Evaluation Of Soil Chemical Barrier Of Three Preventive Termiticides

At present, chlorpyrifos, bifenthrin, imidacloprid were widely used to control termites. The experiment of soil column, field base test and practical construction site test were used to study the soil permeability and the content threshold of the soil chemical barrier of chlorpyrifos, bifenthrin and imidacloprid.(1) The tests of indoor soil column and outdoor permeability of chlorpyrifos, bifenthrin and imidacloprid showed that optimum sampling depth of 15cm in soil chemical barrier in Yancheng area was recommend.(2) The agent content test in soil chemical barrier was conducted. The results showed that the content in the indoor soil column of chlorpyrifos, bifenthrin and imidacloprid were 138.2mg/kg-378.3 mg/kg,25.6 mg/kg-42.1 mg/kg and 16.1 mg/kg-45.2 mg/kg, respectively. The content in the field soil of chlorpyrifos, bifenthrin and imidacloprid were 119.6 mg/kg-268.5 mg/kg,13.3 mg/kg-36.1 mg/kg and 13.9 mg/kg-37.2 mg/kg, respectively.(3) The results from outdoor degradation test showed that the degradation half-life of chlorpyrifos, bifenthrin and imidacloprid were 118.6-196.3d,192.5-305.4d and 146.9-292. 1d, respectively.(4) Based on the practical operation situation and the sample results after applied for 1-5d, the evaluation standard of soil chemical barrier for the termite prevention in Yancheng area was determined as below:if termiticides are applied according to the recommended use concentration, and then the contents of chlorpyrifos, bifenthrin, imidacloprid in the dry soil are 100～260 mg/kg,7～35 mg/kg,10～35 mg/kg was determined, respectively, the construction quality of the termite prevention is judged as up to standard. If the contents are below the lower limit, it will beyond the reach of the purpose of the control of termites; and if higher than the upper limit, it could be pollute the environment, then the construction quality is judged as disqualification. The construction site experiment using the recommended sampling depth of 15 cm show that the content of the soil chemical barrier of chlorpyrifos, bifenthrin, imidacloprid in Yancheng area confirmed to the limits of the above standard, which could prove that this standard suggested in this paper is reasonable and feasible. The results of this study are useful for ensuring the construction quality of the termite prevention, and reducing the negative effects of chemical agents at the same time, which provide the basis to strengthen the market management of termite prevention.