• Korean journal of applied entomology
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• v.34 no.4
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• pp.360-367
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• 1995

The relative toxicity of abamectin was assessed to the predatory mite Amblyseius womersleyi Schicha and to dicofol-resistant and -susceptible twospotted spider mite (TSM) Tetranychus urticae Koch in the laboratory. Abamectin was much les toxic to the predator than to the spider mite. At 0.12 and 0.6 ppm, all TSM adult females of the tow strains were killed within 48 h after dipping n the solutions. The lower concentrations (0.06 and 0.012 ppm) killed more than 77% of TSM female adults of the two strains at 120 h after treatment. However, abmectin did not significantly affect the survival and mobility of A. womersleyi female adults at a concentration of 0.12 ppm but the mortality was slightly increased up to 20~23% at 0.6 and 6 ppm. Abamectin did not significantly affect hatchability of one-day old TSM eggs at 0.06~0.6 ppm. The Four-day old eggs were much more susceptible to abamectin than one-day old eggs were. Within 0.006-6 ppm, abamectin did not affect the hatchability of A. womersleyi eggs and the development of resulting immature predators. When the predator female adults were dipped in 0.6 and 0.12 ppm solution, their reproduction was not affected, but at 6 ppm it was decreased by 35%. However, the reproduction of TSM reduced significantly at concentrations between 0.006 and 0.6 ppm. The differential toxicity of abamectin between TSM and the predator could be of practical importance in managing spider mite populations in the field. Abamectin at selective sublethal concentrations (i.e., 0.012~0.06 ppm) could be of value in adjusting predator/prey ratios in integrated management of spider mites.

• Korean Journal of Environmental Biology
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• v.35 no.4
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• pp.427-436
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• 2017

A fixed-precision-level sampling plan was developed to establish control of the two-spotted spider mite, Tetranychus urticae, in two strawberry greenhouses (conventional plot, natural enemy plot). T. urticae was sampled by taking a three-leaflet leaf (1 stalk) from each plant (3 three-leaflet leaves) from each sampling position. Each leaflet was divided into three different units (1-leaflet, 2-leaflet, and 3-leaflet units) to compare relative net precision (RNP) values for selection of the appropriate sampling unit. The relative net precision values indicated that a 1-leaflet unit was more precise and cost-efficient than other units. The spatial distribution analysis was performed using Taylor's power law (TPL). Homogeneity of the TPL parameters in each greenhouse was evaluated by using the analysis of covariance (ANCOVA). A fixed-precision-level sequential sampling plan was developed using the parameters of TPL generated from the combined data of the conventional plot and natural enemy plot in a 1-leaflet sampling unit. Sequential classification sampling plans were also developed using the action threshold of 3 and 10 mites for pooled data. Using the results obtained in the independent data, simulated validation of the developed sampling plan by Resampling validation for sampling plan (RVSP) indicated a reasonable level of precision.

• The Korean Journal of Pesticide Science
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• v.14 no.4
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• pp.319-325
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• 2010

To understand the influences of the substituents ($R_1{\sim}R_4$) on insecticidal activity of N'-phenyl-N-methylformamidine analogues (1~22) against two spotted spider mite (Tetranychus urticae), comparative molecular field analysis (CoMFA) model and comparative molecular similarity indices analysis (CoMSIA) model as three dimensional quantitative structure-activity relationships (3D-QSARs) model were derived and discussed quantitatively. From the results, the correlativity and predictability ($r^2{_{cv.}}=0.575$ and $r^2{_{ncv.}}=0.945$) of the CoMFA 1 model were higher than those of the rest models. The the CoMFA 1 and CoMSIA 1 model with the sensitivity of the perturbation and the prediction produced ($d_q{^{2'}}/dr^2{_{yy}}=1.071{\sim}1.146$ & $q^2=0.545{\sim}0.626$) by a progressive scrambling analysis were not dependent on chance correlation. The insecticidal activities from the optimized CoMFA 1 model were depend upon the steric field (62.5%), electrostatic field (28.9%), and hydrophobic field (8.6%) of N'-phenyl-N-methylformamidine analogues. Therefore, the inhibitory activities with optimized CoMFA 1 model were dependent upon steric factor. From the contour maps of the optimized models, it is predicted that the structural distinctions that contribute to the insecticidal activity will be able to applied new potent insecticides design.

• Korean journal of applied entomology
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• v.25 no.3 s.68
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• pp.133-138
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• 1986

This study was conducted to compare the methods of slide dip and leaf dip techniques in the resistant level determination of spider mites to acaricides used; .and to investigate resistant levels of two-spotted spider mite, Tetranychus urticae Koch to benzomate, dicofol and cyhexatin in Honam region of Korea. Comparisons of the resistant strains and susceptible strain based on $LC_{50}$ values were summarized. Using the slide dip and leaf dip techniques with benzomate acaricide, the Keumchun strain of T. urticae showed 75-and 69-fold resistant levels, respectively, as compared with the Kwangju susceptible strain, but the Hackyo strain was 38-and 35-fold resistant levels, respectively. There was no significant difference (P>0.05) between the slide dip and leaf dip methods. With dicofol acaricide, resistant levels of the Keumchun strain of T. urticae were 71 times by using the slide dip and 74 times by using the leaf dip as resistant as the Kwangju susceptible strain while the Hackyo strain was 24 times by the former method and 23 times by the later method. There was also no significant difference (P>0.05) between both the methods. The slide dip technique is more recommendable than the leaf dip technique for determination of degree of chemical resistance to the spider mites with accuracy and less variation of the results. Using the slide dip method with cyhexatin, the Bia, Keumchun and Hackyo strains of T. urticae were 19-, 18- and 9-fold resistant levels, respectively, over the Kwangju susceptible strain.

• The Korean Journal of Pesticide Science
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• v.4 no.3
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• pp.27-33
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• 2000

N-Dimethoxyphosphinothionyl carbofuran, PSC, has a high insecticidal activity and low mammalian toxicity. Ten N-phosphinothionyl carbofuran derivatives were synthesized and their insecticidal activities were determined against brown plant hopper (Nilaparvata lugens), green peach aphid (Myzus persicae), diamondback moth (Plutella xylostella), and two-spotted spider mite (Tetranychus urticae). Green peach aphid, diamondback mea and brown plant hopper were controlled over 90% by application of 125 ppm, 125 ppm, and 63 ppm, respectively, of carbosulfan. Two hundred and fifty ppm of newly synthesized compounds could control most of brown plant hopper and diamondback moth. Especially, insecticidal activities of compound 10 against brown plant hopper, diamondback moth, and green peach aphid were similar to those of carbosulfan. Our results show that the newly synthesized derivatives of NV-phosphinothionyl carbofuran have a similar insecticidal activity to carbosulfan.

• Korean journal of applied entomology
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• v.53 no.4
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• pp.391-398
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• 2014

This study investigated inhibitory doses of electron beam and X-ray irradiation by comparing their effects on the development and reproduction of four insect pests (Myzus persicae, Tetranychus urticae, Liriomyza trifolii, and Frankliniella intonsa). When M. persicae nymphs were irradiated with 100 Gy of electron beam and 30 Gy of X-ray beam, offspring production by adults that developed from the treated nymphs was completely inhibited. When M. persicae adults were irradiated with 200 Gy of electron beam and 50 Gy of X-ray beam, emergence of the $F_1$ generation was inhibited. However, these two ionizing radiations did not affect adult longevity. When T. urticae eggs were irradiated with 150 Gy of electron beam and 50 Gy of X-ray beam, egg hatching was completely inhibited. When L. trifolii pupae were irradiated, the emergence rate decreased with increasing doses of X-ray irradiation. After F. intonsa adults were irradiated with 250 Gy of electron beam and 200 Gy of X-ray beam, egg hatching of the $F_1$ generation was completely suppressed.

• The Korean Journal of Pesticide Science
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• v.3 no.1
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• pp.20-28
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• 1999

Chloronicotinyl derivatives were synthesized by substitution of amino in 3-pyridylmethylamine with phosphite groups and their insecticidal and fungicidal activities were determined. At 500 ppm, compound 4 with methyl and butyl group in phosphonate and compound 5, 6, 7, and 8 with two butyl, 2,2,2-trifluorotehtyl, 2-ethylhexyl, phenyl, respectively, in phosphonate showed 90% insecticidal activities against brown plant-hopper (Nilaparvate lugens). These compounds showed, however, poor insecticidal activities against diamond-back moth (Plutella xylostella) and two-spotted spider mite (Tetranychus urticae) (<65%), suggesting that insecticidal activity of chloronicotinyl derivatives containing phosphorus moieties are species-dependent. Newly synthesized chloronicotinyl derivatives with halogen and/or heterocycle (compound $10{\sim}21$) did not show insecticidal activities. We also determined fungicidal activity of the synthesized chloronicotinyl derivatives against rice sheath blight (Pyricularia grisea), cucumber gray mold (Bortytis cinerea), tomato late blight (Phytophthora infestans), wheat leaf rust (Puccinia recondita), and barley powdery mildew (Erysiphe graminis). Compound 10 with butyl and 4-nitrophenyl in phosphonate at 10 ppm showed 85% fungicidal activity against rice blast, suggesting that chloronicotinyl derivatives containing phosphorus moieties could be developed as a fungicidal agent of a novel chemical structure.

• Research in Plant Disease
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• v.9 no.2
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• pp.99-103
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• 2003

Bioactivities of Korean ginkgo (Ginkgo biloba L.) extract were investigated against several fungi, general bacteria and insect pests. Crude methanolic extracts of different parts of Korean ginkgo showed different bioactivities depending on the target organisms. The methanolic extract showed in vitro antimicrobial activity at dose of 200 ug per paper disc. The extract of ginkgo stalk was some higher than seed coat and root. The extract also showed a remarkable in vivo antifungal activity against green mold (Trichoderma harzianum) on compost surface of spawn bags and in vivo insecticidal activity to Nilaparvata lugens, Plutella xylostella and Tetranychus urticae. This study suggests that Korean ginkgo extracts have a potential as a natural pesticide.

• Korean journal of applied entomology
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• v.51 no.1
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• pp.47-58
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• 2012

Effect of a new crop protectant 'Bt-Plus' on natural enemies was analyzed in this study. Tested natural enemies included two parasitic species of $Aphidius$ $colemani$ and $Eretmocerus$ $eremicus$, and four predatory species of $Harmonia$ $axyridis$, $Orius$ $laevigatus$, $Amblyseius$ $swirskii$, and $Phytoseiulus$ $persimilis$. 'Bt-Plus' was formulated by combination of three entomopathogenic bacteria ($Xenorhabdus$ $nematophila$ (Xn), $Photorhabdus$ $temperata$ subsp. $temperata$ (Ptt), $Bacillus$ $thuringiensis$ (Bt)) and bacterial metabolite (BM). All three types of 'Bt-Plus' showed significantly higher toxicities against fourth instar $Plutella$ $xylostella$ larvae than Bt single treatment. Two types of bacterial mixtures ('Xn+Bt' and 'Ptt+Bt') showed little toxicity to all natural enemies in both contact and oral feeding assays. However, 'BM+Bt' showed significant toxicities especially to two predatory mites of $A.$ $swirskii$ and $P.$ $persimilis$. The acaricidal effects of different bacterial metabolites were evaluated against two spotted spider mite, $Tetranychus$ $urticae$. All six BM chemicals showed significant acaricidal effects. The BM mixture used to prepare 'Bt-Plus' showed a high acaricidal activity with a median lethal concentration at 218.7 ppm (95% confidence interval: 163.2 - 262.3). These toxic effects of bacterial metabolites were also proved by cytotoxicity test against Sf9 cells. Especially, benzylideneacetone, which was used as a main ingredient of 'BM+Bt', showed high cytotoxicity at its low micromolar concentration.