[ Objective] To overcome the resistance of Phytophthora parasitica var. nicotianae against metalaxyl and effectively control its damage, new efficient complex agent of metalaxyl was studied and developed. [ Method] Th...[ Objective] To overcome the resistance of Phytophthora parasitica var. nicotianae against metalaxyl and effectively control its damage, new efficient complex agent of metalaxyl was studied and developed. [ Method] The toxieities of nine fungicides against P. parasitica were measured using growth rate method. On this basis, the fungicides with good effects were selected to compound with metalaxyl, and the optimum complex ratio was confirmed. [Result] The toxicity of metalaxyl was the strongest with EC50 of 2. 130 5μg/ml; followed by carbendazim, mancezeb and dimethomorph with EC50 of 2.357 9, 2.639 8 and 2. 778 8 μg/ml. The effect of cyazofamid was the poorest with EC50 of 6. 278 8 μg/ml. The optimum complex ratios of dimethomorph, carbendazim and mancezeb with metalaxyl were 40： 60, 30：70 and 20： 80, and their co-toxicity coefficients were 138.80,124.25 and 115.00, respectively. [ Conclusion] The complex agents had application and promotion value, which could be used to carry out further field trials.展开更多
The proportion of organic matter and mineral composition are important factors determining the formation and type of non-extractable residues(NERs) of pesticides in soil. In this study, we investigated the enantiosele...The proportion of organic matter and mineral composition are important factors determining the formation and type of non-extractable residues(NERs) of pesticides in soil. In this study, we investigated the enantioselectivity in degradation and NER formation of the chiral fungicide metalaxyl in soil particle size fractions(silt and clay). Microbial and extracellular enzyme activities during these processes were monitored in incubation of silt and clay samples isolated from sterilized and non-sterilized soil samples collected from a long-term agricultural field experimental site in Ultuna, Sweden. The temporal influence on the fate of the fungicide was noted by short-term(10-d) and long-term(92-d) incubations. Besides the acquisition of quantitative data with gas chromatography-mass spectrometry(GC/MS), stereoselective analyses were performed with chiral GC/MS. Quantitative results pointed to a higher metabolism rate of the pesticide through microbial activity than through extracellular enzyme activity. This was also confirmed by the enantioselective depletion of R-metalaxyl and the subsequent formation of R-metalaxyl acid in microbially active samples from non-sterilized soil. The silt fraction containing a high amount of organic matter exhibited a significant hydrolyzable proportion of metalaxyl NERs that was releasable under alkaline conditions. On the contrary, the clay fraction showed an enhanced affinity for covalently bound residues. Based on our results, we recommend differentiating between reversibly and irreversibly bound proportions of pesticides in persistence and environmental risk assessment because the reversible fraction contained potentially bioavailable amounts of residues that may be released under natural conditions.展开更多
The isolates of Phytophthora infestans on tomato in the Guangxi Zhuang Autonomous Region, China, were determined for the sensitivities to metalaxyl, cymoxanil and dimethomorph to give the basic information for integra...The isolates of Phytophthora infestans on tomato in the Guangxi Zhuang Autonomous Region, China, were determined for the sensitivities to metalaxyl, cymoxanil and dimethomorph to give the basic information for integrating disease management. Sensitivities were tested by measuring the radial growth on agar medium amended with fungicide, compared with the floating-leaf-disk method. 239 isolates were collected from eight tomato growing areas during 2000-2006. The testing results indicated that the frequencies of sensitive, intermediate, and resistant isolates to metalaxyl were 42.26, 35.98, and 23.53%, respectively. Variations in sensitivities amongst isolates from different areas or different years were very high for metalaxyl. All isolates from Tianlin and Wuxuan were sensitive to metalaxyl, but the metalaxyl-resistant isolates predominated in Tianyang, with the frequency of 51.35%. The EC50 values of certain isolates from Tianyang were higher than 500 μg·mL^-1 and their resistance levels were over 100 000 folds. Cymoxanil has been used for nearly 10 years in Guangxi, and dimethomorph has been used for 5-6 years. However, there was no decrease in sensitivity of P. infestans populations and the sensitivities of the pathogen were nearly normally distributed. Hence, their mean ECs0 value [cymoxanil （0.1647 ±0.0255） μg·mL^-1, dimethomorph （0.0970 ± 0.0052） μg·mL^-1 could be used as the baseline sensitivities for monitoring the field resistance development. The comparison with the floating-leaf-disk method indicates that both the techniques provided equivalent results. These studies suggested that metalaxyl can be continuously applied in Tianlin, Wuxuan, and Nanning due to the resistant isolates that have not been found, while for those areas with resistant isolate, the use of metalaxyl should be reduced or alternated, and cymoxanil or dimethomorph was recommended for controlling late blight disease of tomato.展开更多
Four microorganisms, Pseudomonas sp. （ER2）, Aspergillus niger （ER6）, Cladosporium herbarum （ER4） and Penicilluim sp. （ER3）, were isolated from cucumber leaves previously treated with metalaxyl using enrichment...Four microorganisms, Pseudomonas sp. （ER2）, Aspergillus niger （ER6）, Cladosporium herbarum （ER4） and Penicilluim sp. （ER3）, were isolated from cucumber leaves previously treated with metalaxyl using enrichment technique. These isolates were evaluated for detoxification of metalaxyl at the recommended dose level in aquatic system. The effect of pH and temperature on the growth ability of the tested isolates was also investigated by measuring the intracellular protein and mycelia dry weight for bacterial and fungal isolates, respectively. Moreover, the toxicity of metalaxyl after 28 d of treatment with the tested isolates was evaluated to confirm the complete removal of any toxic materials （metalaxyl and its metabolites）. The results showed that the optimum degree pH for the growth of metalaxyl degrading isolates （bacterial and fungal isolates） was 7. The temperature 30℃ appeared to be the optimum degree for the growth of either fungal or bacterial isolates. The results showed that Pseudomonas sp. （ER2） was the most effective isolate in metalaxyl degradation followed by Aspergillus niger （ER6）, Cladosporium herbarum （ER4） and Penicilluim sp. （ER3）, respectively. There is no toxicity of metalaxyl detected in the supematant after 28 d of treatment with Pseudomonas sp. （ER2）. The results suggest that bioremediation by Pseudomonas sp. （ER2） isolate was considered to be effective method for detoxification of metalaxyl in aqueous media.展开更多
A determination method for metalaxyl （MEL） residues in watermelon and banana had been established by automated solid-phase extraction （SPE） cou- pled with high performance liquid hromatography （HPLC）. Samples we...A determination method for metalaxyl （MEL） residues in watermelon and banana had been established by automated solid-phase extraction （SPE） cou- pled with high performance liquid hromatography （HPLC）. Samples were extracted by acetonitrile, homogenized, filtrated, extracted by automated solid-phase ex- traction （SPE）, and finally purified by C18 column. The experiment was carried on SunFireTM C18 column with the mobile phase of acetonitrile-water-methanol （25： 40： 35, by vol） at the flow rate of 1.0 mL/min. The detection wavelength and injection volume were set at 220 nm and 10 uL, respectively. The recoveries of three different concentrations （0.02, 0.20, 1.00 mg/kg） for watermelon and banana were 94.3 % - 101.0% and 81.5% - 99.6%, respectively. RSD （ n = 5 ） were 1.30% -5.29% and 2.66% -6.67%, respectively. The lower detection limit for metalaxyl was 0. 006 mg/kg. This method met with the requirements of pesticide residue detection. Key words Metalaxyl; HPLC; Watermelon; Banana展开更多
The control effect of 68% Metalaxyl-M·Mancozeb WDG against Dendrobium officinale blight was studied. The results showed that the control effect of 68% Metalaxyl-M·Mancozeb WDG at the dose of 1 133-1 360 mg/k...The control effect of 68% Metalaxyl-M·Mancozeb WDG against Dendrobium officinale blight was studied. The results showed that the control effect of 68% Metalaxyl-M·Mancozeb WDG at the dose of 1 133-1 360 mg/kg against D. officinale blight was over 78.4% at 14 d post spraying, which was equivalent to that of control agent 72% Cymoxanil·Mancozeb WP(1 200 mg/kg) and 80% Mancozeb WP(1 143 mg/kg).Therefore, 68% Metalaxyl-M·Mancozeb WDG sprayed at the dose of 1 133-1 360 mg/kg could effectively control the damage of D. officinale blight.展开更多
基金Supported by Key Project of Sichuan Education Department "Study on Physiological Race of Tobacco Black Shank in Liangshan and Resistance Evaluation of Tobacco Germplasm Resources in Sichuan Province"(08ZA032)~~
文摘[ Objective] To overcome the resistance of Phytophthora parasitica var. nicotianae against metalaxyl and effectively control its damage, new efficient complex agent of metalaxyl was studied and developed. [ Method] The toxieities of nine fungicides against P. parasitica were measured using growth rate method. On this basis, the fungicides with good effects were selected to compound with metalaxyl, and the optimum complex ratio was confirmed. [Result] The toxicity of metalaxyl was the strongest with EC50 of 2. 130 5μg/ml; followed by carbendazim, mancezeb and dimethomorph with EC50 of 2.357 9, 2.639 8 and 2. 778 8 μg/ml. The effect of cyazofamid was the poorest with EC50 of 6. 278 8 μg/ml. The optimum complex ratios of dimethomorph, carbendazim and mancezeb with metalaxyl were 40： 60, 30：70 and 20： 80, and their co-toxicity coefficients were 138.80,124.25 and 115.00, respectively. [ Conclusion] The complex agents had application and promotion value, which could be used to carry out further field trials.
基金Financial support by the German Research Foundation (DFG) (SCHW750/9) in the frame of the Priority Program SPP 1315。
文摘The proportion of organic matter and mineral composition are important factors determining the formation and type of non-extractable residues(NERs) of pesticides in soil. In this study, we investigated the enantioselectivity in degradation and NER formation of the chiral fungicide metalaxyl in soil particle size fractions(silt and clay). Microbial and extracellular enzyme activities during these processes were monitored in incubation of silt and clay samples isolated from sterilized and non-sterilized soil samples collected from a long-term agricultural field experimental site in Ultuna, Sweden. The temporal influence on the fate of the fungicide was noted by short-term(10-d) and long-term(92-d) incubations. Besides the acquisition of quantitative data with gas chromatography-mass spectrometry(GC/MS), stereoselective analyses were performed with chiral GC/MS. Quantitative results pointed to a higher metabolism rate of the pesticide through microbial activity than through extracellular enzyme activity. This was also confirmed by the enantioselective depletion of R-metalaxyl and the subsequent formation of R-metalaxyl acid in microbially active samples from non-sterilized soil. The silt fraction containing a high amount of organic matter exhibited a significant hydrolyzable proportion of metalaxyl NERs that was releasable under alkaline conditions. On the contrary, the clay fraction showed an enhanced affinity for covalently bound residues. Based on our results, we recommend differentiating between reversibly and irreversibly bound proportions of pesticides in persistence and environmental risk assessment because the reversible fraction contained potentially bioavailable amounts of residues that may be released under natural conditions.
文摘The isolates of Phytophthora infestans on tomato in the Guangxi Zhuang Autonomous Region, China, were determined for the sensitivities to metalaxyl, cymoxanil and dimethomorph to give the basic information for integrating disease management. Sensitivities were tested by measuring the radial growth on agar medium amended with fungicide, compared with the floating-leaf-disk method. 239 isolates were collected from eight tomato growing areas during 2000-2006. The testing results indicated that the frequencies of sensitive, intermediate, and resistant isolates to metalaxyl were 42.26, 35.98, and 23.53%, respectively. Variations in sensitivities amongst isolates from different areas or different years were very high for metalaxyl. All isolates from Tianlin and Wuxuan were sensitive to metalaxyl, but the metalaxyl-resistant isolates predominated in Tianyang, with the frequency of 51.35%. The EC50 values of certain isolates from Tianyang were higher than 500 μg·mL^-1 and their resistance levels were over 100 000 folds. Cymoxanil has been used for nearly 10 years in Guangxi, and dimethomorph has been used for 5-6 years. However, there was no decrease in sensitivity of P. infestans populations and the sensitivities of the pathogen were nearly normally distributed. Hence, their mean ECs0 value [cymoxanil （0.1647 ±0.0255） μg·mL^-1, dimethomorph （0.0970 ± 0.0052） μg·mL^-1 could be used as the baseline sensitivities for monitoring the field resistance development. The comparison with the floating-leaf-disk method indicates that both the techniques provided equivalent results. These studies suggested that metalaxyl can be continuously applied in Tianlin, Wuxuan, and Nanning due to the resistant isolates that have not been found, while for those areas with resistant isolate, the use of metalaxyl should be reduced or alternated, and cymoxanil or dimethomorph was recommended for controlling late blight disease of tomato.
文摘Four microorganisms, Pseudomonas sp. （ER2）, Aspergillus niger （ER6）, Cladosporium herbarum （ER4） and Penicilluim sp. （ER3）, were isolated from cucumber leaves previously treated with metalaxyl using enrichment technique. These isolates were evaluated for detoxification of metalaxyl at the recommended dose level in aquatic system. The effect of pH and temperature on the growth ability of the tested isolates was also investigated by measuring the intracellular protein and mycelia dry weight for bacterial and fungal isolates, respectively. Moreover, the toxicity of metalaxyl after 28 d of treatment with the tested isolates was evaluated to confirm the complete removal of any toxic materials （metalaxyl and its metabolites）. The results showed that the optimum degree pH for the growth of metalaxyl degrading isolates （bacterial and fungal isolates） was 7. The temperature 30℃ appeared to be the optimum degree for the growth of either fungal or bacterial isolates. The results showed that Pseudomonas sp. （ER2） was the most effective isolate in metalaxyl degradation followed by Aspergillus niger （ER6）, Cladosporium herbarum （ER4） and Penicilluim sp. （ER3）, respectively. There is no toxicity of metalaxyl detected in the supematant after 28 d of treatment with Pseudomonas sp. （ER2）. The results suggest that bioremediation by Pseudomonas sp. （ER2） isolate was considered to be effective method for detoxification of metalaxyl in aqueous media.
文摘A determination method for metalaxyl （MEL） residues in watermelon and banana had been established by automated solid-phase extraction （SPE） cou- pled with high performance liquid hromatography （HPLC）. Samples were extracted by acetonitrile, homogenized, filtrated, extracted by automated solid-phase ex- traction （SPE）, and finally purified by C18 column. The experiment was carried on SunFireTM C18 column with the mobile phase of acetonitrile-water-methanol （25： 40： 35, by vol） at the flow rate of 1.0 mL/min. The detection wavelength and injection volume were set at 220 nm and 10 uL, respectively. The recoveries of three different concentrations （0.02, 0.20, 1.00 mg/kg） for watermelon and banana were 94.3 % - 101.0% and 81.5% - 99.6%, respectively. RSD （ n = 5 ） were 1.30% -5.29% and 2.66% -6.67%, respectively. The lower detection limit for metalaxyl was 0. 006 mg/kg. This method met with the requirements of pesticide residue detection. Key words Metalaxyl; HPLC; Watermelon; Banana
文摘The control effect of 68% Metalaxyl-M·Mancozeb WDG against Dendrobium officinale blight was studied. The results showed that the control effect of 68% Metalaxyl-M·Mancozeb WDG at the dose of 1 133-1 360 mg/kg against D. officinale blight was over 78.4% at 14 d post spraying, which was equivalent to that of control agent 72% Cymoxanil·Mancozeb WP(1 200 mg/kg) and 80% Mancozeb WP(1 143 mg/kg).Therefore, 68% Metalaxyl-M·Mancozeb WDG sprayed at the dose of 1 133-1 360 mg/kg could effectively control the damage of D. officinale blight.
