• The Korean Journal of Ecology
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• v.23 no.1
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• pp.65-70
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• 2000

Field collections were made from six gypsy moth (Lymantria dispar L.) Populations in Kyonggy and Cheju areas during the period 1987∼1997. Characteristics of gypsy moth populations at different phases were examined in terms of egg mass density, relative larval density, plant damage, and fecundity. Males captured in pheromone trap were recorded, and we examined if there was a relationship between numbers captured and the population density during the following generation. Egg mass density was closely related with larval density, and furthermore these densities were correlated with the level of plant damage, indicating that larval dispersion was limited in oviposition areas. The gypsy moth population cycle was short in Korea with the period from population development to innocuous level usually lasting 2∼3 years. Male caught by pheromone trap (mean number of males caught per trap per day in peak emergence period) was positively correlated with egg mass densities in the following season (r²=0.93). A low fecundity was detected from outbreak populations which accompanied defoliation. Fecundity of gypsy moth ranged from 538 to 601 at other phases.

• Journal of the Korea Organic Resources Recycling Association
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• v.15 no.4
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• pp.93-99
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• 2007

Vertical distribution of tiger worm(Eisenia fetida) population in the earthworm rearing bed was investigated with feeding paper mill sludge. More than 50% of larva and adult population of Eisenia fetida lived within the depth of 5 cm from the surface of rearing bed. And more than 96% of the population of larva, adult and cocoon lived within the depth of 20 cm. Percental vertical distribution of Eisenia fetida population in the rearing bed was not much influenced by the changes in the height of rearing bed or density of earthworm population.

• Journal of the Korea Organic Resources Recycling Association
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• v.16 no.3
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• pp.52-64
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• 2008

Aged sewage sludge with food waste leachate sludge or paper mill sludge was fed to earthworm (Eisenia fetida) populations and the effect of it on feeding and growth rate of earthworm population was investigated. Feeding rate of earthworm population on sewage sludge aged with food waste leachate sludge for 30 days was higher than that aged for 10 and 20 days. At 90 days after feeding, the density of earthworm population decreased regardless of aging period. And earthworm population growth to next generation was blocked by sewage sludge. The feeding rate and the density of earthworm population aged with paper mill sludge for 20 days were higher than that on sewage sludges aged for 10 and 30 days. Until 90 days after feeding, the density of earthworm population increased regardless of aging period of sewage sludge, however, since then decreased. There were comparatively higher feeding rate and growth rate of earthworm population on the sewage sludge which had been mixed with paper mill sludge and aged for 20 days, which rendered the probable pretreating method for vermicomposting sewage sludge.

• Korean journal of applied entomology
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• v.18 no.1 s.38
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• pp.15-21
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• 1979

To determine the population regulation mechanism of the Green rice leafhopper (Nephotettix cincticeps Uhler), the responses of the population increase to initial densities and the effect of host conditions and temperatures during developmental period were investigated. In the out door experiment, the increasing ratio of population density of this pest was reduced as initial density increased and this density-dependent effect was differ in accordance with host condition. Host conditioning through feeding resulted in reduction in numbers of eggs produced and it seemed to be affected by some inhibiting materials secreted by the pest during feeding. though the direct effect of feeding can't be excluded. The population growth was related with population density and host stage. Thus in late planted units, the host stage was favourable to the growth of population at low initial insect density but unfavourable at relatively high initial insect density and in early planted units, vice versa. The temperature during developmental stages definitely affected the determination of sex ratio of adult population and reduced numbers of eggs produced. The most favourable temperature to the population increase was $290^{\circ}C$, and at high temperature, $33^{\circ}C$, severe reduction of fecundity was shown ana it seemed to be caused by the simple reduction in numbers of eggs produced.

• Korean journal of applied entomology
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• v.28 no.2
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• pp.61-68
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• 1989

To investigate the possibility of the BPH control by systematic application of insecticides, biological effects of buprofezin and isoprothiolane upon the BPH population was evaluated in the laboratory and pot. Both chemicals did not affect the developmental period of the nymphal stage with the applied dosages. When the buprofezin treated instar nymph was developed to the adult, adult's longevity was fairly reduced and such an effect of buprofezin was greater upon the younger instar nymphs. Residual effect of buprofezin was about 30 days in the pot. And it could suppress the BPH population when the younger instar nymphs were dominant age group in the population at the time of treatment. Isoprothiolane was also more effective for the suppression of the BPH population when the younger instar nymphs were dominant at the time of treatment. And it was expected that by buprofezin treatment in July the control effect of isoprothiolane against the BPH population could be maximized when it was treated to control the rice neck blast in late July or early August, because buprofezin could induce the biased population age distribution in which younger instar nymphs were main group at the time of isoprothiolane treatment.

• Korean Journal of Ecology and Environment
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• v.38 no.2 s.112
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• pp.146-159
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• 2005

Fifty-four zooplankton species from Daecheong Lake were identified during the research period from June to October 2001. The representative zooplanktons mostly comprised the index species indicating the intermediate stage from oligosaprobity to ${\beta}$-mesosaprobity. During the blooming season of blue-green algae, the population of large cladocerans like Daphnia galeata precipitously decreased in size, while rotifers and small cladocerans like Bosmina longirostris increased in population size. Therefore, soon after the peak of the blooming of blue-green algae, whole zooplankton standing crop and number of species showed the tendency of recovery, or even the sharp increase. The population size of Daphnia galeata was affected very sensitively by the change of cyanobacterial density.

• Journal of Korean Society of Forest Science
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• v.97 no.1
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• pp.113-117
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• 2008

This study was conducted to clarify the differences in habitat characteristics and rodent populations between before and after damaged tree removals at forest fired areas in coniferous forest, Samcheok, Gangwon Province, Korea. The understory coverage and the number of shrub stem were increased by forest succession. Number of snags and downed CWD (coarse woody debris) were decreased after damaged tree removals. Population density of Apodemus agrarius was increased after damaged tree removal. However, population density of total rodents, Apodemus peninsulae and Eothenomys regulus were decreased. Changes in habitat structures may be influenced in rodent species composition. Especially, that would be negative effect on forestdwelling rodents.

• Parasites, Hosts and Diseases
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• v.34 no.1
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• pp.27-34
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• 1996

The geographical distribution and population density of rodents and chigger mites at six localities of Chollanam-do were investigated from October to December in 1993. Among total 142 field rodents collected by the modified Chemin wooden traps, 131 rodents were Aponemw usrari,us (92.3%) and 11 were Crocidurc losiurc (7.7%). Out of 142 field rodents, 92 were parasitized by chiggers, showing 69.0% of the infestation rate and 74.2 of the chiggor index. Infestation rate and chigger index of A. omfernrius and C. lusiurc were 73.3%, 80.4 and 18.2%, 0.5, respectively. From the trapped field rodents, 10,532 chiggers were collected and identified with 11 species of 4 genera. Leptotrombidium pcLLinun. the vector 3pecies of tsutsugamushi disease, was the dominant species, showing 8,038 chi99ers (76.31%). L. scutellnre was the second dominant species showing 1,359 chiggers (12.9%). The distribution of chigger mites was clearly localized by the species, showing the different dominant species according to localities. The predominant species was 1. scutellare (100%) in Changhung-gun, 1. scutellcre (41.5%) in Posong-gun, 1. pnllidum (88.8%) in Hwasun- gun, 1. pnLlidunl (59.2%) in Koksong-gun, 1. zetum (77.3%) in Hampyong-gun, and 1. pclpcle (63.4%) in Tamyang-gun. Regarding to the geographical distribution of chigger population density, the infestation rate and chigger index was most high in Hwasun-gun as 62.4% and 216.2 respectively, and next high in Koksong-gun as 22.4% and 77.7%, respectively.

• Korean Journal of Ecology and Environment
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• v.37 no.4 s.109
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• pp.385-393
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• 2004

The herbivorous rotifers community (Brachionus spp.) and population dynamics of the predator rotifer (Asplanchna spp.) in three tributaries (Kumho R., Nam R., and Hwang R.) of the Nakdong River were evaluated on biweekly intervals from Jan. 2001 and Dec. 2002. High abundance of the herbivorous rotifers (peak density: - ca.>1000 Ind. $L^{-1}$) was observed from two tributaries (Kumho R. and Nam R.) during the spring and fall seasons, respectively. The high peaks of herbivorous rotifers were not evident in one tributary (Hwang R.). Among the herbivorous rotifers, brachionid rotifers (Brachionus spp. consisting of 7 species) were the characteristic rotifer community in this study. Brachionus spp. tended to occur together with the other perennial species, Asplanchna. Asplanchna was also present while two species of B. angularis and B. calyciflorus were highest in density. Subsequently, two populations (B. angularis and B. calyciflorus) rapidly declined, becoming rare after high peaks of Asplanchna occurred, except in one tributary (Hwang R.). We found community shifts in rotifer groups in mid-spring and mid-fall at the study site. The Asplanchna population could be appeared to play an important role in regulating the rotifer community and total plankton biomass in spring and fall at high trophic levels.

• Korean journal of applied entomology
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• v.58 no.4
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• pp.347-354
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• 2019

Temperature-dependent traits of Laodelphax striatellus, rice stripe virus vector, were investigated at 10 constant temperatures (12.5, 15.0, 17.5, 20.0, 22.5, 25.0, 27.5, 30.0, 32.5, and 35.0 ± 1℃) under a fixed photoperiod (14/10-hr light/dark cycle). Unit functions for the oviposition model were estimated and implemented into a population dynamics model using DYMEX. The longevity of L. striatellus adults decreased with increasing temperature (56.0 days at 15.0℃ and 17.7 days at 35.0℃). The highest total fecundity (515.9 eggs/female) was observed at 22.5℃, while the lowest (18.6 eggs/female) was observed at 35.0℃. Adult developmental rates, temperature-dependent fecundity, age-specific mortality rates, and age-specific cumulative oviposition rates were estimated. All unit equations described adult performances of L. striatellus accurately (r² =0.94~0.97). After inoculating adults, the constructed model was tested under pot and field conditions using the rice-plant hopper system. The model output and observed data were similar up to 30 days after inoculation; however, there were large discrepancies between observed and estimated population density after 30 days, especially for 1^st and 2^nd instar nymph densities. Model estimates were one or two nymphal stages faster than was observed. Further refinement of the model created in this study could provide realistic forecasting of this important rice pest.