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Dr. WON IL CHOI
National Institute of Forest Science, Korea

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0 Climate Change
0 Ecological Modeling
0 Entomology
0 Population Dynamics
0 forest pests

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Journal article
Published: 29 July 2021 in Forests
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It is essential to maintain the health of forests so that they are protected against a diverse range of stressors and show improved resilience. An area-based forest health map is required for efficient forest management on a national scale however, most national forest inventories are based on in-situ observations. This study examined methodologies to establish an area-based map on tree vitality grade using field survey data, particularly that containing information on several trees at one point. The forest health monitoring dataset of the Republic of Korea was used in combination with 37 satellite-based environmental predictors. Four methods were considered: Multinomial logistic regression (MLR), random forest classification (RF), indicator kriging (IK), and multi-model ensemble (MME) approaches using species distribution models. The MLR and RF produced biased results, whereby almost all regions were classified as first grade; the spatialization results of these methods were considered inappropriate for forest management. The maps produced using the IK and MME methods improved the distinctions between the distributions of five grades compared to the previous two methodologies however, the MME method produced better results, reliably reflecting topographical and climatic characteristics. Comparisons with the vegetation condition index and bioclimate vulnerability index also emphasized the usefulness of the MME. This study is particularly relevant to the national forest managers who struggle to find the most effective forest monitoring and management strategies. Suggestions to improve spatialization of field survey data are further discussed.

ACS Style

Yuyoung Choi; Hye Chung; Chul-Hee Lim; Jun-Hee Lee; Won Choi; Seong Jeon. Multi-Model Approaches to the Spatialization of Tree Vitality Surveys: Constructing a National Tree Vitality Map. Forests 2021, 12, 1009 .

AMA Style

Yuyoung Choi, Hye Chung, Chul-Hee Lim, Jun-Hee Lee, Won Choi, Seong Jeon. Multi-Model Approaches to the Spatialization of Tree Vitality Surveys: Constructing a National Tree Vitality Map. Forests. 2021; 12 (8):1009.

Chicago/Turabian Style

Yuyoung Choi; Hye Chung; Chul-Hee Lim; Jun-Hee Lee; Won Choi; Seong Jeon. 2021. "Multi-Model Approaches to the Spatialization of Tree Vitality Surveys: Constructing a National Tree Vitality Map." Forests 12, no. 8: 1009.

Communication
Published: 27 April 2021 in Forests
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We quantified the extent and severity of Asian gypsy moth (Lymantria dispar) defoliation in Wonju, Korea, from May to early June in 2020. Landsat images were collected covering Wonju and the surrounding area in June from 2017 to 2020. Forest damage was evaluated based on differences between the Normalized Difference Moisture Index (NDMI) from images acquired in 8 June 2020 and the prior mean NDMI estimated from images in June from 2017 to 2019. The values of NDMI ranged from −1 to 1, where values closer to 1 meant higher canopy cover. The NDMI values for 7825 ha of forests were reduced by more than 0.05 compared to the mean NDMI values for the prior 3 years (2017 to 2019). The NDMI values of 1350 ha of forests were reduced by >0.125 to 0.2, and the NDMI values for another 656 ha were reduced by more than 0.2. A field survey showed that these forests were defoliated by gypsy moth and that forests with NDMI reductions of more than 0.2 were heavily defoliated by gypsy moth. A 311 ha area of Japanese larch (Larix kaempferi) was severely damaged by gypsy moth and the proportion of larch damaged was higher than that of other tree species. This intense damage to larch suggests that gypsy moths preferentially attack Japanese larch in Wonju. Our study shows that the use of NDMI values to detect areas defoliated by gypsy moth from satellite images is effective and can be used to measure other characteristics of gypsy moth defoliation events, such as host preferences under field conditions.

ACS Style

Won-Il Choi; Eun-Sook Kim; Soon-Jin Yun; Jong-Hwan Lim; Ye-Eun Kim. Quantification of One-Year Gypsy Moth Defoliation Extent in Wonju, Korea, Using Landsat Satellite Images. Forests 2021, 12, 545 .

AMA Style

Won-Il Choi, Eun-Sook Kim, Soon-Jin Yun, Jong-Hwan Lim, Ye-Eun Kim. Quantification of One-Year Gypsy Moth Defoliation Extent in Wonju, Korea, Using Landsat Satellite Images. Forests. 2021; 12 (5):545.

Chicago/Turabian Style

Won-Il Choi; Eun-Sook Kim; Soon-Jin Yun; Jong-Hwan Lim; Ye-Eun Kim. 2021. "Quantification of One-Year Gypsy Moth Defoliation Extent in Wonju, Korea, Using Landsat Satellite Images." Forests 12, no. 5: 545.

Editorial
Published: 03 October 2019 in Forests
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Forest pests are one of the most important factors disturbing forest ecosystems, by impacting forestry economy, ecosystem services, biodiversity, and sustainable ecosystem management. Monitoring the occurrence of forest pests offers clues to understand their impacts on the forest ecosystem and develop a sustainable ecosystem management strategy. This special issue is designed to create a better understanding of the changes and impacts of forest pests according to forest changes, caused by natural or anthropogenic causes. There are 13 papers published in this special issue, covering several issues concerning forest pests. Two of the papers reviewed the changes in forest pests in Korea or Poland. The remaining twelve papers covered issues concerning the monitoring, assessment, and management of forest pests. Through this special issue, we expect to contribute towards the improvement of our knowledge of the structures and processes in forest ecosystems relating to forest pests and fundamental information for the effective management of forest pests.

ACS Style

Won Il Choi; Young-Seuk Park; Choi; Park. Monitoring, Assessment and Management of Forest Insect Pests and Diseases. Forests 2019, 10, 865 .

AMA Style

Won Il Choi, Young-Seuk Park, Choi, Park. Monitoring, Assessment and Management of Forest Insect Pests and Diseases. Forests. 2019; 10 (10):865.

Chicago/Turabian Style

Won Il Choi; Young-Seuk Park; Choi; Park. 2019. "Monitoring, Assessment and Management of Forest Insect Pests and Diseases." Forests 10, no. 10: 865.

Review
Published: 15 August 2019 in Forests
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Understanding the occurrence patterns of forest pests is fundamental for effective forest management from both economic and ecological perspectives. Here, we review the history of the occurrence patterns and causes of outbreaks and declines of pests in Korean pine forests over the last 50 years. During this period, the major pests of pine forests in Korea have shifted from pine caterpillar (Dendrolimus spectabilis Butler) to the pine needle gall midge (PNGM, Thecodiplosis japonensis (Uchida and Inouye)) and finally to pine wilt disease (PWD) caused by the pine wood nematode (Bursaphelenchus xylophilus (Steiner and Buhrer) Nickle). Outbreaks of pine caterpillar, a native species in Korea, have been recorded as far back as 900 years, and it was the most relevant forest pest in Korea until the 1970s. The decline of its importance has been attributed to reforestation and higher levels of subsequent natural enemy activity. The PNGM is an invasive species, first discovered in Korea in 1929, that became widely distributed by 1992 and the major forest pest in the 1980s and 1990s. A suite of parasitic wasps attacking the PNGM contributed at least partially to the decline of PNGM densities. Following the decline of the PNGM, damage from PWD has increased since 2003. These shifts in major forest pests might be related to changes in forest composition and interactions among forest pests. Therefore, a new management strategy for controlling forest pests is required to mitigate the decline of pine forests in Korea.

ACS Style

Won Il Choi; Youngwoo Nam; Cha Young Lee; Byoung Ki Choi; Yu Jin Shin; Jong-Hwan Lim; Sang-Hyun Koh; Young-Seuk Park. Changes in Major Insect Pests of Pine Forests in Korea Over the Last 50 Years. Forests 2019, 10, 692 .

AMA Style

Won Il Choi, Youngwoo Nam, Cha Young Lee, Byoung Ki Choi, Yu Jin Shin, Jong-Hwan Lim, Sang-Hyun Koh, Young-Seuk Park. Changes in Major Insect Pests of Pine Forests in Korea Over the Last 50 Years. Forests. 2019; 10 (8):692.

Chicago/Turabian Style

Won Il Choi; Youngwoo Nam; Cha Young Lee; Byoung Ki Choi; Yu Jin Shin; Jong-Hwan Lim; Sang-Hyun Koh; Young-Seuk Park. 2019. "Changes in Major Insect Pests of Pine Forests in Korea Over the Last 50 Years." Forests 10, no. 8: 692.

Journal article
Published: 01 January 2019 in Plant Disease
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ACS Style

C. H. Jeon; S. H. Kang; W. I. Choi; H. D. Shin. First Report of Powdery Mildew Caused by Podosphaera tridactyla on Prunus davidiana in Korea. Plant Disease 2019, 103, 158 -158.

AMA Style

C. H. Jeon, S. H. Kang, W. I. Choi, H. D. Shin. First Report of Powdery Mildew Caused by Podosphaera tridactyla on Prunus davidiana in Korea. Plant Disease. 2019; 103 (1):158-158.

Chicago/Turabian Style

C. H. Jeon; S. H. Kang; W. I. Choi; H. D. Shin. 2019. "First Report of Powdery Mildew Caused by Podosphaera tridactyla on Prunus davidiana in Korea." Plant Disease 103, no. 1: 158-158.

Research article
Published: 01 July 2018 in Plant Disease
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Hydrangea serrata f. acuminata (Siebold & Zucc.) E.H. Wilson (Hydrangeaceae) is a deciduous shrub growing in warm areas of Japan and Korea. Some horticultural varieties are widely cultivated as an attractive ornamental shrub throughout the world. In October 2016, several dozen of plants growing wild exhibited powdery mildew symptoms with 100% disease incidence in Jeju, Korea (33°28'12"N; 126°29'35"E). Powdery mildew colonies were circular to irregular, forming white patches on both sides of the leaves and stems. Severe infections caused purplish discolorations on the adaxial leaf surface. The same symptoms were observed in several localities in Jeju in 2017. Four voucher specimens were deposited in the Korea University Herbarium (KUS-F30146, F30186, F30190 and F30291). Chasmothecia were not observed during our survey. Appressoria were well-developed, single or in pairs, and lobed. Conidiophores were 85 to 145 × 7 to 10 µm, straight, and composed of 3 to 4 cells. Foot-cells were mostly not exceeding 30 µm long, short, and straight. Conidia were 35 to 48 × 16 to 21 µm with a length/width ratio of 1.8 to 2.7, solitary, oblong-elliptical to oblong, lacking distinct fibrosin bodies, and showed angular/rectangular wrinkling pattern of conidial outer walls. Conidial germ tubes were produced at the perihilar position. Primary conidia were generally smaller than secondary conidia, apically round, and basally sub-truncate. The morphological characteristics and host genus were consistent with those of Pseudoidium hortensiae (Jørst.) U. Braun & R.T.A. Cook (Braun and Cook 2012). To confirm the species identity using molecular analysis, the DNA of KUS-F30146 and F30186 were extracted and internal transcribed spacer (ITS) regions including 5.8S rDNA were amplified with primers ITS5/P3 described by Takamatsu et al. (2009), and sequenced directly. The obtained sequences were submitted to GenBank (Accession Nos. MG654731 and MG654732). A GenBank BLAST search of the two Korean isolates had a 100% sequence identity to Oidium hortensiae Jørst. (syn. Pseudoidium hortensiae) ex H. macrophylla (Thunb.) Ser. from Korea (e.g., JQ669944) and P. hortensiae ex H. macrophylla from Japan (e.g., LC009915). Pathogenicity was confirmed through inoculation by gently dusting conidia onto leaves of five healthy potted plants. Five non-inoculated plants served as controls. Inoculated plants developed symptoms after 10 days, whereas the control plants remained symptomless. The fungus present on the inoculated plants was identical in morphology to those observed in the field. Pseudoidium hortensiae has been recorded on more than 10 species and varieties of Hydrangea (Farr and Rossman 2017). Of those, P. hortenaise on H. serrata var. megacarpa was recorded in Japan (Meeboon and Takamatsu 2015). Therefore, this is the first report of powdery mildew caused by P. hortensiae on H. serrata f. acuminata globally as well as in Korea. The disease would be a serious threat to the widespread ornamental plantings of H. serrata f. acuminata in Korea, especially in Jeju Island.

ACS Style

S. E. Cho; T. T. Zhao; C. H. Jeon; S. H. Kang; W. I. Choi; H. D. Shin. First Report of Powdery Mildew Caused by Pseudoidium hortensiae on Hydrangea serrata f. acuminata in Korea. Plant Disease 2018, 102, 1453 -1453.

AMA Style

S. E. Cho, T. T. Zhao, C. H. Jeon, S. H. Kang, W. I. Choi, H. D. Shin. First Report of Powdery Mildew Caused by Pseudoidium hortensiae on Hydrangea serrata f. acuminata in Korea. Plant Disease. 2018; 102 (7):1453-1453.

Chicago/Turabian Style

S. E. Cho; T. T. Zhao; C. H. Jeon; S. H. Kang; W. I. Choi; H. D. Shin. 2018. "First Report of Powdery Mildew Caused by Pseudoidium hortensiae on Hydrangea serrata f. acuminata in Korea." Plant Disease 102, no. 7: 1453-1453.

Journal article
Published: 30 October 2017 in Forests
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We characterized the dispersal patterns of pine wilt disease (PWD) in the early stage of its invasion in the South Korea, and estimated the influence of environmental factors on the dispersal of PWD. Data were obtained in 10 regions with at least five consecutive years of data for 10 years from 1994 to 2005. The dispersal patterns of PWD were categorized into four types: type 1 is a jumping type of dispersal, forming new patches; type 2 infestations are ones without any expansion of patch size; and types 3 and 4, respectively, show uni-directional or multi-directional dispersal outward from an existing patch. Dispersal patterns changed during different phases of the pathogen’s invasion history: type 1 was the most frequent in the early invasion stage. Annual dispersal distance showed regional variations. Human population density had a positive correlation with the dispersal distance of PWD, indicating that anthropogenic factors can contribute to the dispersal of PWD. Our results suggested that dispersal through jumping from areas occupied by PWD was the main dispersal route in the early stage of invasion and that after this phase, the existing colonies expanded and merged. These results supported the existence of stratified dispersal patterns of PWD.

ACS Style

Won Il Choi; Hye Jung Song; Dong Soo Kim; Dae-Sung Lee; Cha-Young Lee; Youngwoo Nam; Joon-Bum Kim; Young-Seuk Park. Dispersal Patterns of Pine Wilt Disease in the Early Stage of Its Invasion in South Korea. Forests 2017, 8, 411 .

AMA Style

Won Il Choi, Hye Jung Song, Dong Soo Kim, Dae-Sung Lee, Cha-Young Lee, Youngwoo Nam, Joon-Bum Kim, Young-Seuk Park. Dispersal Patterns of Pine Wilt Disease in the Early Stage of Its Invasion in South Korea. Forests. 2017; 8 (11):411.

Chicago/Turabian Style

Won Il Choi; Hye Jung Song; Dong Soo Kim; Dae-Sung Lee; Cha-Young Lee; Youngwoo Nam; Joon-Bum Kim; Young-Seuk Park. 2017. "Dispersal Patterns of Pine Wilt Disease in the Early Stage of Its Invasion in South Korea." Forests 8, no. 11: 411.

Journal article
Published: 17 May 2015 in Journal of Economic Entomology
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Monochamus saltuarius Gebler is a vector that transmits the pine wood nematode, Bursaphelenchus xylophilus, to Korean white pine, Pinus koraiensis, in Korea. To reduce the damage caused by this nematode in pine forests, timely control measures are needed to suppress the cerambycid beetle population. This study sought to construct a forecasting model to predict beetle emergence based on spring temperature. Logs of Korean white pine were infested with M. saltuarius in 2009, and the infested logs were overwintered. In February 2010, infested logs were then moved into incubators held at constant temperature conditions of 16, 20, 23, 25, 27, 30 or 34°C until all adults had emerged. The developmental rate of the beetles was estimated by linear and nonlinear equations and a forecasting model for emergence of the beetle was constructed by pooling data based on normalized developmental rate. The lower threshold temperature for development was 8.3°C. The forecasting model relatively well predicted the emergence pattern of M. saltuarius collected from four areas in northern Republic of Korea. The median emergence dates predicted by the model were 2.2–5.9 d earlier than the observed median dates.

ACS Style

Chan Sik Jung; Sang-Hyun Koh; Youngwoo Nam; Jeong Joon Ahn; Cha Young Lee; Won Il Choi. A Model for Predicting Spring Emergence ofMonochamus saltuarius(Coleoptera: Cerambycidae) from Korean white pine,Pinus koraiensis. Journal of Economic Entomology 2015, 108, 1830 -1836.

AMA Style

Chan Sik Jung, Sang-Hyun Koh, Youngwoo Nam, Jeong Joon Ahn, Cha Young Lee, Won Il Choi. A Model for Predicting Spring Emergence ofMonochamus saltuarius(Coleoptera: Cerambycidae) from Korean white pine,Pinus koraiensis. Journal of Economic Entomology. 2015; 108 (4):1830-1836.

Chicago/Turabian Style

Chan Sik Jung; Sang-Hyun Koh; Youngwoo Nam; Jeong Joon Ahn; Cha Young Lee; Won Il Choi. 2015. "A Model for Predicting Spring Emergence ofMonochamus saltuarius(Coleoptera: Cerambycidae) from Korean white pine,Pinus koraiensis." Journal of Economic Entomology 108, no. 4: 1830-1836.