Effect of the Cut Lengths of Damaged Logs and Left On-site Forests on the Number of Newly Emerged Adults, the Oak Platypodid Beetle Platypus quercivorus

Abstract

Japanese oak wilt is an infectious tree disease transmitted by the oak platypodid beetle, Platypus quercivorus. One of the most effective methods to prevent the spread of the disease is to remove infected trees from forests; however, this requires significant on-site efforts. In this study, we evaluated the possibility of reducing the number of newly emerged adults by leaving short logs of varying lengths in the study area. We cut trees affected by the beetles and collected logs of three different lengths (100, 30, and 15 cm), which were left on-site until May 2023. The logs were placed into traps to capture adults, and collections were made monthly in June, July, August, and November 2023. The number of adults per volume collected from the 30 and 15 cm logs was significantly lower than that from the 100 cm logs. While many adults emerged from the 100 cm logs in June and July, few individuals were found in the shorter logs during the subsequent collection months. Our results suggest that leaving short logs (less than 30 cm) in forests could be an effective strategy for managing oak wilt, while reducing the high on-site efforts required to remove infected trees.