Pine wilt disease (PWD), caused by the pine wood nematode (Bursaphelenchus xylophilus), is a major threat to Pinus thunbergii forests in South Korea. Although climatic conditions are known to affect the spread of PWD, the specific influences of temperature and geography on nematode density and tree mortality remain unclear. This study assessed monthly PWN density and black pine mortality across three regions—two coastal (Geoje and Sacheon) and one inland (Jinju)—from 2021 to 2023. Nematode density and tree mortality consistently peaked in autumn across all regions. A strong positive correlation was observed between nematode density and tree mortality (r = 0.7468, p < 0.01), while temperature showed no significant correlation with either variable. These results indicate that PWD severity is more closely tied to nematode activity than to temperature alone, and that regional and seasonal variability must be considered in disease assessment. The findings highlight the need for region-specific monitoring and management strategies that prioritize high-risk periods, particularly autumn, when nematode activity and disease expression are most pronounced. This research provides essential data to support adaptive PWD control programs under changing climatic conditions.

Abstract
Introduction
Materials and Methods
    1. Study site selection
    2. Meteorological conditions of the study sites
    3. Selection of tree species in study areas
    4. Distribution of pine wood nematodes in dead trees
    5. Mortality rate of black pine in pwd-affected areas
    6. Data analysis
Results and Discussion
    1. Density of nematodes in dead black pine trees
    2. Monthly density of pine wood nematodes
    3. Seasonal mortality rates of black pine by study site
    4. Comparison of monthly mortality rates of blackpine, pwn density, and average temperature
References

• Man Leung Ha(Lecturer, Division of Environmental and Forest Science, Gyeongsang National University, Jinju, 52725, Korea)
• Hyun Kim(Senior Researcher, Institute of Agriculture and Life Science, Gyeongsang National University, Jinju 52828, Korea, Associate Professor, Division of Environmental and Forest Science, Gyeongsang National University, Jinju 52725, Korea)
• Chong Kyu Lee(Professor, Division of Environmental Forest Science, Gyeongsang National University, Jinju, 52725, Korea) Corresponding author