| Coptotermes formosanus is the main population of Haikou City, which is seriously harmful to building and forestry. Its eradication and prevention are still based on the use of chemical agents. Chlorpyrifos, Bifenthrin, Lambda-cyhalothrin, Beta cypermethrin Abamectin, Phoxim and Imidacloprid are the termite control drugs, which have been widely used. Red loam, coastal sandy soil and banded tidal mud were chosen as test soils,which are distributed in the surrounding buildings of Haikou city. The biological activity of the above seven pesticides to C. formosanus was determined by the impregnated filter method and toxic soil penetration method, including contact toxicity of termites to the above drugs and penetrability of termites in the poison soil. At the same time, the residue and degradation of pesticides in the soil were studied. The results are as follow:(1) The test result showed that the tested standard pesticides were to C. formosanus via the impregnated filter method: in seven pesticides, the lowest median lethal concentration (LC50) to C. formosanus was 98.4% Phoxim, and the highest is 98.6% Beta cypermethrin, reaching to 1.677 mg/L and 16.545 mg/L respectively. LC50 to C. formosanus of 99.0% Chlorpyrifos, 98.7% Lambda-cyhalothrin, 98.5% bifenthrin, 95.0%Abamectin and 98.0% imidacloprid were 2.769mg/L, 3.673 mg/L, 3.822 mg/L, 7.006mg/L and 10.280mg/L respectively. Therefore it can be seen that the biological activity order of the standard reagent for C. formosanus: 98.4% Phoxim > 99.0% Chlorpyrifos > 98.5%Bifenthrin > 98.7% lambda-cyhalothrin > 95.0% Abamectin > 98.0% Imidacloprid > 98.6%beta cypermethrin.(2) The test result showed that the tested standard pesticides were to C. formosanus via rate of mortality and kockdown: the minimum effective concentration (MEC) of 99%chlorpyrifos to C.formosanus was 7.813mg/L,and median of knockdown time (KT50)was in 1h?2h; the MEC of 98.6% Beta cypermethrin to C. formosanus was 6.250mg/L,and KT50 was in 0.5h; the MEC of 98.7% Lambda-cyhalothrin to C. formosanus was 3.125mg/L, and KT50 was in 0.5h; the MEC of 98.5% Bifenthrin to C. formosanus was 25mg/L,and KT50 was in 0.5h?1h; the MEC of 95% Abamectin to C. formosanus was 60mg/L, and KT50 was in 0.5h?1h; the MEC of 98.4% Phoxim to C.formosanus was 3.125mg/L, and KT50 was in 3h?12h; the MEC of 98.0% Imidacloprid to C. formosanus was 62.500mg/L, and KT50 was beyond 12h.(3) The test result showed that the tested commodity chemical pesticides were to C.formosanus via the impregnated filter method: in seven pesticides, the lowest LC50 to C. formosanus was 4.5% Beta cypermethrin EC, and the highest is 10% Imidacloprid WP,reaching to 1.123mg/L and 117.975mg/L respectively. LC50 to C.formosanus of 45%Chlorpyrifos EC, 2.5% Lambda-cyhalothrin EC, 10% Bifenthrin EC, 40% Phoxim EC and 5% Abamectin EC were 9.057mg/L, 4.909 mg/L, 27.422mg/L, 17.516mg/L and 4.813mg/L, respectively. Thus it can be seen that the biological activity order of the commodity chemical reagent for C. formosanus: 4.5% Beta cypermethrin EC> 40%Phoxim EC > 2.5% Lambda-cyhalothrin > 45% Chlorpyrifos EC> 5% Abamectin EC >10%Bifenthrin EC > 10% Imidacloprid WP.(4) The test result showed that the tested commodity chemical pesticides were to C.formosanus via rate of mortality and kockdown: the MEC of 40% Chlorpyrifos EC to C.formosanus was 7.031 mg/L, and KT50 was in 0.75h; the MEC of 4.5% Beta cypermethrin EC to C.formosanus was 1.406mg/L,and KT50 was in 0.5h?1h; the MEC of 2.5%Lambda-cyhalothrin EC to C. formosanus was 6.250mg/L, and KT50 was in 0.5h?1h; the MEC of 10% Bifenthrin EC to C. formosanus was 62.500mg/L, and KT50 was beyond 3h;the MEC of 5% Abamectin EC to C. formosanus was 15.625mg/kg, and KT50 was in 12h?24h; the MEC of 40% Phoxim EC to C. formosanus was 6.250mg/kg,and KT50 was in 3?6h; the MEC of 10% Imidacloprid WP to C. formosanus was 62.500mg/kg,and KT50 was in 0.5h.(5) In toxic soil penetration test of the standard drug, the MEC of 7 kinds of tested pesticides to C. formosanus were that 99.0% Chlorpyrifos, 98.6% Beta cypermethrin, 98.7%Lambda-cyhalothrin, 98.5% Bifenthrin, 95% Abamectin, 98.4% Phoxim, and 98.0%Imidacloprid were 62.500 mg/kg, 100mg/kg, 200mg/kg, 25mg/kg, 250mg/kg, 100 mg/kg,and 500 mg/kg respectively. Acordingly it can be seen that the biological activity order of the standard reagent for C. formosanus by toxic soil penetration test method: 98.5%Bifenthrin > 99.0% Chlorpyrifos > 98.4% Phoxim > 98.6% Beta cypermethrin > 98.7%lambda-cyhalothrin > 95% Abamectin > 98.0% Imidacloprid.(6) In toxic soil penetration test of the commodity chemical drug, the MEC of 7 kinds of tested pesticides to C. formosanus were that 45% Chlorpyrifos EC, 4.5% Beta cypermethrin EC, 2.5% Lambda-cyhalothrin EC, 10% Bifenthrin EC, 5% Abamectin EC,40% Phoxim EC, and 10% Imidacloprid WP were 7.031mg/kg, 25mg/kg, 22.500mg/kg,125mg/kg, 15.625mg/kg, 6.250mg/kg, and 125mg/kg respectively. Hence it can be seen that the biological activity order of the commodity chemical reagent for C. formosanus by toxic soil penetration test method: 40% Phoxim EC > 99.0% Chlorpyrifos EC > 5%Abamectin EC > 2.5% Lambda-cyhalothrin EC > 4.5% Beta cypermethrin EC > 10%Bifenthrin EC > 10% Imidacloprid WP.(7) Pesticide residue and degradation test showed that: It was consistent that the degradation of the seven standard chemical pesticides was in the indoor soil, and the degradation rate in the sterilized soil is slower than that in the non-sterile soil. 99.0%Chlorpyrifos, 98.5% Bifenthrin, 98.7% Lambda-cyhalothrin, 98.6% B-cypermethrin, 95%Avermectin, 98.4% Phoxim and 98.0% Imidacloprid were added in red soil, sandy soil and banded tidal soil with bacteria and sterile environment. The results showed that the degradation half-lives were in the range of 4.076d ?6.930d, 6.930d ?13.860d,4.620d ?7.700d,2.166 ?3.850d,2.475 ?3.647d,3.647 ? 4.950d and 2.038 ?2.475d in the red soil respectively,the degradation half-lives were in the range of 1.359d?9.900d,1.873d?3.647d,1.359d?3.465d,1.733d?4.950d,1.690d?1.873d,2.163d?2.235d and 2.038d?4.076d in the sandy soil respectively, and the degradation half-lives were in the range of 1.359d ?9.900d,1.873d ?3.647d, 1.359d ?3.465d,1.733d ?4.950d, 1.690d ?1.873d,2.163d?2.235d and 2.038d?4.076d in the banded tidal soil respectively.The degradation dynamics of seven kinds of commercial agents were fluctuated by soil physical and chemical properties, weather conditions and so on in the outdoor three soils. 45% Chlorpyrifos EC, 10% Bifenthrin EC, 2.5% Lambad-cyhalothrin EC, 4.5%B-cypermethrin EC, 5% Avermectin EC, 40% Phoxim EC and 10% Imidacloprid WP were sprayed in the red soil, sandy soil, and banded tidal soil. The results showed that the half-lives of degradation in red soil were 64.969d, 50.707d, 79.962d, 43.313d, 71.690d,47.250d and 39.226d, respectively, the half-life of degradation in sandy soil was 39.981d,33.532d, 32.484d, 31.985d, 39.226d, 29.700d and 35.845d respectively, and the degradation half-lives in the banded tidal soils were 34.082d,56.189d,51.975d,33.532d,69.300, 54.711 and 51.975 respectively. |
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