• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.2
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• pp.195-205
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• 2020

Oceanic conditions in walleye pollock habitat in the East Sea have shown decadal fluctuations between warm and cold periods in turn. Specifically, sea surface temperature (SST) has shown a dramatic increase between the late 1980s and the middle 2000s, and abrupt decreasing patterns after the late 2000s. Oceanic conditions in the Dong-han Bay (spawning ground) and middle eastern coastal waters (fishing ground), however, indicated different fluctuation trends in SST, increasing in the Dong-han Bay after the late 1980s, and decreasing after the late 2000s. These fluctuation patterns were especially clear in February and March. Sea surface temperature in the middle eastern coastal waters of Korea soared continuously after the late 1980s, but did not show a distinct decreasing pattern after the late 2000s compared with Dong han Bay, except for February SST values. These long term water temperature changes in both walleye pollock spawning and fishing ground are related to variation in walleye pollock landings. Especially, abrupt changes in spawning ground SST can be one of the factors influencing survival in the early ontogenesis of walleye pollock, including egg and yolk larval stages. During the 1980s, the area of suitable spawning temperature (2-5℃) was wider, and the length of Walleye pollock egg and larval stages greater compared with past and present oceanographic environments. However, such patterns did not correspond with the optimal spawning temperature range and greater length of development of walleye pollock during the late 1980s likely triggering a decline in pollock stock. In conclusion, it has been supposed that the dramatic decrease in walleye pollock landings in the East Sea since the late 1980s was caused by increasing water temperature leading to both early mortality and unsuitable spawning conditions.

• Journal of Korean Society of Forest Science
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• v.89 no.5
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• pp.685-690
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• 2000

Caliroa carinata (Zombori) has heavily damaged the forests of Quercus mongolica in Sangju, Kyongbuk, Korea since 1996. However, information on the ecology and control of this pest was badly scarce. Thus we tried to study the ecology and chemical control of the sawfly through this study. Caliroa carinata is one generation per year. The adult sawflies emerged from June 8 to July 5 with peak at June 18. A female adult laid 11 eggs in rows on the backside of a leaf along the midribs and larger veins. Larvae have six instars, and the developmental period required to complete the larval stage was 19 days and 17 days at temperatures of $20^{\circ}C$ and $25^{\circ}C$, respectively. Each larval stage required 2-4 days to complete the development. The sawfly mostly preferred Quercus mongolica and Q. dentata, while avoiding Q. variabilis. Such insecticides as Tebufenozide, Flufenoxuron, Etofenprox, and Fenitrothion were sprayed on host plant leaves infected with test larvae in order to study the mortality. After 3 days of insecticide treatments, the mortalities were thoroughly examined. All insecticides showed higher than 95% of mortalities. Control values were also higher than 93%. The optimal season of insecticide application for pest control was estimated from late June to early July.

• International Journal of Industrial Entomology and Biomaterials
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• v.23 no.2
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• pp.215-221
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• 2011

To establish an indoor-rearing system for the Large Copper butterfly, $Lycaena$ $dispar$ and the Small Copper butterfly, $Lycaena$ $phlaeas$, the effect of temperature, photoperiod and host plants on larval development was investigated. The larvae of $Lycaena$ $dispar$ fed on $Rumex$ $crispus$, whereas the larvae of $Lycaena$ $phlaeas$ ate both $Rumex$ $crispus$ and $Rumex$ $acetosa$. The duration of the larval period of $Lycaena$ $dispar$ was 13.8 days on $R.$ $crispus$ and that, of $Lycaena$ $phlaeas$ was 15.9 days and 15.2 days on $R.$ $acetosa$ and $R.$ $crispus$ respectively. Laboratory experiments show that the Large Copper larvae are able to feed on other $Rumex$ species without harming their overall survival and can utilize these alternative host plants at least as efficiently as their natural host plant. This result suggests that plant chemistry is not responsible for their lack of utilization of the alternative host plants in the wild. Host plant choice by ovipositing females was measured with the two alternative hosts. $Lycaena$ $dispar$ preferred $R.$ $crispus$ to $R.$ $acetosa$, wheareas $Lycaena$ $phlaeas$ preferred $R.$ $acetosa$ to $R.$ $crispus$. Temperature has been proposed as an important determinant of developmental rate, lifespan and mortality in invertebrates. As temperature increased, length of the developmental period gradually decreased. The developmental period of the Large Copper larvae was 11.0 days and 28.5 days at $30^{\circ}C$ and $17.5^{\circ}C$, respectively.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.13 no.2
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• pp.140-146
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• 2008

Marine ecotoxicological standard method using fish larvae was established with the standard test species of Oryzias latipes(Japanese Medaka) and Paralichthys olivaceus(flounder) and with the 7 day $LC_{50}$ as endpoint. Test method referred to the USEPA(1994) with the replacement of test species found in the Korean water. Standard test species were selected in terms of the species supply and ecological importance in Korean waters. Japanese medaka can be reared with small tanks in the lab and has wide tolerance on salinity, and flounder eggs can be easily obtained from commercial fish hatcheries. General conditions for larval fish toxicity test are as follows. The possible salinity ranges for toxicity test were $0{\sim}35\;psu$ for medaka and >20 psu for flounder. Test type was designated as static non-renewal test if the dissolved oxygen in the test chamber does not fall below 4.0 mg/L. Ages of test species were selected as 7 days after hatched for medaka(about 5 mm TL) and 25 days for flounder(about 10 mm TL) because of the low natural mortality after these periods. Test can be accepted when the survival rates are over 80% in control. Also, species sensitivity on standard reference materials(copper, cadmium or zinc) must be provided with the toxicity test results.

• Korean Journal of Environment and Ecology
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• v.26 no.5
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• pp.675-681
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• 2012

In this experiment, I investigated toxicity evaluation of chemicals using domestic frog embryos, along FETAX (Frog Embryo Teratogenesis Assay-Xenopus) protocol. I investigated $Cu^{2+}$ and Tebuconazole effect on the tree frog, Hyla japonica, embryos by probit analysis. Mortality and malformation rates increased and larval body length decreased depending on the concentrations of $Cu^{2+}$ and Tebuconazole. The teratogenic concentration ($EC_{50}$) of $Cu^{2+}$ and Tebuconazole were 0.05, 5.0mg/${\ell}$, respectively and the embryo lethal concentration ($LC_{50}$) of $Cu^{2+}$ and Tebuconazole were 0.16, 38.5, respectively. The teratogenic index (TI) appeared 3.0 in $Cu^{2+}$ and 7.7 in Tebuconazole, which showed teratogenicity in embryonic development of Hyla japonica. These results reveal that $Cu^{2+}$ and Tebuconazole in this experiment suppressed the development of embryos at relatively low concentration. Much of Hyla japonica embryos can be secured, and easy to incubate. In addition, mortality, malformation ratios, malformation patterns and growth rates are similar to the results from the other assay systems. Therefore, the Hyla japonica embryo teratogenesis assay system could be a useful tool to evaluate toxicity of pollutants in environment.

• International Journal of Industrial Entomology and Biomaterials
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• v.19 no.2
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• pp.237-241
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• 2009

The objective of our study was the evaluation of pathogenicity of a local strain of Mamestra brassicae nucleopolyhedrovirus-K1 (MabrNPV-K1) derived from a diseased larva of M. brassicae found in Korea. The effect of temperature and larval instar on the pathogenicity and production of MabrNPV-K1 was determined under laboratory conditions. The median lethal concentration ($LC_{50}$) values of MabrNPV-K1 for 3rd instar larvae were $3.7\times10^4$ PIBs/larva at $20^{\circ}C$, $9.9\times10^2$ PIBs/larva at $25^{\circ}C$ and $3.8\times10^2$ PIBs/larva at $30^{\circ}C$, respectively. The $LC_{50}$ for the 4th instar larvae was similar to that for the 3rd instar larvae. However, the pathogenicity to the 3rd instar larvae was higher than that to the 4th instar larvae. The median lethal time ($LT_{50}$) values of MabrNPV-K1 were 11.4 to 5.0 days at $30^{\circ}C$ and 18.3 to 5.5 days at $25^{\circ}C$ for the 3rd instar larvae. The $LT_{50}$ value was lowered as temperature went up to $30^{\circ}C$ and dependent on viral concentration. In production efficiency of MabrNPV-K1 using M. brassicae larvae, the mortality of the 3rd instar larvae was 100% when inoculated with $1.0\times10^5$ PIBs/larva and the yield of MabrNPV-K1 was maximal. Regarding the mortality, yield of polyhedra, inoculation doses and required time, the $1.0\times10^4$PIBs/larva at $30^{\circ}C$ was determined as optimal conditions producing polyhedra efficiently.

• The Korean Journal of Pesticide Science
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• v.11 no.4
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• pp.299-304
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• 2007

Surveying, laboratory and field trial were performed to elucidate the causes of non-spinning syndrome of silkworm, Bombyx mori, abnormal symptoms of silkworm instars observed in certain sericultural fanning region. Mortality and growth of silkworm was still influenced by feeding the mulberry leaves sprayed with 10,000 fold diluted solution of standard spray of diflubenzuron WP (25%). Mortality and growth of silkworm fed with diflubenzuron-sprayed mulberry leaves with recommended spray solution were entirely affected even six weeks after spraying irrespective to the instars. Larval period of 5th instar and cocooning duration of silkworm was not affected in case 50m of buffer zone has maintained in near-by orchard field sprayed with diflubenzuron WP (25%). However, survival rate of pupae was not influenced in case 100 m of buffer zone has kept. Insect growth regulating insecticides were required to keep a certain distance of buffer zone when sprayed with water-diluted solution, 100 m from the application site at least in order to prevent contamination of the spraying drift by the chemicals.

• The Korean Journal of Pesticide Science
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• v.13 no.1
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• pp.54-61
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• 2009

EPN-resistant diamondback moth were tested the developmental characteristics, longevity, fecundity and synergistic effect with synergists when treated with the bistrifluron, an inhibitor of chitin synthesis. Inhibition rate of egg hatch was below at the recommended concentration (50 ppm) to the EPN-resistant strain than EPN-non selected strain, however, mortality within 24hr after hatching was showed as 50-60%. They did not show the difference between two strains. Mortality of larval instars were showed effective to two strains with no difference. Inhibition rate of emergence did not show any effect when treated with pupae. Moreover, they did not affect to the longevity and fecundity. When bistrifluron was treated at 50 ppm to the adult, however, longevity and fecundity was decreased with no difference between two strains. Bistrifluron to the EPN-resistant strain showed synergistic effect as high as 137.7 and 73.1 folds with synergist such as PBO (microsomal oxidase inhibitor) and polyoxin B (chitin synthetase inhibitor), respectively.

• Journal of Aquaculture
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• v.11 no.2
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• pp.203-212
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• 1998

As seed production program is growing prosperously in various fishes in southern Korea, disease problems in larval and juvenile stages have emerged as a new research object. The following results were obtained from investigation about environmental factors related to mass mortalities of young Kinki red seabream, Pagrus major in process of artificial seedling production. Total length of red seabream larvae hatched was 2.93mm, and became 18.83~20.12mm at day 40. The first noticeable mortality of red seabream larvae (7.98~9.37mm) occurred in 25~30 day-old fish with the survival rates of 59.8~60.3%. Thereafter the mortality of larvae decreased, survival rate was 20.5~25.45% in day 40. After 20~30 days, the quality of pond water was bellow II class. During the experimental period COD, $PO_4$-P, $NO_2$-N, $NO_3$-N and $NH_$-N increased up to 3, 7, 34, 6 and 8 times, respectively, compared to initial ones. The number of viable bacteria in pond water and seabream larvae were $6.3{\times}10^6$~$2.3{\times}10^7$ cfu/ml, 4.3~$7.4{\times}10^6$ cfu/g in day 25, respectively. Among the isolated bacteria from the diseased red seabream in day 25, Vibrio spp. was considered to be the causative organism. External symptoms of this disease were floated, spined near the surface and inflated abdomen. When the isolated strain of the Vibrio was bathed to seabream larvae, $LD_50$ of seabream larvae was over $10^6$ cfu/ml of Vibrio spp.

• Korean journal of applied entomology
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• v.57 no.3
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• pp.151-160
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• 2018

Anoplophora chinensis and A. glabripennis is classified as important quarantine Cerambycidae beetles worldwide. These beetles cause serious damage on natural host plants and export bonsai trees in Korea. We evaluated efficacy of phosphine fumigant for control of two Cerambycidae beetles in bonsai. In the preliminary test to achieve CT (Concentration x time) values of phosphine to Cerambyicdae beetles larvae, we used Monochamus alternatus of larvae as an alternative insect. A 24 h phosphine fumigation with $2g/m^3$ phophine achieved 100% eggs mortality against Anoplophora chinensis and A. glabripennis. Larva of A. chinensis was also completely controlled when treated for 168-h at same dose desiccator. 100% mortality on larval stage of two beetle species were achieved both in dormancy (January) and vegetative period (February) of bonsai when treated with $2g/m^3$ phosphine. However, phosphine fumigation against vegetative period of Acer palmatum, Carpinus turczaninowii and Malus sieboldii bonsai showed slight phytotoxicity (shorten leaf and flower size and delayed flowering).