• Korean Journal of Agricultural and Forest Meteorology
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• v.25 no.3
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• pp.142-150
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• 2023

As global warming continues, the time of invasion of Spodoptera frugiperda has been advanced and the inflow rate has been increasing, leading to great increases in damage to crops. In this study, in order to minimize crop damage caused by S. frugiperda, the control period was set for corn fields through control thresholds, and the control effects according to the chemical spraying methods were investigated in forage corn filed. Even under the condition of 4% injury level during the corn silking stage, the damage rate of ear was 70%, showing an aspect of extensive damage. The economic injury level of S. frugiperda second instar larvae was shown to be 0.7 larvae per stalk, and the control threshold level was shown to be 0.6 larvae. The income was calculated by applying the corn wholesale unit price, and according to the result, even under the condition of injury level of 4%, there was a loss of KRW 895,221/10a, and the higher the injury level, the greater the decrease in income. To control S. frugiperda, the insecticidal effects of 10 single formulations registered for S. frugiperda were tested, and according to the results, four types(emamectin benzoate, chlorantraniliprole, indoxacarb, and spinetoram) showed high insecticidal activity not lower than 93.3%, and three types (chloran- traniliprole, spinetoram, and indoxacarb) were considered to be effective in controlling S. frugiperda as they showed high residual effects through insecticidal effect persistence tests. Therefore, conventional control and aerial control were conducted twice at 7-day intervals with indoxacarb SC and chlorantraniliprol WP, which show high activity against S. frugiperda, respectively, prior to the silking of forage corn. As a result, conventional control showed higher control values, 46.3%p in the case of indoxacarb SC and 21.7%p in the case of chlorantraniliprol WP, than aerial control through the primary control. In the secondary control too, higher control values of 26.7%p in the case of indoxacarb SC and 40.4%p in the case of chlorantraniliprol WP were found in conventional control than in aerial control. Therefore, it is considered necessary to prepare measures to improve the control effects in the recent situation where alternative methods for manpower control are widely used.

• Korean journal of applied entomology
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• v.47 no.4
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• pp.395-400
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• 2008

Economic injury levels (EILs) and economic threshold (ET) were estimated for the two spider mite, Tetranychus urticae Koch (Acari, Tetranychidae) on greenhouse eggplants. T. urticae density increased until the mid-July and thereafter decreased in all plots where initial density of the mite were different each 0, 2, 5, 10 and 20 adults per plant was innoculated on June 7. Growth variables of were not different among experimental plots but fruit weights were lower in plots with higher initial mite density than in plots with lower initial mite density. Total number of fruits and the number of marketable fruits decreased in plots with higher initial mite density. The rates of yield loss increased with increasing initial mite density, resulting in 0, 3.9, 11.3, 14.5, 22.8% reduction in each of the above plots, respectively. The relationship between initial T. urticae densities and yield losses was well described by a linear regression, Y = 1.085X + 2.474, $R^2$ = 0.9659. Based on the relationship, the number of adults per plant which can cause 5% loss of yield was estimated to be approximately 1.8.

• Korean Journal of Organic Agriculture
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• v.22 no.2
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• pp.347-357
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• 2014

This study was conducted to evaluate the control effect of sodium dichloroisocyanurate (NaDCC) for Venturia nashicola on Niitaka pear during flowering period. As a nontoxic disinfectant, sodium dichloroisocyanurate is widely used in the field of hygiene and disease prevention, medical treatment, aquiculture as well as plant protection. NaDCC was sprayed on the pear tree inoculated with conidia ($4.5{\times}10^5spores/mL$) of Venturia nashicola and as a result the incidence of pear scab was 23.8% in 750mg/L and 26.2% in 1,000mg/L compare to the 51.6% incidence in untreated tree. No damage in the pollen of pear flower was detected with NaDCC treatments in the full bloom period for six pear cultivar including Wonwhang. A NaDCC single treatment in the early bloom of Niitaka pear showed more than 98% of fertilization rate. Furthermore, there was no incidence of Venturia nashicola on Nitaka pear trees treated with NaDCC 4 times during their growth period.

• Korean Journal of Agricultural Science
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• v.30 no.1
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• pp.11-19
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• 2003

The life-cycle of the aphid-parasite, Aphidius gifuensis, took 11.9 days at $25^{\circ}C$ and 12.1 days at $30^{\circ}C$. The female appearance rate of A. gifuensis was the best at $20{\sim}25^{\circ}C$ compared to the other temperatures. Optimum rearing temperature of Aphidius gifuensis was $20{\sim}25^{\circ}C$ Optimum temperatures for A. gifuensis emergence were $20^{\circ}C$ and $25^{\circ}C$ with 99.1% and 98.2%, respectively. However the emergence rate of Aphidius gifuensis was 58.8% at $10^{\circ}C$. There was a positive correlation between A. gifuensis adult activity and temperature, but there was a negative correlation between developmental period of Myzus persicae nymph and temperature. Among the pests occurring in pepper greenhouse, dominant species was M. persicae and its density was 6~1,024 per plant. The damaged fruit rate by Helicoverpa assulta was 3.3~53.3%. The number of aphid and mummy in the A. gifuensis released plot were 173.5 and 10 in June, 1.8 and 17 in July, 2000, respectively. The numbers of Aphidius gifuensis were 7.5 and 0.4 in May, 27.1 and 2.1 in June, 2001, respectively. The suppressive effects on M. persicae in A. gifuensis released plot was better than the control plot, but there was no significant difference compared to the pesticide-sprayed plot. The first leaf length and the stem width in the A. gifuensis released plot, the control plot, and the pesticide-sprayed plot were not significantly different, but the A. gifuensis released plot showed the highest yield among the plots.

• Korean journal of applied entomology
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• v.53 no.3
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• pp.209-215
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• 2014

This study was performed to monitor the seasonal occurrence of Pseudococcus comstocki (Kuwana) by using pheromone traps and to test a mating disruption technique to control this pest in pear orchards. We compared the attractiveness of rubber septa loaded with 1.5 and 3.0 mg of the pheromone, 2,6-dimethyl-1,5-heptadien-3-yl acetate. A total of 1,021 and 1,431 males were caught in traps baited with 1.5 mg and 3 mg of the pheromone, respectively. The numbers of males caught were not affected by trap color, although yellow traps were more attractive than white traps. In 2012, P. comstocki males were captured between June and October, with peaks in late June, early August, and late September. In 2013, the males were trapped between June and October, with peaks in middle June, late July, and late September. In pheromone mating disruption tests, catches were reduced by 17.7, 65.3, and 62.9% in orchards treated with 450, 900, and 1,350 mg per 10 a of the pheromone, respectively. At harvest, 3.4, 2.9, and 4.8% of fruits in orchards treated with 450, 900, and 1,350 mg per 10 a were damaged by P. comstocki, while 9.5% were damaged in the control orchard.

• Korean journal of applied entomology
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• v.54 no.3
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• pp.191-197
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• 2015

Fruit drop due to Eurytoma maslovskii infestations of Japanese apricot (Prunus mume) is a serious economic issue in most parts of Jeonnam Province, with the exception of the coastal areas such as Wando, Shinan, Yeosu, and Muan. The average incidence of fruit drop was 67% in 2013 and 33.3% in 2014. E. maslovskii larvae overwinter inside the pits of Japanese apricots. Larval survival rates decrease to less than 30% after a rainy summer season. The eggs are long oval of 0.68 mm, 0.29 mm and ivory white. Mature larva is of 6.56 mm, 3.18 mm. Free pupa are black, adult females and males of 6.97 mm, 4.90 mm lengths, respectively, while the ovipositor is 0.64 mm in length. Adult emergence occurs from early April to early May, when Japanese apricot fruits are from 4 mm to 17 mm in diameter. Adults persist for 13.5 d after emergence, and the sex ratio of females to males was found th be 45.9:54.1. Although up to four eggs may be oviposited per fruit, only one larva will ultimately survive, ans the larvae are cannibalistic. The period during which E. maslovskii is able to oviposit on Japanese apricots only lasts from mid- to late April (fruit diameter: 12~16 mm). When the diameter of the fruit is >16 mm, the pit of the Japanese apricot hardens and larvae have difficultly penetrating the stone. Therefore, the most effective method of controlling this pest is to spray orchards with a control agent 2~3 times, at 5 d intervals, beginning in mid- April.

• Horticultural Science & Technology
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• v.35 no.1
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• pp.69-78
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• 2017

This study was conducted to investigate the effects of waterlogging on the net photosynthetic rate, root activity and fruit yield of hot pepper. Plants were grown in two greenhouses: extractor fans and side ventilators began to operate when the inside temperature reached $25^{\circ}C$ in one greenhouse and $35^{\circ}C$ in the other. Waterlogging treatments were performed 54 days after transplanting (when fruit setting at the second flower truss was complete). The plot in each greenhouse was divided into five sections, and each section was watered for 0, 12, 24, 48 or 72 h using drip irrigation. Plants under $25^{\circ}C$ and non - waterlogging treatment exhibited in the greatest growth among treatments. Plant growth generally decreased as the waterlogging period increased. The net photosynthetic rate was highest under non - waterlogging and $25^{\circ}C$ treatment and lowest under 72 h waterlogging and $25^{\circ}C$ treatment. The root activity decreased as the waterlogging period increased, except for plants under 72 h waterlogging treatment at $35^{\circ}C$. The number and weight of red pepper fruits per plant were highest under non - waterlogging treatment at $35^{\circ}C$. The greatest fruit yield was also observed under non - waterlogging treatment at $35^{\circ}C$, with production reaching 3,697 kg / 10a. At the appropriate temperature for hot pepper ($25^{\circ}C$), yields were reduced by 25 - 30% under 12, 24 and 48 h waterlogging treatment compared to non - waterlogging treatment. These results indicate that longer waterlogging periods reduce the growth, net photosynthetic rate, root activity and yields of hot pepper. However, the net photosynthetic rate and stomatal conductance of hot pepper plants grown under 72 h waterlogging treatment recovered nine days after growth under normal growth conditions.