Incidence of pine needle blight and its relationship with site factors of Japanese red pine forests in the Kunyushan Mountains, East China

Abstract

Pine needle blight (Pestalotiopsis funerea (Desm.) Steyaert) has caused major damage to the Japanese red pine (JRP, Pinus densiflora Sieb. et Zucc.) forests in the Kunyushan Mountains region (121°41′34″–121°48′04″ E, 37°11′50″–37°17′22″ N) of Shandong, China. Site factors play an important role in the occurrence of JRP needle blight. Here, the regression equations of the disease incidence (DI) site factors and disease severity index (DSI) site factors were established to predict the incidence and severity of JRP needle blight. In this study, the site factors, DI, and DSI of pine needle blight were surveyed in 121 pure JRP forests plots. The incidence and severity of JRP needle blight were investigated, and regression equations were developed for DI and DSI site factors. The results show that JRP needle blight was a common disease in the Kunyushan Mountains, and 95.9% of the surveyed plots were affected. The DI and DSI of JRP needle blight were significantly affected by altitude, slope angle, and humus depth (p < 0.05), as well as highly significantly affected by slope shape and slope aspect (p < 0.01). The R2 values of DI and DSI models were 0.68 and 0.798, respectively, indicating that their interpretation rate for the occurrence of JRP needle blight is more than 65%, proving that the model is reliable and that key site factors can be used to predict the incidence of JRP needle blight. Overall, the occurrence of pine needle blight in forest land with low altitude, steep and shaded slopes, and thinner humus depth was higher than in other types of sample plots. Thus, the prevention of JRP needle blight should be the focus in this type of woodland.