• Journal of Korean Society of Forest Science
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• v.99 no.3
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• pp.298-303
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• 2010

To explore on the defense strategies against hervivory of Juglans regia and J. mandshurica, morphological characteristics of the leaf, leaf domatia structure and the number, herbivores insects and mites on the leaves, collected from the trees growing in Mt. Chiak, Mt. Cheongtae, Mt. Jungwang, Namyangju-si and Wonju-si, were investigated from May to October, 2009. Domatia of J. mandshurica revealed tuft type, these of J. regia revealed pocket+tuft type. Domatia number per leaflet proved the higher figures, 28.3/leaflet for J. mandshurica, and the lower, 19.6/leaflet for J. regia. Leaf surface trichomes of J. regia revealed stellates only on the domatia structures, and that of J. mandshurica does dense stellates and glandular hairs on the leaf-blade and vein. Predatory mites' number per leaflet proved highly significant differences among tree species, and mean of predatory mites was higher values (4.8/leaflet) in J. mandshurica and lower values (3.5/leaflet) in J. regia. Small amount of nectar are found distal veinparts on the leaf margin of J. mandshurica. Dense glandular hairs on the lower leaf surfaces of J. mandshurica estimates useful strategy against herbivory. It may be possible to breed J. regia for better expression of leaf traits such as dense glandular hairs that increase predator populations and efficacy.

• Korean Journal of Plant Resources
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• v.27 no.2
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• pp.188-193
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• 2014

The sap outflow characteristics of Juglans sinensis and J. mandshurica were investigated to evaluate the optimum pruning period of walnut tree that there is a sap spill on dormant. The total period of sap outflow were 34 days for both J. sinensis and J. mandshurica. Total amount of sap outflow per tree in J. sinensis and J. mandshurica were 2,922 mL/tree and 3,135 mL/tree, respectively and the period of sap outflow and non sap outflow between two species were similar. ANOVA analysis showed that the amount of sap outflow was significant differences with day of sap outflow but there were no significant differences between species. From the correlation analysis between air-temperature and sap outflow, daily minimum temperature showed a positive correlation at the 1% level of significance (r=0.56 and r=0.46) for both J. sinensis and J. mandshurica. When branch of walnut tree that diameter is 5 cm cut on the period of sap outflow, the sap flowed down the longest period (48 days) but the sap outflow was not observed after budburst. Therefore, our study supported that the pruning have to avoid the period of sap outflow to reduce sap outflow of walnut tree.

• Research in Plant Disease
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• v.17 no.3
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• pp.386-390
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• 2011

In June 2011, walnuts (Juglans regia) from orchards in Kimcheon and Muan, in southern Korea, were found to exhibit downy mildew-like symptoms of a foliar disease. Whitish polygonal efflorescence was produced on the abaxial surface of affected leaves and discolored light green blotches on the corresponding adaxial surfaces. In the later stage of disease development, diseased tissues collapsed and became necrotic. Based on morphological and cultural characteristics, the causal fungus was identified as Microstroma juglandis. The sequence of ITS rDNA of the present isolate showed 100% similarity with those of M. juglandis obtained from GenBank databases, thus confirming its identity. Pathogenicity tests were conducted on leaves of walnut seedlings, fulfilling Koch's postulates. The disease has been previously reported in North America, Europe, Oceania and some western Asia. This is the first report of downy leaf spot on walnuts in East Asia.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2018.10a
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• pp.38-38
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• 2018

최근 호두 기내 소비량은 급증하나 대부분 실생묘로 조림되어 결실까지 장기간 소요되며, 무성 번식률이 낮아 보급확대가 어렵다. 본 연구는 호두나무 관행 묘목 번식법 개선이 가능한 우량 국산묘 대량증식 기술 개발로 최적 배양조건을 구명하고자 수행하였디. 호두나무 등 목본류는 식물 조직배양 기본배지에서 산화방지제를 첨가하여 사용하는 경우, 배양체에서 생기는 페놀 화합물(Phenolic compound)의 작용을 억제하여 배양 식물체의 갈변(Browning) 또는 흑변(Blackening) 현상을 감소시키는 효과가 있다. 페놀 추출물은 배지로 빠져나와 갈변시키며 생존율을 저하시키는 원인이 되고 이를 제거하는 산화방지제는 배양 식물체의 생산효율을 높이는 효과를 나타내는 강력한 항산화제(Antioxidant) 역할을 한다. 호두나무의 액아를 배양하게 되면 조직 및 배지의 갈변화가 심하게 일어나는데, 휴면 정도가 깊을 수록 정단에서 추출되는 페놀성 물질의 함량이 증가하며, 식물 조직 내 페놀성 물질의 함량 정도와 배양의 고사율과는 상관관계가 있다. 이러한 식물 배양체에서 생기는 페놀 화합물에 의해 발생되는 배양상의 문제점을 해결하기 위하여 계대배양을 자주해 주거나 활성탄(Activated charcoal), Ascorbic Acid 등의 첨가물을 배지에 추가하는 방법이 있다. 이에 따라 호두 '신령' 품종의 액아배양의 페놀집적을 제거하기 위해 배지 내에 산화방지제 첨가물질 등을 농도별로 처리하였다. 호두나무 액아 배양 후 8주차 산화화방지제 첨가물질의 농도별 처리 효과는 생존율은 85.3%를 보였으며, 신초 형성율 76.4%, 신초수 1.9개/주, 신초장 27mm/주의 양호한 결과를 나타냈으며, 페놀 제거 및 유식물체 고사 억제 효과를 보였다.

• Korean journal of applied entomology
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• v.50 no.3
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• pp.253-256
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• 2011

The walnut leaf beetle, Gastrolina depressa, belongs to family Chrysomelidae (Coleoptera), and is one of the major pests of walnut trees. G. depressa eggs were oval and dark orange. The three G. depressa larval instars were gray in color. The larval period was approx. 8.14 days ($24^{\circ}C$, 16L:8D). Adults of both sexes were dark blue, and females were larger than males. Overwintered adults emerged in late April, and laid eggs in clusters on young leaves of the host tree. Mature 3rd instar larvae pupated after a short prepupal period. Adults emerged starting mid-May and entered into diapause shortly afterward.

• Korean journal of applied entomology
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• v.56 no.2
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• pp.121-133
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• 2017

This study was conducted to investigate the community structure of arthropods, including various insect pests and their natural enemies, in walnut orchards. Furthermore, we tried to compare the species richness and community structure of arthropods by three different sampling methods, including beating, funnel trap, and pitfall trap. Arthropods were surveyed in three walnut orchards located at Gimcheon, Buyeo, and Hwaseong in South Korea from May to September, 2016. A total of 408 arthropod species were identified from 4,372 individuals, and 63 species were collected in all study sites. The species richness was the highest in funnel trap, while the abundance was the highest in pitfall trap. The species composition of the insects collected by the beating method was more similar to that of the funnel trap than the pitfall trap. Although the distributions of the economically important pests were different according to the study sites, six species, including Dichocrocis punctiferalis, Pseudaulacaspis pentagona, Gastrolina depressa, Lycorma delicatula, Metcalfa pruinosa, and Pochazia shantungensis, are the potentially important pests in walnut orchards. We also found a variety of predators and parasitoids, which will be important for walnut pest management.

• Journal of Korean Society of Forest Science
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• v.109 no.3
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• pp.325-332
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• 2020

This study was conducted on cultivation farms in the Gimcheon area, which is the main production area of walnuts, in order to compare and analyze the yield and fruit quality of walnut trees (Juglans sinensis Dode) derived from seedlings. The official trees were classified into nine classes from 10 to 60 years old, and a total of 135 trees were selected, with 15 trees selected for each grade. The growth and fruit characteristics for each age group were then examined. The average tree height was 10.3 m, and the average crown area was 63.7 ㎡. The average number of fruit settings per tree was 573.1, with the largest number of walnuts per tree at 35 years (974.0 walnuts), and the lowest walnuts per tree at 10 years (124.7 walnuts). In addition, the number of fruit settings per bearing mother branch in 35 year old trees was the highest at 3.1. The average weight for each fruit type was found to be 58.7 ± 4.0 g of walnuts in green peel, 10.5 ± 0.5 g of dried shell walnuts, and 4.9 ± 0.2 g of walnuts, respectively. The average yield by fruit type was 32.5 ± 13.8 kg of walnuts in green peel, 5.9 ± 2.5 kg of dried shell walnut, and 2.8 ± 1.2 kg of walnuts. The yield was positively correlated with the crown area, the number of fruits setting per bearing mother branch, and the number of fruits setting per 1 ㎥. The formula used to estimate the yield per tree by age was calculated as y = 8993.9 ln (tree age-9) 8230.3, R² = 0.8531 (walnut in green peel) and y = 1647.1 ln (tree age-9) 1442.1, R² = 0.8527 (dried shell walnut).

• Korean journal of applied entomology
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• v.57 no.1
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• pp.33-38
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• 2018

Walnuts are one of the most economically important fruit trees in forestry. In walnut orchards, however, studies examining damage by insect pests are limited. This study was conducted to investigate the rate of damage caused by Conogethes punctiferalis to walnut fruits and by Acrocercops transecta to walnut leaves. In 2017, the change of damage rate (caused by C. punctiferalis) to fruits were investigated in Buyeo. In addition, we counted fruits and leaves damaged by two lepidopteran species in Gimcheon, Buyeo, Yeongdong, and Hwaseong. Damaged fruits steadily increased in abundance with fruit growth in Buyeo, and the highest number of damaged fruits was documented in late summer. The rates of damage caused by C. punctiferalis to fruits in Buyeo, Gimcheon, and Hwaseong were 22.1%, 20.5%, and 11.7%, respectively. Additionally, the rates of damage caused by A. transecta to leaves in seedlings (58.5% on average) were significantly higher than to those in older trees (11.2% on average), irrespective of the study location. In conclusion, this study showed that C. punctiferalis and A. transecta were serious pests affecting walnut fruits and leaves, respectively. Therefore, management methods for these insect pests need to be developed.

• Journal of Korean Society of Forest Science
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• v.99 no.4
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• pp.611-617
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• 2010

The current studies aim is to analyze the production cost of walnut tree cultivation and its object was targeted at walnut tree cultivating household region 163. The analysis is as follows. Our domestic walnut tree cultivating households averagely have cultivated about 0.7ha, and planting number per ha was averagely 204, and it showed that compared to the standard planting number (100), the plantation was done close planted. The most cultivar cultivated according to regions were Chungbuk region: sangchon 65.7%, Chungnam region: kwangduk 68.6%, Jeonbuk region: sangchon 98.0%, Gyeongbuk region: daeboo 61.2%. The production cost for cultivating walnuts can be classified into the followings; management cost(4436 thousand won/ha) such as manufacturing cost(292 thousand won/ha), intermediate material cost(3682 thousand won/ha), rent(103 thousand won/ha), employment cost(653 thousand won/ha) etc, and self-serviced expenses such as self-laboring cost(5,834 thousand won/ha), land security cost(490 thousand won/ha), fixed capital cost(834 thousand won/ha), circulating capital cost(234 thousand won/ha) etc. 11,820 thousand won were invested for the production cost of walnut and it made 11,586 thousand won/ha(rate of investment 72.3%) profit, and the net income was 4,196 thousand won/ha(net income rate 26.2%), showing high amount of income. The manufactured walnuts were marketed in Nong-hyup 39.8%, wholesalers 20.8%, dealers 19.8% and recently, as the amount of goods marketed directly to consumers themselves have increased, the income has reached up to 18.9%. At the basis of making most of idle soil, walnut tree's cultivated regions are fairly small, and due to the characteristics of sideline management, it has its limits in searching for production policy locally and promotion strategy of industries. Therefore, if the basic database can be established, subjected only to full-time cultivating households, then not only would the differences between the imported walnuts be reinforced, it would also be possible to transfer into the new and improved distribution system. Furthermore, through establishment of the database, it can be anticipated that it would contribute greatly in the increase of the household income.

• Korean journal of applied entomology
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• v.36 no.2
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• pp.156-165
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• 1997

Host plants and host preference of brown chafer, Adoretus tenuimaculatus Waterhouse (Coleoptera: Scarabaeidae) were investigated in fields and laboratory. 66 kinds of plants in 25 fanlilies were recorded as host during the field survey and 14 kinds in 5 families were verified to be eaten by artificial plant supply. Thus, host plants of A. tertuimaculatus were 186 kinds in 42 families in total including 136 kinds of plants in 32 families from literatures. 50 plants in 19 families were newly recorded as host of A. tenuimaculatus in this study. A. tenuimaculatus was the most frequently visited to J14glans sinensis and Caztanea crenata was the highest damaged plant. C. crenata, Robinia pseudoacasia, Malus sieboldii, J. sinensis, Quercus mongolica, and Q. aliena were considerably highly preferered host plant. However, A. tenuimaculatus never visited to Diospyros lotus, J. nigra, Fraxinus mandshurica, F. rhynchophylla, Pyracantha angustqolia, Paulownia coreana, and Celtis sinensis. Even the same host plant of A. tenuimaculatus. preference was different according to observed place and damage level was also different depending on observed place and time.