Rapid spread and high prevalence of the pine wilt disease around wildfire areas

Abstract

Pine trees hold a vital position in South Korea's forests, yet they face significant threats due to the spread of pine wilt disease. Pine Wilt Disease (PWD) is a devastating condition that causes rapid wilting and eventual death in susceptible pine trees. Notably, given the life cycle characteristics of the pine wood nematode and its Monochamus beetle vectors, concerns are growing that wildfire-affected areas may accelerate the spread of pine wilt disease. Therefore, the objective of this study is to analyze changes in the spatial distribution of pine wilt disease before and after wildfires using inspection data and to evaluate the relative risk of infection detection rates in wildfire-affected areas. To achieve this, we analyzed data from 2016 to 2023 in Goryeong-gun, Gyeongsangbuk-do, South Korea. At the administrative district level, Global Moran's I and Local Indicators of Spatial Association (LISA) were employed, and detailed cluster analysis was conducted using SaTScan software for the post-wildfire period. The analysis revealed that clusters were formed in pre-existing outbreak areas before the wildfire, while newly significant clusters emerged around wildfire-affected areas after the wildfire. Subsequently, the standardized relative risk between wildfire-affected and non-affected areas was analyzed to quantify the difference in risk levels. The analysis indicated that wildfire-affected areas, particularly Sinchon-ri in Ssangnim-myeon, Goryeong-gun, exhibited a significantly higher relative risk of 1.87 (95 % confidence interval [CI]: 1.57–2.10). To our knowledge, this study is the first attempt to observe an increased risk of pine wilt disease spread in and around wildfire-affected areas. The findings suggest that when wildfires occur, intensified control measures should be implemented not only in directly affected areas but also in surrounding regions to effectively manage pine wilt disease.