• The Plant Pathology Journal
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• v.21 no.1
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• pp.33-38
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• 2005

Changes of control efficacy of chemical to potato late blight caused by Phytophthora infestans in potato fields from 2001 to 2004 were examined. Control efficacy of metalaxyl was suddenly decreased from 100% in 2002 to 50% in 2004 and that of dimethomorph also was similar to those of metalaxyl. However, the control efficacy of ethaboxam no great change. Both A1 and A2 mating type isolates were isolated from 2001 to 2004 in several areas in Korea. The majority of the P. infestans isolates were A1 mating type. Total 939 isolates of P. infestans obtained from several areas in Korea from 2001 to 2004 were examined for changes of sensitivity to metalaxyl. Frequencies of metalaxyl resistance isolates were gradually increased from 17% in 2001 to 84.2% in 2004, but isolation frequencies of metalaxyl sensitive and intermediate resistant isolate were decreased. Cause of decreasing control efficacy of metalaxyl was thought by increase of resistance isolates in A1 mating type population according to increasing metalaxyl use. Most isolates were grown at 0.5 ${\mu}g/ml of dimethomorph and isolates grown at 1 ${\mu}g/ml of dimethomorph were approximately 10.2-22.9%. However, no isolate was able to grow at 5.0 ${\mu}g/ml. Based on these results, minimum inhibitory concentrations (MIC) of dimethomorph to P. infestans were determined to be 0.5-1.0 ${\mu}g/ml. Our results indicated that the reason decreasing control efficacy of dimethomorph was not caused by occurrence of resistant isolates. About 5% and 12.1% isolates among the total isolates collected in 2003 and 2004 were grown on V-8 juice rye agar containing 1.0 ${\mu}g/ml ethaboxam. The 2.1 and 25.4% isolates had MICs of 0.2-0.4 ${\mu}g/ml, and MIC values of 87.9% and 74.3% isolates were less than 0.2 ${\mu}g/ml concentrations of ethaboxam. Therefore, resistance development by P. infestans to ethaboxam is not likely to occur in the natural condition.

• Korean Journal Plant Pathology
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• v.10 no.3
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• pp.192-196
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• 1994

Two hundred and fourty-seven isolates of Phytophthora infestans obtained from infested potato leaves from the spring of 1991 to the fall of 1993 from potato fields in various regions of Korea were tested for their fungicides resistances. A total of 20.9% isolates were not suppressed at 50 ppm of metalaxyl in 1991, but isolates from 1993 were suppressed at 50 ppm of metalaxyl. Ten resistant isolates and 10 susceptible isolates to metalaxyl were selected and tested against oxadixyl, fosetyl-Al, and phosphorous acid. Effectiveness of these chemicals were no better than that of metalaxyl. Dimethomorph suppressed all isolates at 1 $\mu\textrm{g}$/ml suggesting that it might be a potential chemical to control Phytophthora infestans. Mating types of all isolates from diseased leaves in 1993 turned out to be A2 type.

• The Korean Journal of Pesticide Science
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• v.6 no.1
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• pp.42-44
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• 2002

A very destructive lily disease was occurred at Daekwallyong alpine areas in 1999. We have performed experiments to identify the causal pathogen of lily disease and to find a way to control the disease chemically. Twelve fungal isolates from the infected lily were identified as Phytophthora cactorum. Mycelial growth of all isolates were completely inhibited on potato dextrose agar with $10{\mu}g/mL$ metalaxyl. Among 11 fungicides tested, $10{\mu}g/mL$ of dimethomorph, ethaboxam, and oxadixyl inhibited mycelial growth of P. cactorum. PC-1. Therefore, spray of phenylamide fungicides such as metalaxyl and other commercial fungicides should be a effective way to control the Phytophthora blight of lily.

• Journal of Applied Biological Chemistry
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• v.65 no.1
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• pp.17-21
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• 2022

A new rapid and simple method for metalaxyl in Atractylodes macrocephala Koidzumi and Achyranthes japonica Nakai has been developed and validated. This study was conducted to develop a method for analyzing metalaxyl by a method based on QuEChERS using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). Samples were extracted with acetonitrile and purified using amino-propyl (NH₂) Solid Phase Extraction cartridge. The method limit of quantitation (MLOQ) was 0.01 mg/kg. The linearity of matrix-matched calibration curve (r²) was ≥0.99 at the calibration range of 0.001-0.05 mg/kg. For recovery test, Atractylodes macrocephala Koidzumi or Achyranthes japonica Nakai was treated with standard solutions at MLOQ and 10MLOQ levels. Recovery rates were in the range of 88.1-109.1% with <5.5% coefficient of variation. This established analytical method was fully validated. Based on these results, it can contribute to improving the safety of residual pesticides in Atractylodes macrocephala Koidzumi and Achyranthes japonica Nakai.

• Korean Journal Plant Pathology
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• v.3 no.1
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• pp.17-19
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• 1987

• Korean Journal of Environmental Agriculture
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• v.41 no.2
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• pp.108-114
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• 2022

BACKGROUND: This study was performed to determine residual characteristics of soil-treated metalaxyl-M and dinotefuran in crown daisy and to evaluate the risks from intake of the residual pesticides in the crop. METHODS AND RESULTS: The pesticide granules were treated in soil on two levels, and the plants samples were collected 51 days after seeding. The analytes were extracted and partitioned using the QuEChERS extraction packet (MgSO₄ 4 g, NaCl 1 g). The quantitative methods for metalaxyl-M and dinotefuran were validated in linearity, accuracy, and precision. Risk assessments of the pesticides were performed using Korea national nutrition statistics 2019. CONCLUSION(S): The residual concentrations of metalaxyl-M in crown daisy were 0.09-0.10 mg/kg (for the treatment at 6 kg/10 a) and 0.17-0.19 mg/kg (12 kg/10 a), respectively. The residual concentrations of dinotefuran in the crop were 0.53-0.75 mg/kg (3 kg/10 a) and 1.17-1.26 mg/kg (6 kg/10 a). The amounts of pesticides were less than MRL (Maximum Residue Limits) according to the Korean MFDS (Ministry of Food and Drug Safety). The HI (Hazard Index) of metalaxyl-M and dinotefuran for consumers was 0.0075% and 0.2250%, respectively. For females in the age between 50-64, the major consumer group, the HIs of the pesticides were <3%. Considering the consumption of crown daisy, they are not considered to be of toxicological concern.

• The Plant Pathology Journal
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• v.25 no.4
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• pp.317-321
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• 2009

Sensitivity to the new carboxylic acid amide fungicide, mandipropamid, of Phytophthora capsici causing pepper Phytophthora blight was determined on 187 isolates collected in Korea over 3 years, from 2005 to 2007. All isolates were sensitive to mandipropamid, with $EC_{30}$ values for growth of mycelia ranging from 0.001 to $0.037\;{\mu}g/ml$. Among the isolates, 147 (79.0%) isolates were sensitive to metalaxyl, whereas others were resistant to this fungicide. Mandipropamid had the same effect on mycelium growth of both metalaxyl-sensitive and metalaxyl-resistant isolates, indicating an absence of cross-resistance between these two fungicides. Comparison of the sensitivities of P. capsici isolates showed a positive correlation between sensitivity to mandipropamid and dimethomorph ($r^2$=0.8533). The results of this study indicate that there is no evidence for development of resistance to mandipropamid in this population of P. capsici isolates collected in Korea.

• Korean Journal of Environmental Agriculture
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• v.17 no.3
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• pp.220-226
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• 1998

The effects of metalaxyl(granule), carbofuran(granule) and simazine(water soluble powder) on the soil microflora were conducted at field soil between Iksan and Chonju province. Pesticides were divided into 0.5, 1, 1.5 and 2.0 times of normal of field, respectively. The number of fluorescent Pseudomonas was ranged from $10^3$ to $10^6/g$ in both field soil treated with cabofuran. Pseudomonas concentration of Chonju field soil slowly increased and approached the maximum level at 56 day after treatment(DAT). It showed the higher at 14DAT than other DAT in Iksan field soil treated with metalaxyl or simazine, whereas it increased again at 112 DAT in metalaxyl treatment. Cabofuran treatment of both field soil showed maximum Pseudomonas number at 28 DAT compared to that of other treatments. In Chonju field soil, those Pseudomonads of metalaxyl and simazine treatment increased the highest level at 7 DAT. Simazine treatment decreased it's number from the beginning of experiment. In both soil, metalaxyl treatment decrease the general fungi number at 7 DAT, but increase at 14 and 56 DAT in Iksan field soil. However it increased at 56 DAT in Chonju field soil. Cabofuran treatment of Iksan field soil tended to decrease general fungi number at 28 DAT, but was ranged from 1.0 to $8.6{\times}104/g$ for the rest of experimental period. It started to increase at 56 DAT simazine treatment of Iksan. General bacterial concentration both soil treated with cabofuran was belong to $26.6{\sim}29.6{\times}106$. It was the highest at 56 DAT, but was not significantly different. General actinomyces number was highly increased at 7 and 112 DAT compared to that of other DAT. Pseudomonas putida or P. fluorescens from both field soil was separated and identified 10 to 30 of all 104 Pseudomonas, respectively. All isolated microorganisms showed chemical resistance of 100ppm metalaxyl, cabofuran and simazine treatment.

• The Korean Journal of Pesticide Science
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• v.6 no.4
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• pp.287-292
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• 2002

To establish effective and safe control method against Phytophthora root rot caused by Phytophthora capsici on tomato in hydroponic culture, three pesticides, oxadixyl copper hydroxide 8% WP, metalaxyl copper oxychloride 15% WP, and dimethomorph. dithianon 38% WP at 4 concentration levels were tested on potato dextrose agar medium inoculated with Phytophthora capsici. All pesticides inhibited mycelial growth, but two pesticides of them, metalaxyl copper oxychloride WP and dimethomorph. dithianon WP, were selected as effective pesticides for the efficacy test in a hydroponic culture. Forty days after transplanting of tomato seedlings, 4 ml of sporangia of P. capsici (about 25 sporangi/ml) per plot was inoculated around tomato plant root, and then 5 days after inoculation, the pesticides diluted at 5,000 times were drenched 1, 2 or 3 times per plot on the culture cube at 15 days interval. Fifteen days after drenching, tomato fruits and hydroponic culture solution were sampled for the analysis of pesticide residues. Dimethomorph was detected 0.001 and 0.003 mg/kg in tomato of the plots sprayed 2 and 3 times with dimethomorph dithianon WP of which detection levels were far below compared with 1.0 mg/kg of the Korean MRL of dimethomorph on tomato. Incidences of Phytophthora root rot were $30.5{\sim}50%$ in the plots drenched at 1 or 2 times with metalaxyl.copper oxychloride WP, and $16.7{\sim}25%$ in the plots treated with dimethomorph dithianon WP. However, there was no incidence of Phytophthora root rot in the plots treated at 3 times with both of pesticides, showing no phytotoxic effect. Based on the results, the drenching of these pesticides on the culture cube could be recommended as a very safe and effective control method for Phytophthora root rot in tomato.

• Journal of Life Science
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• v.11 no.6
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• pp.603-611
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• 2001

Phytolalexins are produced in plants affected by various environmental factors such as fungal infection treatment with many chemicals and irradiation by ultraviolet light. When pepper and tobacco bel suspension cultures were grown on a basal MS medium supplemented with 2,4-D(1mg/$\ell$, benzyl adenine(0.001 mg/$\ell$) and 100$\mu$ M jasmonic acid, the production of capsidiol was observed. The total of compound found in pepper plant were around seventy and thirty of them were located intissue-specific manner. 1-propanethiol, $\alpha$-D-xylofuranoside, phenol, hexadecanonic acid ethyl tridecanoate, phytol, linoleic acid and capsidiol are those which have change the production level by treatments, such as the inoculation of Phytophthora capsici Leonian, the metalaxyl treatment and the UV-B irradiation, respectively. The content of capsidiol on inoculation of P. capsici with metalxyl suspension in soil were higher than those of P.capsici without metalaxyl. When the soil dernch of metalaxyl treatment (1$\mu\textrm{g}$/${mu}ell$)was delayed after inoculation, the content of capsidiol were higher than that of before. Irrradiated UB-B the production on capsidiol was identified only at leaf, and contents were the highest for 24 hrs incubation after 20 minutes irradiation.