Climatic and Geographic Influences on Seasonal Nematode Density and Pine Wilt Disease Mortality Author Names

Abstract

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.