• Korean Journal of Weed Science
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• v.15 no.1
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• pp.19-29
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• 1995

The effect of seeding depth on the growth, mesocotyl elongation and herbicidal response of rice(Oryza sativa L., Japonica type, cv. "Tongjin") and barnyardgrass(Echinochloa crus-galli Beauv. var orizicola Ohwi.) were studied in greenhouse experiments. Barnyardgrass growth as affected by different water depths was briefly tested. Rice and barnyardgrass were broadcast in soil into Oem, 1cm, 2cm and 3cm in seeding depth under dry direct-seeded condition. Butachlor(N-(buthoxymethyl)-2-chloro-N-(2,6-diethylphenyl) acetamide) at dose rate of 1800g ai/ha and thiobencarb(S-[(4-chlorophenyl)methyl] diethyl carbamothioate) at dose rate of 2100g and 4200g ai/ha were soil applied to them at 5 days after seeding. At 10 days after seeding, plants harvested to examine their growth as affected by seeding depth. Root length and shoot fresh weight of rice untreated was greatest in 1cm- and 3cm-seeding depth, respectively, however, mesocotyl did not elongate. While plant height of barnyardgrass grew regardless of seeding depth and water depth, but root length was greatest in 1cm-seeding depth of dry condition and reduced with increased water depth. And mesocotyl was elongated in only dry condition and its length increased with increased seeding depth. At 10 days after application thiobencarb applied pre-emergence inhibited plant height, and shoot fresh weight of rice in only 0cm-seeding depth under dry condition whereas was unaffected in above 1cm-seeding depth, similar to untreated control, and ever increased root length and root fresh weight of rice. On the other hand, shoot, root and leaf growth of barnyardgrass was, severely inhibited regardless of application rates and seeding depths. Reduction of shoot growth by treatment of herbicide was significantly greater than that of root growth. Consequently, reduction of barnyardgrass growth by treatment of thiobencarb did not be associated with seeding depth and mesocotyl elongation as affected by different seeding depth.

• Korean journal of applied entomology
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• v.55 no.4
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• pp.421-429
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• 2016

Tenebrio molitor larvae contain large amounts of proteins, lipids and other functional materials, enabling this insect to be used as an edible food source in animal feeds and for industrialization. Although many efforts have been made to set up mass rearing systems, few studies have been conducted to establish optimal rearing conditions for the production of high quality T. molitor larvae. Herein we investigated 1) the effects of additional diets on the survival and fecundity of the insect, 2) the relationship between oviposition period and the uniformity of larval size, 3) the effects of rearing density and temperature on insect development, and 4) the storage stability of eggs and pupae at low temperatures given possible temporary production discontinuation. The addition of carrot and zucchini to the traditional wheat bran diet significantly increased the survival and fecundity rate of adult T. molitor. Of the three different oviposition sampling periods (3, 7, and 14 days) used to investigate the uniformity of the hatched larvae in each treatment, the period of 3 and 7 days provided higher uniformity than the 14 days oviposition period. Larval development was faster at $30^{\circ}C$ than at 20, 25, and $35^{\circ}C$. Interestingly, oviposition rates were highest at $20^{\circ}C$ but showed much slower larval development and lower uniformity at $30^{\circ}C$. Regarding the effect of larval rearing densities (1, 10, 20, 30, 40, and 50 larvae per 90 mm diam. dish), larval weight was significantly reduced at higher rearing densities, but larval longevity and length were not influenced by rearing density. The 30 larvae/dish is suggested to be a reasonable density to be applied to mass production systems. When kept at $4^{\circ}C$, T. molitor eggs showed a significant reduction in hatching rate; however, when stored under the same conditions, pupae emergence rates remained high until 10 weeks, suggesting that storage at low temperatures is more suitable for the pupal stage than the egg stage. Our findings suggest that an increase in T. molitor adult survival and fecundity rates and a uniformity of hatched larval development can be achieved with the following recommendations: a combination diet (including wheat bran), a 7-day oviposition period; a larvae-rearing temperature of $30^{\circ}C$, a rearing density of 30 larvae/dish, and the storage of pupal stages at low temperatures in the case of rearing discontinuation. This study serves as a strong foundation for the successful mass production of high quality T. molitor larvae.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.4
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• pp.554-562
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• 2003

Xylitol has been used as sugar substitute to prevent dental caries. It is not fermented by most dental plaque bacteria and interferes with the growth of mutans streptococci. Therefore the production of acidic metabolites and the growth of mutans streptococci are inhibited. S. mutans strains which are inhibited to grow under the presence of xylitol are referred as xylitol-sensitive ($X^S$) strains. However, experimental and clinical studies have shown that there were mutated groups of S. mutans strains that are not affected by xylitol. They are referred as xylitol-resistant($X^R$) strains. The aim of the present study was to investigate that emergence of $X^R$ strain would effect on the anticariogenecity of xylitol by comparing the growth rate, the extracellular pH, hydroxyapatite adhesion and the agglutination of the $X^R/X^S$ strains. Overall we came out with following results : 1. No difference in the growth rate and the extracellular pH was found between the $X^S$ strain and the $X^R$ strain. 2. No difference in adhesion to hydroxyapatite surface was found between the $X^R$ strain and the $X^S$ strain (p>0.05) and adhesion of the $X^S$ strain was greater than that of $X^R$ strain in the sucrose-dependent adhesion to hydroxyapatite (p<0.05). 3. The $X^R$ strain was agglutinated in the lower concentration of saliva than that of $X^S$ strains.

• Korean journal of applied entomology
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• v.49 no.4
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• pp.305-312
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• 2010

The developmental time of immature stages of Paromius exiguus (Distant) was investigated at nine constant temperatures (15, 17.5, 20, 22.5, 25, 27.5, 30, 32.5, $35{\pm}1^{\circ}C$), 20-30% RH, and a photoperiod of 14:10h (L:D). Eggs did not develop at $15^{\circ}C$, and their developmental time decreased with increasing temperatures. Its developmental time was longest at $17.5^{\circ}C$ (28.2 days) and shortest at $35^{\circ}C$ (5.9 days). The first nymphs failed to reach the next nymphal stage at 17.5 and $35^{\circ}C$. Nymphal developmental time decreased with increasing temperatures between $20^{\circ}C$ and $32.5^{\circ}C$, and developmental rate was decreased at temperatures above $30^{\circ}C$ in all stages except for the fourth nymphal stage. The relationship between developmental rate and temperature fit a linear model and three nonlinear models (Briere 1, Lactin 2, and Logan 6). The lower threshold temperature of egg and total nymphal stage was $l3.8^{\circ}C$ and $15.3^{\circ}C$, respectively. The thermal constant required to reach complete egg and the total nymphal stage was 109.9 and 312.5DD, respectively. The Logan-6 model was best fitted ($r^2$=0.94-0.99), among three nonlinear models. The distribution of completion of each development stage was well described by the 3-parameter Weibull function ($r^2$=0.91-0.99).

• Korean journal of applied entomology
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• v.59 no.3
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• pp.243-250
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• 2020

Two meridic diets, N4 and N6, containing pinto bean, wheat germ, soybean, whole milk and sucrose as main nutrients were developed for rearing Spodoptera frugiperda (Noctuidae) larvae. Six larval instars were observed when neonate larvae were individually raised on these diets in small petri-dishes (ø 50 × 10 mm, 19.6 ㎤) at 25℃ and 15:9 h (light:dark) photoperiod. The average pupation rate of 97.8% on the N4 diet was significantly higher than the rate of 85.6% on N6 diet. The emergence rates were 92.0% on N4 diet and 93.5% on N6 diet, with a non-significant difference. The larval periods were 17.9 and 17.7 days for females, and 18.7 and 18.5 days for males, for N4 and N6 diets, respectively, with non-significant differences between diets and sexes. The pupal periods on both diets were identical (11.1 days for females and 12.8 days for males), despite differences between sexes. The pupal weights of both sexes on N4 diet were identical with a value of 257 mg, whereas those on N6 diet were 256 and 263 mg for females and males, respectively, with a non-significant difference. The longevity of female adults that emerged on N6 diet was 13.8 days and longer than 8.6 days on N4 diet. The pre-oviposition periods were 5.0 and 4.2 days on the N4 and N6 diets, respectively, with a non-significant difference, however, the oviposition period of 6.5 days on N6 diet was longer than the period of 3.9 days on N4 diet. The effective fecundity on N6 diet was 1,392 eggs (maximum 1,776) and was higher than that of 942 eggs (maximum 1,694) on N4 diet, with a non-significant difference. The egg hatching rates on N4 and N6 diets were 79.2 and 79.8%, and egg periods were 3.0 and 2.9 days, respectively, with non-significant differences.

• Journal of Sericultural and Entomological Science
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• v.50 no.2
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• pp.63-70
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• 2012

This study was conducted to investigated the distribution, ecological character and life cycle of Black Soldier Fly(BSF), Hermetia illucens, to determine effects of BSF on composing ability to the livestock feces. The distribution of BSF was defined in all parts of the country in Korea. Its main habitat was found to be areas near cattle sheds, feces sheds, living waste dump grounds, and food waste dump grounds. Excellent species of the bio-conversion using the livestock feces were selected out of two kinds of solider flies(Hermetia illucens and Ptecticus tenebrifer). And effects of BSF on composing ability to the livestock feces were pig feces 0.5 g, cattle feces 0.43 g and chicken feces 0.3 g per a larvae of BSF. In the examination of the ability of BSF to decompose food waste, volume of the livestock feces decreased by weight pig feces 77, cattle feces 83.62 and chicken feces 80%. Observed characteristics of BSF larvae and pupae stage were by developmental stage may be summarized as follows: size and length of larvae and pupae of BSF were higher than in pig feces and mixed sawdust treatments. In order to develop artificial indoor rearing techniques, The pupation and emergence rate were not visible the difference but important factor of the mating and egg-laying was a sun light. And it was visible the difference in mating ratio. Mating rate of H. illucens by seasonal change was the highest from May to July. Mating mostly occurred between 10 : 00 and 12 : 00 during which light intensity is high. As the egg-laying medium for artificial egg collection, calf feed and food waste were most effective. The ratio of egg-laying medium is waste food : sawdust(1 : 1) in volume. For egg-laying materials, flower foam and wood with holes were used; holes sized 3 ~ 5 mm in diameter, 7 ~ 10 mm in depth were most preferred for egg-laying.

• Korean journal of applied entomology
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• v.62 no.4
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• pp.315-323
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• 2023

The brassica leaf beetle, Phaedon brassicae Baly (Coleoptera: Chrysomelidae), is one of the important pests infesting cruciferous vegetables. In order to understand the biological characteristics of the insect, we investigated the effects of temperature on development of each life stage, adult longevity and fecundity of P. brassicae at four constant temperatures of 15, 20, 25 and 27.5℃ for immature life stage and five constant different temperatures of 10, 15, 20, 25 and 27.5℃ for adult stage. Eggs and larvae successfully developed next life stage at temperature tested. The development period of egg, larva, and pupa decreased as temperature increased. Lower developmental threshold (LDT) and thermal constant (K) were calculated using linear regression as 8.7℃ and 344.73DD, respectively. Lower and higher threshold temperature (TL and TH) from egg to adult emergence were estimated by Briere function as 5.3℃ and 40.4℃, respectively. Adults produced eggs at the temperature range between 10℃ and 27.5℃, and showed an estimated maximum number, ca. 627.5 eggs at 21.7℃. Adult oviposition models including aging rate, age-specific survival rate, age-specific cumulative oviposition, and temperature-dependent fecundity were constructed. Temperature-dependent development models and adult oviposition models would be useful components to understand the population dynamics of P. brassicae and to establish the strategy of integrated pest management in cruciferous crops.

• Korean Journal of Environmental Agriculture
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• v.22 no.3
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• pp.185-191
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• 2003

The mechanism imparting salt tolerance to crop plants remains still unsolved, although soybean has been classified as a susceptible plant to NaCl. To determine optimum parameters on physiological responses for improving sensitivity of salinity in breeding program, soybean (Glycine max Merr., cv. "Gwan-gan") plants were grown in a greenhouse, treated 20 days after emergence for 7 days with NaCl at 0, 30, 60, and 90mM, corresponding to electric conductivity of 1.2, 4.4, 7.3, and 10.4 dS/m, respectively, and assessed 30 days after treatment. Chlorophyll contents were significantly decreased by NaCl ($0.4{\sim}1.0\;mg/g$) compared to control (1.2 mg/g). Photosynthesis rate by NaCl treatment at $0{\sim}90\;mM$ at flowering stage was ranged from 5.0 (control) to $9.6\;{\mu}mol/m^2/s$. Oxygen for respiration was consumed from 5.4 to $9.7\;{\mu}mol/m^2/s$ so that the ratio of $O_2$ (evolution:consumption) was increased with the increase of NaCl, indicating that $O_2$ consumption seems to go beyond $O_2$ evolution. Water potential of leaf at vegetative stage II was ranged from -0.6 to -1.8 MPa and the highest level was observed at mid-day. Water potential by salt stress was decreased with range of $-2.1{\sim}-2.7MPa$ compared to control. Transpiration was decreased from 17% to 20% by NaCl stress. Water vapor diffusing resistance of intercellular air space was affected significantly, increasing up to $16{\sim}24%$ compared to control by NaCl treatment. Salt-treated soybean tended to accumulate $Na^+$, specially in root, with reduced absorption of N, P, $K^+$, $Ca^{2+}$, and $Mg^{2+}$ contents. Free proline content of soybean leaf as affected by different NaCl concentrations was increased 4.2 times ($184{\sim}434\;{\mu}g/g$) more than control. NaCl also increased activities of nitrate reductase and peroxidase by $28{\sim}161%$ and $3{\sim}22%$, respectively. The results show that physiological characteristics of soybean plants during assay were useful as the best parameters of salt stress or salt tolerance test to improve sensitivity in screening and breeding program among cultivars or germplasms.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.2
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• pp.235-240
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• 2012

This study was conducted to find out the optimum cropping system for the stable production of forage crops in the newly reclaimed land located at Gwanghwal region of Saemangum reclaimed land in which the soil is sandy loam (Munpo series). There were two treatments of nitrogen fertilization 20% increment based on the standard fertilization of 150, $200kg\;ha^{-1}$. Whole crop barley as the winter crop sowed on 27 October. After the whole crop barley was harvested at the end of May. Corn and sorghum${\times}$sudangrass as the summer crop sowed at the early of June successively on the same field. Emergence rate the whole crop barley was high while the summer crops were low. Soil salinity was increased during cultivation of summer crops. However, corn and sorghum${\times}$sudangrass were not damaged by salt. Increase of nitrogen fertilization made the growth of cultivation crops good, stem and leaf tended to have a lot of the mineral nutrients at heading stage and silking stage. After experiment, among soil chemical properties pH, content of exchangeable sodium were decreased and content of organic matter, available phosphate were increased. Dry matter yield were showed whole crop barley $13,170kg\;ha^{-1}$ and sorghum${\times}$sudangrass $19,440kg\;ha^{-1}$ by increment of nitrogen fertilization. Therefore, to improve the product and nutrient balance of reclaimed saline land comprehensive soil management should be considered.

• Korean journal of applied entomology
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• v.52 no.2
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• pp.133-140
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• 2013

The developmental times of the immature stages of Sogatella furcifera (Horvath) were investigated at ten constant temperatures (12.5, 15, 17.5, 20, 22.5, 25, 27.5, 30, 32.5, $35{\pm}1^{\circ}C$), 20~30% RH, and a photoperiod of 14:10 (L:D) h. Eggs were successfully developed on each tested temperature regimes except $12.5^{\circ}C$ and its developmental time was longest at $15^{\circ}C$ (22.5 days) and shortest at $32.5^{\circ}C$ (5.5 days). Nymphs successfully developed to the adult stage from $15^{\circ}C$ to $32.5^{\circ}C$ temperature regimes. Developmental time was longest at $15^{\circ}C$ (51.9 days) and it was decreased with increasing temperature up to $32.5^{\circ}C$ (9.0 days). The relationships between developmental rate and temperature were fitted by a linear model and seven nonlinear models (Analytis, Briere 1, 2, Lactin 2, Logan 6, Performance and modified Sharpe & DeMichele). The lower threshold temperature of egg and total nymphal stage was $10.2^{\circ}C$ and $12.3^{\circ}C$ respectively. The thermal constant required to complete egg and nymphal stage were 122.0 and 156.3 DD, respectively. The Briere 1 model was best fitted ($r^2$= 0.88~0.99) for all developmental stages, among seven nonlinear models. The distribution of completion of each development stage was well described by three non-linear models (2-parameter, 3-parameter Weibull and Logistic) ($r^2$= 0.91~0.96) except second and fifth instar.