• 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.

• Korean Journal of Agricultural Science
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• v.45 no.1
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• pp.38-42
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• 2018

Demand for tomatoes has been increasing every year as people desire more healthy food. In Korea, tomatoes are mainly grown in the Chungnam, Chunnam and Kyungnam provinces. Recently, reports of whitefly-transmitted viral diseases have increased due to newly emerging whitefly pressures caused by climate change in Korea. Specifically, in 2017, the main tomato growing areas, Buyeo and Nonsan in Chungnam, showed damage typical of viral infection; therefore, we investigated viral diseases in these areas. We collected samples with virus-like symptoms and found that not only whitefly transmitted Tomato yellow leaf curl virus (TYLCV) and Tomato chlorosis virus (ToCV) were detected but also Tomato mosaic virus (ToMV, for which no specific vector is known) and Tomato spotted wilt virus (TSWV, transmitted by thrips). The ToMV-infected samples were mostly co-infected with either TYLCV or ToCV. Mixed infections of different combinations of TYLCV, ToCV and ToMV were detected with the mixed infection of two whitefly-transmitted viruses (TYLCV and ToCV) causing the most severe symptoms. According to the CP sequence of each virus, the 100% identities were shown to be Mexico/ABG73017.1 (TYLCV), Greece/CDG34553.1 (ToCV), China/AKN79752 (TSWV), and Australia/NP078449.1 (ToMV). Based on the sequence data, we presumed that these tomato infecting viruses were transmitted through insects and seeds introduced from neighboring countries.

• Korean journal of applied entomology
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• v.49 no.3
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• pp.199-204
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• 2010

The seasonal fluctuation of the large 28-spotted lady beetle, Henosepilachna vigintioctomaculata (Motschulsky), was observed in potato fields of Gangneung region, Gangwondo Province. The effects of their leaf consumption over a 24 hour period and developmental periods by different temperatures were investigated, and then the developmental threshold (DT) and effective cumulative temperature (ET) of each stage were calculated. Various developmental stages of H. vigintioctomaculata were captured in the fields from May to September, with three peaks in late May, late June, and late August. Leaf consumption by larval stages increased with the development of instar. The 4th instar larvae consumed potato leaves much more than other stages. Egg hatchability and emergence rate of H. vigintioctomaculata were lower at $10^{\circ}C$ and $30^{\circ}C$, but higher at around $20{\sim}23^{\circ}C$. The developmental periods of each stage became shorter as temperature increased; 90 days at $10^{\circ}C$, 40 days at $20^{\circ}C$ and 25 days at $25^{\circ}C$. Base on developmental velocity to temperature, calculated DT and ET were $7.3^{\circ}C$ and 83.

• Korean Journal Plant Pathology
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• v.11 no.4
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• pp.344-347
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• 1995

Factors affecting on the ascospore release of Mycosphaerella nawae, the causal organism of persimmon leaf casting disease, were investigated. The ascospore release of the pathogen occurred following the precipitation of rain. The ascospore release started from the beginning of raining, reached maximum at 2 hours after the precipitation of rain, and then decreased abruptly. When the inoculum source (a file of infected leaves) was submerged in water to imitate raining conditions, 92.5% of the total ascospores were released within 1 hour after submerging, 5.8% were after 2 hours, 1.4% were after 4 hours, 0.1% were after 8 hours, and none detected after 10 hours. The inoculum source overwintered in the field released ascospores much more and earlier than the inoculum source kept in the greenhouse. The first ascospore release was about 10 days earlier, and the amount of the total liberated spores was 3∼4 times higher in the field inoculum source than the greenhouse nioculum source. The early defoliated leaves (in early October) in the previous year produced ascospores twice more than the late defoliated leaves (in early November) produced.

• Mycobiology
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• v.29 no.2
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• pp.107-109
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• 2001

Anthracnose symptoms severely occurred up to 50% on leaves of English ivy growing in greenhouses in Cheongwon area of Korea during disease survey in April, 2000. The symptoms developed as concentric spots with dot-like acervuli on leaves of the plant. A total of 24 isolates of Colletotrichum sp. were obtained from the spotted lesions and identified as Colletotrichum trichellum based on the morphological and cultural characteristics. Leaf spots similar to the original anthracnose symptoms were induced on the host leaves by artificial inoculation with the isolates of the fungus. This is the first record of C. trichellum causing anthracnose of English ivy in Korea.

• Mycobiology
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• v.30 no.1
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• pp.57-59
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• 2002

Anthracnose symptoms severely occurred up to 100% on leaves of May lily grown in four locations in Korea during a disease survey in 2001. The symptoms appeared as circular to irregular spots with brown to dark brown discoloration on leaves of the plant, and severely infected leaves blighted. A total of 35 isolates of Colletotrichum sp. was obtained from the spotted lesions and identified as Colletotrichum liliacearum based on the morphological and cultural characteristics. Leaf spots similar to the original anthracnose symptoms were induced on the host leaves by artificial inoculation with the isolates of the fungus. This is the first report that C. liliacearum causes anthracnose of May lily.

• Korean journal of applied entomology
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• v.34 no.1
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• pp.40-45
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• 1995

Eight field-collected populations of the two-spotted spider mites, Tetranychus urticae (Koch) from apple orchards of different geographical areas were tested for resistance to seven acaricides by leaf disk method in comparison with a susceptible strain. Marked regional variations of susceptibility were observed. Only low to moderate resistance to azocyclotin, fenpropathrin, propargite, and abamectin was obtained. However, high resistance to dicofol, fenpyroxymate, and pyridaen by eight field-collected populations was produced. Resistance to dicofol and fenpyroxymate was widespread. All of the strains tested were susceptible to one or more o the acaricides used. These results indicate that careful selection of the chemical used against any population of the two-spotted spider mite might result in satisfactory control.

• Journal of Bio-Environment Control
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• v.31 no.1
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• pp.43-51
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• 2022

This study was conducted to investigate the effect of ventilation at high temperature on the control of powdery mildew, silverleaf whitefly two-spotted spider mite occurred at Korean melon cultivation greenhouse, and on leaf rolling and flowering of the plant in summer season. 'Alchanggul' grafted onto 'Hidden Power' rootstock was planted on soil bed with the distance of 40 cm. Three ventilation temperatures of 45℃, 40℃, and 35℃ as set points were compared. Ventilation treatment was done by control of side window operation from 18th June to 13th July when silverleaf whitefly, mite, and powdery mildew were occurred in all greenhouses. The temperature inside greenhouse was increased up to the set temperature point on sunny days and maintained for about 9 hours with high relative humidity at 45℃ condition. The differences of day maximum air temperature and day minimum RH were the highest at 45℃ treatment. After 11 days of treatments, the damage by powdery mildew and two-spotted spider mite was almost recovered at 45℃ treatment but not at 40 and 35℃. The population of silverleaf whitefly and two-spotted spider mite were significantly decreased at 45℃ treatment at 14 days after treatment, while powdery mildew symptom was not significantly decreased. Leaf rolling was observed at high temperature but not severe at 45℃ treatment. After 26 days of treatments, female flowers did not bloom at all at 45℃ treatment, and the number of male flowers was 1.2 among 15 nodes of newly grown shoots. As the result, it indicates that ventilation at the high temperature of 45℃ for about 2 to 3 weeks can be an applicable method to control above mentioned pests and disease, and to recover the vegetative growth of Korean melon by reducing flowering of the plant.

• The Korean Journal of Pesticide Science
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• v.17 no.4
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• pp.448-453
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• 2013

We investigated the occurrence of major pests, 4 species of moths (Grapholita dimorpha Busck, Carposina sasakii Matsumura, Archips breviplicanus Walsingham, Adoxophyes orana Fischer von Roslerstamm), apple aphid (Aphis spiraecola Patch), two spotted spider mite (Tetranychus urticae Koch) and parasitoids in pear orchard with hairy vetch and cutting weeds in Yesan, Chungnam province during the flowering season and summer depression season of hairy vetch, in 2012 and 2013. The occurrence of 4 species of moths in hairy vetch plot and cutting weeds (major is finger grass, Digitaria sanguinalis, 80%) were little different but in case of apple aphid, the density in hairy vetch plot was just 95 aphids per stem at 20th June but low after then. The density of two spotted spider mite on pear leaf in hairy vetch plot was lower than in cutting weeds plot significantly. The number of parasitoids collected in hairy vetch plot during flowering season (May and June) were 398 and 798 in 2012 and 2013, respectively. The number of parasitoids collected in hairy vetch plot during summer depression season (July and August) were 114 and 172, respectively. But in cutting weeds plot, 9 and 22 in May and June, 8 and 5 in July and August. We didn't know either hairy vetch in pear orchard affected the occurrence of 4 species of moths, apple aphid and two spotted spider mite or not but was acted to be favorable for wasps, the natural enemies on the contrary. The improvement of chemical control systems through the selection of low chemicals to natural enemies with cover and green manure plants would turn effective pest management into a possibility.

• Korean Journal of Organic Agriculture
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• v.14 no.3
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• pp.315-323
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• 2006

The potential of the predatory mite Phytoseiulus persimilis (Acarina : Phytoseiidae) to control two spotted spider mite Tetranychus urticae (Acarina : Tetranychidae) was investigated on sustainable strawberry fields in Jeonnam area. The density of T. urticae increased from 4th and 7th weeks after single and two timings release P. persimilis, respectively. On the three timings of release plot, number(density) of T. urticae on a leaf maintained fewer than 10 during the 15 weeks after release. In the 1,000 release of P. persimilis per $100m^2$ plot, P. persimilis could not suppress T. urticae. In the 2,000 release plot, P. persimilis could suppress T. urticae with low density which was the similar in the 3,000 release plot. Two-spotted spider mite, T. urticae, occurred from late March and increased density in Hampyeong area. In the P. persimilis released field, T. urticae inhibited continuously after release. In Boseong area, density of P. persimilis increased 50 per 10 leaves through increasing of T. urticae. Percent of occurrence of T. urticae showed high $10.5{\sim}75.5%$ in none-release predatory mite but not high in release treatment. T. urticae on sustainable strawberry field could be inhibited by P. persimilis.