1, LC20 and LC50)were determined by stomach and contact joint toxicity method. The results showed that the development duration had no significant difference between treatments and control. But the fecundity was influenced significantly. The LC50 treatment had no effect on fecundity(52.64 eggs/female) and was not significantly different from the control(55.21 eggs/female). However, the LC1 and LC20 treatments(76.25 and 66.59 eggs/female, respectively) were significantly increased. The activities of detoxification enzyme and the amount of energy substance were all influenced in different degree which were treated by sublethal concentration of chlorfenapyr after 24 h. The activities of detoxification enzyme were all increased under all the treatments. And the activity of mixed-functional oxidase-O-demethylation increased as the concentration increased. However, the activity of GST and Car E showed opposite trend. The influence of energy substance showed different trend. The amount of carbohydrates and lipids were decreased significantly and the total proteins which are structure substance were increased. Food consumption were all influenced in different degree after treated by LC1, LC20 and LC50. Under the LC20 treatment, food consumption increased, but not significantly after 48 h. Under the LC50 treatment there was no significant difference in food consumption from the control. Pupal weights were also influenced and showed the same trend as food consumption.5. Absorption and mobility of three formulation chlorfenapyr in different soils were determined by oscillation equilibrium experiment, soil thin layer chromatography and soil column leaching method. The results demonstrated that chlorfenapyr is one kind of medium to extremely easy adsorption and difficult leaching pesticides. The order of leaching between three kinds of formulation: SC > WG > GR; The order of leaching between four kinds of soils: Sandy soil > Yellow loamy soil > Yellow clay soil > Shajiang black soil.6. The degradation dynamics of chlorfenapyr in Chinese chive field, residual quantity in Chinese chive plant and control effect of B. odoriphaga were all evaluatede to analyze the feasibility of chlorfenapyr against B. odoriphaga applied in the field. This present paper compared precision pesticide application(spray and spread with fine soil) and application with irrigation water, and confirmed the formulation, dosage and pesticide application method. The degradation dynamics of chlorfenapyr in Chinese chive field showed no significant difference between treatments, and the half-life period(t1/2) was between 13.54 d to 20.75 d. The concentration of chlorfenapyr in Chinese chive plant were all below determinable level(BDL). The results showed that SC and WG had better control effect than GR, and the application with irrigation water was lower than other treatments. |
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