Chinese cabbage has long been consumed as a staple food by the Koreans in various forms of fresh, salted, or fermented as kimchi. To fulfill the off-season demand for this crop, it has become a common practice to be cultivated under greenhouse conditions. Since pesticide residues in/on leafy vegetables have strongly concerned with food safety in the Korean society, the changes of lufenuron residues, in/on Chinese cabbage applied by foliar spraying under greenhouse conditions was investigated. Lufenuron 5% emulsifiable concentrate (EC) was sprayed with diluted solution of recommended and double doses to the crop. The shoots of the cabbage were harvested immediately after spraying, and sequentially the harvests were conveyed to analyze the residual amounts. The deposited level of the analyte in/on Chinese cabbage under greenhouse conditions seemed to be difficult to produce the crop with 0.2 ppm of maximum residue limit (MRL) of the Korea Food and Drug Administration (KFDA).
The principal goal of this work was to develop an efficient method for the simultaneous determination of four pyrethroid (PYR) insecticides, cyfluthrin, cyhalothrin, cypermethrin, and deltamethrin, in porcine muscle and pasteurized milk using liquid-liquid extraction (LLE). Sample extraction was carried out with and without additional column cleanup procedures, and the final determination was made using GC with electron-capture detector (ECD). The pesticide identity was confirmed using GC-MS in the SIM mode. Since there were minor differences between the extraction procedures, extraction without the additional cleanup procedure was used throughout the work. The method was validated by fortifying blank samples with half, two, and four times the maximum residue limit (MRL) of each PYR. The average recoveries (n = 6) ranged from 83.5 to 99.2% and 82.9 to 109% in porcine muscle and pasteurized milk, respectively. The repeatability of measurements expressed as RSDs, was in the range of 1.7-11.9 and 1.5-10.3% in porcine muscle and pasteurized milk, respectively. The LODs ranged from 3.3 to 9 and 3 to 8.1 ppm, whereas the LOQs ranged from 10 to 27.4 and 9 to 24.6 ppm, in porcine muscle and pasteurized milk, respectively. The applicability of the method was demonstrated by analyzing real samples collected from major cities in the Republic of Korea. No residues of the selected pesticides were detected in any of the samples.
The evaluation of a total of 122 blast (Pyricularia oryzae Cavara) isolates collected from the Tonle Sap and Mekong river regions of Cambodia revealed wide variation. Using a new designation system, the blast isolates were categorized into 92 races based on the reaction patterns of rice (Oryza sativa L.) differential varieties (DVs) harboring 23 resistance genes and of 1 susceptible cultivar, Lijiangxintuanheigu (LTH). Cluster analysis was used to classify the blast isolates into 3 groups -I, IIa, and IIb -using data from these reaction patterns of the DVs and LTH. We used the classifications established under the new designation system, alongside cluster analysis and the geographical distribution of blast isolates, to investigate the diversity and differentiation of blast races in the Tonle Sap and Mekong river regions. The distributions of the blast races differed between the 2 regions, although blast isolates of group IIa were distributed commonly in both regions and groups I and IIb occurred at higher frequencies in the Tonle Sap region rather than the Mekong region. The blast isolates in groups I and IIb were also less diverse than those in group IIa. Accordingly, Group II blast isolates overall were distributed in both regions with high diversity, but some modified blast isolates were additionally distributed in the Tonle Sap region. We also investigated the pathogenicities of blast isolates from wild rice (Oryza rufipogon Griff) weeds neighboring the cultivated rice, and discuss the relationship between these isolates and those from cultivated rice.
The white-backed planthopper, Sogatella furcifera (Horváth) (Hemiptera: Delphacidae), is a serious pest of rice in Asia. However, little is known regarding the migration of this pest insect from the Greater Mekong Subregion (GMS) including Cambodia, Laos, Myanmar (Burma), Thailand, and Vietnam, into China’s Yunnan Province. To determine the migration patterns of S. furcifera in the GMS and putative secondary immigration inside China’s Yunnan Province, we investigated the population genetic diversity, genetic structure, and gene flow of 42 S. furcifera populations across the six countries in the GMS by intensive sampling using mitochondrial genes. Our study revealed the potential emigration of S. furcifera from the GMS consists primarily of three major sources: 1) the S. furcifera from Laos and Vietnam migrate into south and southeast Yunnan, where they proceed to further migrate into northeast and central Yunnan; 2) the S. furcifera from Myanmar migrate into west Yunnan, and/or central Yunnan, and/or northeast Yunnan; 3) the S. furcifera from Cambodia migrate into southwest Yunnan, where the populations can migrate further into central Yunnan. The new data will not only be helpful in predicting population dynamics of the planthopper, but will also aid in regional control programs for this economically important pest insect.
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