• Korean Journal of Environmental Agriculture
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• v.39 no.1
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• pp.75-82
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• 2020

BACKGROUND: This study was carried out to establish pre-harvest residue limits (PHRLs) of indoxacarb and pymetrozine in broccoli under greenhouse conditions, based on dissipation patterns and biological half-lives of pesticides during 10 days after application. METHODS AND RESULTS: The field studies were conducted in two different greenhouse, located in Chungju-si (Field 1) and Gunsan-si (Field 2). Samples were collected at 0, 1, 2, 3, 5, 7 and 10 days after spraying pesticide suspension. The analytical methods for indoxacarb and pymetrozine using HPLC-DAD were validated by recoveries ranging of 94.3-105.4% and 81.8-96.0%, respectively, and MLOQ (Method Limit of Quantification) of 0.05 mg/kg. Biological half-lives of indoxacarb and pymetrozine were 2.9 and 3.2-3.8 days in broccoli, respectively. The lower 95% confidence intervals of dissipation rate constant of indoxacarb were determined as 0.1508 (Field 1) and 0.2017 (Field 2), whereas those of pymetrozine were calculated as 0.1489 (Field 1) and 0.1577 (Field 2). CONCLUSION: The significant differences were not observed between the dissipation rates of indoxacarb and pymetrozine in broccoli. The major factor affecting residue dissipation was the dilution effect by fast growth. The PHRLs for 10 days prior to harvest were recommended as 30.06 (Field 1) and 18.07 (Field 2) mg/kg for indoxacarb, and 4.84 (Field 1) and 4.43 (Field 2) mg/kg for pymetrozine, respectively.

• Journal of Applied Biological Chemistry
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• v.63 no.3
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• pp.267-274
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• 2020

The dissipation characteristics and kinetics of fungicide mandipropamid and insecticide thiamethoxam in lettuce under greenhouse conditions were investigated at three different lettuce-growing fields for estimating the pre-harvest residue limits (PHRLs). The analytical methods were fully validated for the quantitation of pesticide residues using High-Performance Liquid Chromatography-Photo Diode Array detector or Ultraviolet-Visible Detector and applied to real samples. The lettuces suitable for shipment were harvested during 10 days including pre-harvest interval after treatment at the recommended dose by safe-use guidelines. The initial mean residues in different fields were 6.68-17.87 and 4.96-8.31 mg/kg for mandipropamid and thiamethoxam, respectively, which decreased to 16-54 and 14-44% in 10 days. The clothianidin, a metabolite of thiamethoxam, was detected in <0.02 to 0.37 mg/kg. The dissipation of both pesticides followed first-order kinetics over a period of 10 days after application. Based on the residue data, the mean dissipation rate constant (λ) and biological half-lives (T_1/2) were estimated to be -0.1060 and 6.5 days of mandipropamid and -0.1236 and 5.6 days of thiamethoxam. The PHRLs for lettuce on the 10th and 5th day before harvesting were calculated to be 63.24 and 43.56 mg/kg for mandipropamid, and 44.66 and 25.88 mg/kg for thiamethoxam, with -0.0746 and -0.1091 of the upper 95% confidence intervals of dissipation rate constant, respectively. This work would be useful as guidance for adjusting the shipment date and contribute to stabilizing the income of farmers in Korea.

• The Korean Journal of Pesticide Science
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• v.16 no.2
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• pp.98-108
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• 2012

In order to use in the classification of minor crop for the mutual application of safe use guideline, it was investigated the residue property of fungicide boscalid and fludioxonil at the same time harvest leafy-vegetables, such as spinach, ulgaribaechu, vitaminchae and cheongkyungchae. After pesticides were applied 2 times with 1 week interval in that day of harvest, 2 days, 5 days and 7 days before harvest, vegetables were harvested, and the residue of pesticides was investigated. Base on the residue in that day of harvest, the deposit of spray solution in vegetables was calculated. The deposit of spray solution of boscalid was 253.9 mL/kg in spinach, 83.0 mL/kg in ulgaribaechu, 97.8 mL/kg in vitaminchae, and 88.3 mL/kg in cheongkyungchae, respectively. In case of fludioxonil, it was calculated 157.6 mL/kg in spinach, 67.6 mL/kg in ulgaribaechu, 64.8 mL/kg in vitaminchae, and 66.6 mL/kg in cheongkyungchae, respectively. When the amount of the deposit of both pesticides was compared in leafy-vegetables, it was the highest in the spinach. On the other hand, it was estimated the predicted dissipation curve of pesticides in leafy-vegetables during cultivation. The half-life of boscalid was 5.9 days in spinach, 7.4 days in ulgaribaechu, 4.6 days in vitaminchae, and 4.3 days in cheongkyungchae, respectively. Also, it was estimated half-life in fludioxonil, it was 3.0 days in spinach, 4.0 days in ulgaribaechu, 3.2 days in vitaminchae, and 3.5 days in cheongkyungchae, respectively. The half-life was the longest in the ulgaribaechu. When both pesticides were compared with the residue property, the deposit of spray solution and half-life of dissipation of boscalid were more than those of fludioxonil.

• Korean Journal of Environmental Agriculture
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• v.37 no.3
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• pp.213-220
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• 2018

BACKGROUND: This study was carried out to determine characteristics of residual pesticides in time-dependent manner and calculate half-lives of the residual pesticides in fresh and dried Chinese matrimony vine. In addition, processing factors were calculated based on the residual concentrations in them. METHODS AND RESULTS: The test pesticides, etofenprox and fenitrothion, were sprayed onto the Chinese matrimony vine plants at once or twice (at seven-day interval) and then samples were collected at 0 (after 3 hours), 1, 3, 5 and 7 days after the last spraying. Dried samples were prepared in hot-air drying oven at $60^{\circ}C$ for 48 hours until water content of less than 20%. Residual concentrations of etofenprox in fresh and dried samples decreased by 54.0-60.9% after 7 days of the last pesticide-application. In case of fenitrothion, the concentrations were found to have decreased by 69.2-76.5%. Processing factors of etofenprox were 2.6-3.0 for the one-time spraying and 2.5-3.0 for the two-time spraying and those of fenitrothion were found to be 1.5-22 for the one-time spraying and 1.6-2.0 for the two-time spraying. First half-lives of etofenprox and fenitrothion in fresh and dried samples ranged from 5.0 to 6.3 and from 3.4 to 4.0 days, respectively. The third half-lives were found to be 15.0-18.9 and 10.2-12.1 days, respectively. CONCLUSION: Residual concentrations of the tested pesticides in the studied crop decreased, but those in the dried samples appeared to have increased. In addition, processing factor and half life were constant regardless of spraying times.

• The Korean Journal of Pesticide Science
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• v.16 no.4
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• pp.328-335
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• 2012

In order to use in the classification of minor crop for the mutual application of safe use guideline, it was investigated the residue property of fungicide dimethomorph and pyraclostrobin in green onion, a stem-crop. After pesticides were applied 2 times with 1 week interval in that day of harvest, 3 days, 7 days, 10 days and 14 days before harvest, a green onion was harvested. The residue of dimethomorph in a green onion was 26.31 and 39.08 mg/kg in that day of harvest, however, in according to elapse time, it was reduced to 6.86 and 9.34 mg/kg in 14 days before harvest. In case of pyraclostrobin, it was also reduced from 13.46 and 39.08 mg/kg to 3.57 and 5.21 mg/kg. Based on the residue in that day of harvest, the deposit of spray solution in a green onion was calculated. The deposit of spray solution of dimethomorph was 274.35~345.84 mL/kg, in case of pyraclostrobin, it was calculated 213.65~343.33 mL/kg. When the amount of the deposit of both pesticides was compared in a green onion, it was so similar. On the other hand, it was estimated the predicted dissipation curve of pesticides in the green onion during cultivation. The half-life of dimethomorph was 6.95~7.45 days, in case of pyraclostrobin, 7.15~7.45 days. When both pesticides were compared with the residue property, the deposit of spray solution and half-life of dissipation were so similar.

• Journal of Applied Biological Chemistry
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• v.55 no.4
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• pp.235-239
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• 2012

While cultivating crops, it is important to predict the biological half-lives of applied pesticides to ensure the safety of agricultural products. Dissipation patterns of the triazole fungicides, such as diniconazole and metconazole, during the cultivation of apple were established by utilizing the dissipation curve. As well as, the biological half-lives of the pesticides in apples were calculated using the residue amounts of them. The apples were harvested from 0 to 14 days after spraying diniconazole (WP) and metconazole (SC) at a recommended and three times of the recommended dose. Initial concentrations of diniconazole in apple were 0.09 and 0.15 mg/kg at a recommended and three times of the recommended dose, respectively, which were below MRL 1.0 mg/kg established by KFDA. The equations of biological half-life were $C_t=0.0811e^{-0.179x}$(half life: 3.9 days) and $C_t=0.1451e^{-0.148x}$ (half life: 4.7 days), respectively. In case of metconazole, initial concentrations in apple were 0.10 and 0.25 mg/kg, below MRL 1.0mg/kg, and biological half-life equations were $C_t=0.0857e^{-0.055x}$ (half life: 12.6 days) and $C_t=0.2304e^{-0.052x}$ (half life: 13.3 days), respectively. Therefore, when triazole fungicides were applied during the cultivation of apple, the biological half-life need to be calculated with the optimal equation model.

• The Korean Journal of Pesticide Science
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• v.12 no.1
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• pp.74-81
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• 2008

To elucidate the exposure of pesticide in agricultural environment and to investigate distribution of pesticide in paddy fields. This experiment was carried out to clarify pesticide distribution in paddy fields applied with different formulations and growing stages. Initial dissipation rate of applied butachlor EW and oxadiazon EC before rice planting were more than 90% within 3 days in paddy fields. The distribution of a.i. in the pesticide formulations tested depended upon the elapsed time at each growing stage of rice plant after application. Most of pesticides applied within 15 days after transplanting of rice seedlings, more than 95%, were located in the surface water and soil regardless of pesticides; butachlor, thiobencarb and molinate GR. The distribution of iprobenfos GR, tricyclazole WP and phenthoate EC, after application 2 hours in middle growing stage (46 days after rice planting) were shown as 16.1, 48.9 and 38.9% in surface water, 83.6, 15.4 and 10.7% in soil, and 0.3, 35.7 and 50.4% in rice plants of paddy fields, respectively. Also tricyclazole WP and phenthoate EC, after application 2 hours in the late rice growing stage (90 days after rice planting) were distributed to 7.8 and 9.8% in surface water, and 21.7 and 5.1% in soil, and 70.5 and 85.1% in rice plants of paddy fields, respectively.

• Korean Journal of Environmental Agriculture
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• v.28 no.3
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• pp.281-288
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• 2009

The strobilurin fungicides, azoxystrobin and kresoxim-methyl, were investigated to know the biological half-lives and dissipation patterns in Korean melon under plastic film house condition. Used pesticides for field application were 20% azoxystrobin of suspension concentrate and 47% kresoxim-methyl of water dispersible granule. Two pesticides were sprayed at recommended and double dose rate. Pesticide residues in Korean melon were analyzed until 14 days after application. The azoxystrobin was analyzed by HPLC equipped with UV detector after cleanup with florisil glass column. Initial residue concentrations of azoxystrobin in Korean melon at recommended and double dose rate were 0.09 mg/kg and 0.14 mg/kg, respectively. Those were less than 0.2 mg/kg maximum residue limit of Korean melon established by KFDA. The biological half-lives of azoxystrobin in Korean melon were 4.7 days at recommended dose rate and 7.8 days at double dose rate. Initial concentrations of kresoxim-methyl which was analyzed by GLC-ECD in Korean melon at recommended and double dose rate were 0.10 mg/kg and 0.23 mg/kg, respectively. Those were less than 1.0 mg/kg, MRL. The biological half-lives of kresoxim-methyl in Korean melon were 4.1 days at recommended dose rate and 4.8 days at double dose rate. The residue amounts of both pesticide was lower than MRL and biological half-lives were not so long. Because the weight of Korean melon under plastic film house condition was fast increased during cultivation.

• The Korean Journal of Pesticide Science
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• v.17 no.1
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• pp.6-12
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• 2013

Methoxyfenozide and novaluron were sprayed with single and triple treatments separately on peach during cultivation period. Samples were collected over 14 days, 8 times in total (0, 2, 4, 6, 8, 10, 12, 14 days). Methoxyfenozide and novaluron were extracted with acetone and partitioned with dichloromethane, and analyzed by HPLC/DAD. Method Quantitation Limit (MQL) were both 0.005 mg/kg, average recoveries of methoxyfenozide at two fortification levels of 0.05 and 0.25 mg/kg were determined $92.7{\pm}2.9%$ and $102.8{\pm}3.1%$, and novaluron were $98.2{\pm}4.8%$ and $96.7{\pm}9.0%$, respectively. The biological half-life of methoxyfenozide was about 4.41 days at single treatment, and 4.24 days at triple treatments. The biological half-life of novaluron was about 14.81 days at single treatment, and 14.50 days at triple treatments. Dissipation of pesticides on peach was influenced by growth dilution effect. In case of application of methoxyfenozide and novaluron following guidelines on safe use of pesticides, the final residue level was predicted to be lower than Maximum Residue Limit (MRL).

• Korean Journal of Environmental Agriculture
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• v.9 no.1
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• pp.9-13
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• 1990

The dissipation of insecticide fenitrothion(O,O-dimethyl O-4-nitro-m-tolyl phosphorothioate), fungicide IBP(S-benzyl O, O-diisopropyl phosphorothioate), and herbicide butachlor(N-butozymethyl-2-chloro-2', 6'-diethylacetanilide) in flooded soil planted with rice plants was investigated in outdoor pot conditions. The half lives of IBP, butachlor and fenitrothion in the flooding water treated with IBP at 98g, butachlor at 352.8g, and fenitrothion at 100g ai/10a, were 3.6, 1.7 and within 1 day, respectively. The concentration of fenitrothion at 5 days after application was found to be less than 0.0lppm. In the case of IBP and butachlor after 20 days, the concentration was 0.025 and 0.004ppm, respectively. The concentration of fenitrothion, IBP, butachlor in a soil depth of 0-3cm was 0.07, 1.45 and 3.37ppm on the 3rd day after application, and below 0.05, 0.18, 0.39ppm after 7 days, respectively. However, 27 days after application concentration of IBP and butachlor at 0-5cm soil depth resulted in 0.04 and 0.05ppm, respectively. The disappearance of pesticides was remarkably rapid, compared to those in the some soil under the laboratory conditions. Differences in the concentration of IBP in different soil profiles were few, but amounts of butachlor were remarkably higher at 0-2cm soil depth than below 2cm soil depth.