• Journal of Food Hygiene and Safety
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• v.34 no.1
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• pp.22-29
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• 2019

Validamycin A is an aminoglycoside fungicide produced by Streptomyces hygroscopicus that inhibits trehalase. The purpose of this study was to develop a method for detecting validamycin A in agricultural samples to establish MRL values for use in Korea. The validamycin A residues in samples were extracted using methanol/water (50/50, v/v) and purified with a hydrophilic-lipophilic balance (HLB) cartridges. The analyte was quantified and confirmed by liquid chromatograph-tandem mass spectrometer (LC-MS/MS) in positive ion mode using multiple reaction monitoring (MRM). Matrix-matched calibration curves were linear over the calibration ranges (0.005~0.5 ng) into a blank extract with $R^2$ > 0.99. The limits of detection and quantification were 0.005 and 0.01 mg/kg, respectively. For validation validamycin A, recovery studies were carried out three different concentration levels (LOQ, $LOQ{\times}10$, $LOQ{\times}50$, n = 5) with five replicates at each level. The average recovery range was from 72.5~118.3%, with relative standard deviation (RSD) less than 10.3%. All values were consistent with the criteria ranges requested in the Codex guidelines (CAC/GL 40-1993, 2003) and the NIFDS (National Institute of Food and Drug Safety) guideline (2016). Therefore, the proposed analytical method is accurate, effective and sensitive for validamycin A determination in agricultural commodities.

• The Korean Journal of Pesticide Science
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• v.17 no.3
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• pp.185-192
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• 2013

This study was performed to evaluate the spray toxicity and leaf residual toxicity of 52 kinds of insecticides registered for strawberry against adult honeybee Apis mellifera. According to the IOBC standard, the acute toxicity by spraying showed below 30% was classified as non-toxic. Among tested insecticides, 32 insecticides (flonicamid, lufenuron, novaluron, three kinds of acetamiprid, thiacloprid, milbemectin, acequinocyl, TBI-1, two kinds of chlorfenapyr, chlorfluazuron, cyenopyrafen, cyfumetofen, etoxazole, fenpyroximate, flubendiamide, flufenoxuron, hexythiazox, metaflumizone, two kinds of methoxyfenozide, DBB-2032, pyridalyl, spiromesifen, tebufenpyrad, teflubenzuron, acetamiprid + methoxyfenozide, acrinathrin + spiromesifen, bifenazate + spiromesifen, cyenopyrafen + flufenoxuron) did not show any toxic effect, it is thought to be safe. And the others (20 insecticides) showed higher toxicity to honeybee. Insecticides which showed acute toxicity higher than 90% was selected and tested the residual toxicity. All insecticides except emamectin benzoate EC, and indoxacarb SC showed 100% mortality at one day after treatment (DAT). However, the toxicities of emamectin benzoate, indoxacarb SC, and abamectin did not show until 3, 7, 14 DAT, respectively. Nine insecticides such as indoxacarb WP, thiamethoxam WG, abamectin + chlorantraniliprole SC, acetamiprid + etofenprox WP, acetamiprid + indoxacarb WP, bifenthrin + clothianidin SC, bifenthrin + imidacloprid WP, bifenazate + pyridaben SC, chlorfenapyr + clothianidin SC showed over 90% residual toxicity until 31 Day. In pouring treatment, thiamethoxam WG showed 76.9% mortality at 28 DAT and 50.0% mortality at 31 DAT. After 35 days, thiamethoxam WG showed no effect to honeybee. Bifenthrin + clothianidin SC and tefluthrin + thiamethoxam GR showed 57.1 and 80.0% mortality at 24 DAT, respectively. In spraying treatment, thiamethoxam WG and bifenthrin+clothianidin SC showed very high residual toxicity with 100% mortality in thirty-five DAT. After spraying treatment with thiamethoxam WG, bifenthrin+clothianidin SC, bifenthrin + imidacloprid WP, thiamethoxam WG showed 100% residual toxicity until 21 DAT and there was no activity after 28 DAT. Bifenthrin+clothianidin SC and bifenthrin+imidacloprid WP showed very high residual toxicity until 49 DAT.

• The Korean Journal of Pesticide Science
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• v.17 no.4
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• pp.264-270
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• 2013

Imidacloprid is a systemic insecticide which act as an insect neurotoxin. It used for control of pest such as aphids and other sucking insects in fruits and vegetables. Systemic pesticides move inside a crop following absorption by the plant, and these were converted into a variety of metabolites. Sometimes these metabolites make a problem about safety of agricultural products. So a simultaneous determination method of pesticide and its metabolites is needed, to monitor their presence in agricultural product and study on the fate of pesticide in a plant. This study's aim is to investigate simultaneous analysis method of imidacloprid and its metabolites, imidacloprid guanidine, imidacloprid olefin, imidacloprid urea, and 6-chloronicotinic acid in red pepper using QuEChERS method and LC-MS/MS systems. QuEChERS method was modifed beacuase $MgSO_4$ salts decreased the recoveries of 6-chloronicotinic acid in extraction procedure. Imidacloprid and its metabolites were extracted by acetonitrile with 1% glacial acetic acid and the extracts were purified through QuEChERS with primary secondary amine (PSA) and $C_{18}$ and analyzed with LC-MS/MS in ESI positive mode. Standard calibration curves were made by matrix matched standards and their correlation coefficients were higher than 0.999. Recovery studies were carried out on spiked pepper blank sample at four concentration levels (0.01, 0.04 and 0.1, 0.4 mg/kg). The average recoveries of imidacloprid and its metabolites were in the range of 70~120% with < 20% RSD. This result indicated that the method using QuEChERS and LC-MS/MS was suitable for the simultaneous determination of imidacloprid and its metabolites in red pepper.

• Korean Journal of Environmental Agriculture
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• v.13 no.3
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• pp.279-287
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• 1994

To develop mixed pesticides of herbicide and topdressing fertilizer for paddy rice, twelve mixtures were formulated with combination of urea coated with different level of acrylic acid wax(AAW) and four herbicides, which were thiobencarb, pretilachlor, mefenacet + bensulfuron-methyl and mefenacet + bensulfuron-methyl + dymron, and effects of the mixtures for weed control, phytotoxicity and rice tillering were investigated in the laboratory and the field experiments. Release rates of active ingredient of herbicides in the distilled water were over 90% during 24 hours same as that of the reference herbicides. The release rates of nitrogen showed different patterns according to coated level of granular urea with acrylic acid wax. Optimum release rate of nitrogen as $NH_4-N$ was obtained by 5.5% AAW coating on urea for thiobencarb or pretilachlor mixture, and by 4.0% AAW coating on urea for mefenacet + bensulfuron-methyl or mefenacet + bensulfuron-methyl + dymron mixture. The pesticide active ingredients of the mixtures were stable, which showed $3.7{\sim}8.0%$ of degradation rate after 90 days of storage under $50^{\circ}C$. Effects on weed control of mixtures were acceptable for both annual and perennial weeds, while ACRI-M9213 mixture showed considerable phytotoxicity at double dose of standard. When treated the mixed pesticides to paddy rice, rice growth status including culm length, ear length, panicle number and polished rice yield exhibited no significant differences compared with the conventional treatment.

• Microbiology and Biotechnology Letters
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• v.46 no.3
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• pp.253-260
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• 2018

Beneficial microorganisms are widely used in the forestry, livestock, and, in particular, agricultural sectors to control soilborne diseases and promote plant growth. However, the industrial utilization of these microorganisms is very limited, mainly due to uncertainty concerning their ability to colonize and persist in soil. In this study, the survival of beneficial microorganisms in field soil microcosms was investigated for 13 days using quantitative PCR with B. subtilis group-specific primers. Bacterial community dynamics of the treated soils were analyzed using 16S ribosomal RNA (rRNA) gene amplicon sequencing on the Illumina MiSeq platform. The average 16S rRNA gene copy number per g dry soil of Bacillus spp. was $4.37{\times}10^6$ after treatment, which was 1,000 times higher than that of the control. The gene copy number was generally maintained for a week and was reduced thereafter, but remained 100 times higher than that of the control. Bacterial community analysis indicated that Acidobacteria ($26.3{\pm}0.9%$), Proteobacteria ($24.2{\pm}0.5%$), Chloroflexi ($11.1{\pm}0.4%$), and Actinobacteria ($9.7{\pm}2.5%$) were abundant phyla in both treated and non-treated soils. In the treated soils, the relative abundance of Actinobacteria was lower, whereas those of Bacteroidetes and Firmicutes were higher compared to the control. Differences in total relative abundances of operational taxonomic units belonging to several genera were observed between the treated and non-treated soils, suggesting that inoculation of soil with the Bacillus strains influenced the relative abundances of certain groups of bacteria and, therefore, the dynamics of resident bacterial communities. These changes in resident soil bacterial communities in response to inoculation of soil with beneficial Bacillus spp. provide important information for the use of beneficial microorganisms in soil for sustainable agriculture.

• The Korean Journal of Pesticide Science
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• v.20 no.3
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• pp.271-279
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• 2016

To evaluate exposure characteristics of the insecticide imidacloprid to apple orchard workers during treatment on orchard fields and evaluate its potential risk using a whole body dosimetry (WBD) method, 1,000-time diluted acephate+imidacloprid 25(20+5)% solutions were sprayed on 10 apple orchard fields in Cheongju with a speed sprayer at a rate of 3,000 L/ha/person, after put on clothes such as inner/outer clothes, personal air pump with a IOM sampler, nitrile glove and mask. Exposure test included mixing, loading and application steps. The test pesticide imidacloprid residues in the collected samples were analyzed with a HPLC-DAD. Recoveries ranged from 81.5 to 108.6% for analytical method validation and from 73.8 to 86.7% for field recovery. Total exposed amounts to mixer/loader and applicator were found to be 0.0014-0.0279% of total applied active ingredient of imidacloprid. Glove exposure of both mixer/loader and applicator was higher than the other parts. Margins of safety of mixer/loader and applicator were calculated to be 97-355 and 46-196, respectively, indicating that exposure risk of imidacloprid to apple orchard workers by spraying with a speed sprayer was very low.

• Korean Journal of Weed Science
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• v.32 no.2
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• pp.98-106
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• 2012

This research has been carried out to find out the highest effect on insecticidal, fungicidal and herbicidal activities in leaves, stem and tuber extracts of yacon (Smallanthus sonchifolius) and extraction methods such as water, boiling water and methanol. Characteristics of potential herbicidal components among extraction methods were investigated by solvent fractions such as hexane, chloroform, ethyl acetate, butanol, and water. Generally, methanol extract was the best on inhibition of germination rate, plant height, and root length in cucumber and barley. On the other hand, the inhibition effect on growth in cucumber and barley was the best in tuber among plant parts of yacon. Inhibition of germination rate, plant height, and root length in cucumber and barley in solvent fractions was the best in water fraction, but there were no differences in other fractions. Digitaria sanguinalis L. and Solanum nigrum L. by 5 and 10% extractions of yacon tuber were controlled by more than 70~80% and 95~100%, respectively. However, there was no inhibition effect on foliar treatment in cucumber and barley as affected by 5 and 10% extractions of yacon tuber. Mortality of green peach aphid (Myzus persicae Sulzer) was 50% at 3 days after treatment of 5% extracts of yacon leaves. Mortality of brown plant hopper (Nilaparvata lugens Stal) was only 24% in 5% extracts of stems and leaves with midrib, but was 57% in 5% extracts of leaves without midrib. There was no fungicidal effect on anthracnose (Colletotrichum truncatum), wilt disease (Fusarium oxysporum), verticillium wilt (Verticillium dahliae), bacterial blight (Xanthomonus oryzae) in 5% extracts of yacon leaves.

• The Korean Journal of Ecology
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• v.24 no.3
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• pp.157-168
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• 2001

Herbicides have been used to control weeds for decades. If detoxification upon exposure to herbicides requires considerable amounts of energy, it could affect the pattern of resource allocation to growth and reproduction of crops. We examined the effects of three levels of a herbicide (Control, Low, and High) on germination, growth and reproductive characters of Glycine max treated twice, i.e., before and after seed germination. Since flowering time of G. max was separated into two groups, flowering time was also considered as a variable in this study. The rate of seed germination tended to be higher at the low level of herbicide compared to other levels. Chlorosis and shape variation of leaves were apparent after the second herbicide treatment, but completely disappeared after six weeks of treatment. The herbicide effects on growth characters were somewhat different between early and late flowering plants, but plants treated with both low and high levels of herbicide reduced their growth compared to those in the control group regardless of flowering time. Plants at the high level of herbicide exhibited the highest growth rate later in the season, suggesting that plants compensated to some extent for reduced growth. However, growth reduction among plants at the high level of herbicide was persistent until the end of growing season. Among plants flowered late in the season, plants in the control level bore a higher number of nodules per plant than those in other levels; such a pattern did not exist among plants flowered early in the season. Plants treated with low and high levels of herbicide produced a lower number of flowers than those in the control. Thus, the herbicide examined affected not only the growth and reproductive characters of non-target crops but also the development and growth of root nodules.

• Journal of Food Hygiene and Safety
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• v.32 no.4
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• pp.298-305
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• 2017

Benzovindiflupyr is a new pyrazole carboxamide fungicide that inhibits succinate dehydrogenase of mitochondrial respiratory chain. This study was carried out to develop an analytical method for the determination of benzovindiflupyr residues in agricultural commodities using LC-MS/MS. The benzovindiflupyr residues in samples were extracted by using acetonitrile, partitioned with dichloromethane, and then purified with silica solid phase extraction (SPE) cartridge. Correlation coefficient ($r^2$) of benzovindiflupyr standard solution was 0.99 over the calibration ranges ($0.001{\sim}0.5{\mu}g/mL$). Recovery tests were conducted on 5 representative agricultural commodities (mandarin, green pepper, potato, soybean, and hulled rice) to validate the analytical method. The recoveries ranged from 79.3% to 110.0% and then relative standard deviation (RSD) was less than 9.1%. Also the limit of detection (LOD) and limit of quantification (LOQ) were 0.0005 and 0.005 mg/kg, respectively. The recoveries of interlaboratory validation ranged from 83.4% to 117.3% and the coefficient of variation (CV) was 9.0%. All results were followed with Codex guideline (CAC/GL 40) and Ministry of Food and Safety guideline (MFDS, 2016). The proposed new analytical method proved to be accurate, effective, and sensitive for benzovindiflupyr determination and would be used as an official analytical method.

• Korean journal of applied entomology
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• v.51 no.4
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• pp.431-438
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• 2012

The developmental time of the nymphs of Myzus persicae was studied in the laboratory (six constant temperatures from 15 to $30^{\circ}C$ with 50~60% RH, and a photoperiod of 14L:10D) and in a green-pepper plastic house. Mortality of M. persicae in laboratory was high in the first(6.7~13.3%) and second instar nymphs(6.7%) at low temperatures and high in the third (17.8%) and fourth instar nymphs(17.8%) at high temperatures. Mortality was 66.7% at $33^{\circ}C$ in laboratory and $26.7^{\circ}C$ in plastic house. The total developmental time was the longest at $14.6^{\circ}C$ (14.4 days) and shortest at $26.7^{\circ}C$ (6.0 days) in plastic house. The lower threshold temperature of the total nymphal stage was $3.0^{\circ}C$ in laboratory. The thermal constant required for nymphal stage was 111.1DD. The relationship between developmental rate and temperature was fitted nonlinear model by Logan-6 which has the lowest value on Akaike information criterion (AIC) and Bayesian information criterion (BIC). The distribution of completion of each developmental stage was well described by the 3-parameter Weibull function ($r^2=0.95{\sim}0.97$). This model accurately described the predicted and observed occurrences. Thus the model is considered to be good for use in predicting the optimal spray time for Myzus persicae.