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BACKGROUND: Pine wilt disease (PWD), a major international quarantined forest pest, causes serious ecological and economic damage to Pinus species in Asia and Europe. In China, PWD has spread northeasterly and northwesterly beyond its original northern limits. Consequently, an evaluation of the insect vector‐mediated occurrence and potential diffusion of PWD is needed to identify important transmission routes and control the spread of disease. RESULTS: An optimized MaxEnt model was used to assess the current and future geographical distribution of Bursaphelenchus xylophilus and its insect vectors in China. The predicted suitable area for B. xylophilus colonization is currently 212.32 × 104 km2 and mainly concentrated in Central, East, Southwest and South China, although is anticipated to include the northwestern regions of China in the future. As for the insect vectors, Monochamus alternatus and M. saltuarius are expected to spread toward the northwest and southwest, respectively. The maximum predicted dispersion area of PWD mediated by M. alternatus, M. saltuarius and both species was 91.85 × 104, 218.76 × 104 and 29.99 × 104 km2, respectively, with potential diffusion areas being anticipated to increase in the future. Both the suitable probabilities and areas of B. xylophilus and its insect vectors were found to vary substantially along the latitudinal gradient, with the latitudinal range of these species being predicted to expand in the future. CONCLUSION: This is the first study to investigate the potential diffusion areas of PWD mediated by insect vectors in China, and our finding will provide a vital theoretical reference and empirical basis for developing more effective management strategies for the control of PWD in China. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Masson pine stands infected by Pine wilt disease (PWD) in the Three Gorges Reservoir Region of central China were surveyed to quantify the immediate responses and subsequent trajectories of biomass, carbon (C), and nitrogen (N) in stand-level major ecosystem compartments. The biomasses of above- and belowground tree components, as well as of the understory, forest floor, and mineral soil (0–40 cm), were determined within each stand. C and N storage were also estimated for each ecosystem compartment. Overstory biomass decreased steadily with the extent of PWD infection. Understory biomass ranged from 1.97 to 4.16 Mg ha−1, and the observed value for forest floor biomass was 12.89–22.59 Mg ha−1. The highest mean C and N concentrations were found in the stem bark and needles of Masson pine, respectively, while the lowest were found in the semi- to fully decomposed layer of the forest floor and stem wood of Masson pine, respectively. The C and N storage of aboveground trees, tree roots, and the aboveground ecosystem decreased with the extent of PWD infection. However, the C and N contents of the understory, forest floor, and total mineral soil initially declined after PWD infection before recovering over the following several years. Those result concluded that the biomass, C, and N storage of different forest ecosystem compartments have experienced certain variations following the PWD epidemic. This is vital to understand the shifts in stand-level C and N allocation in PWD-damaged forest stands, as well as for predicting the responses of regional and global C and N cycling. [ABSTRACT FROM AUTHOR]

Pine wilt disease ( PWD) is considered as the most destructive forest-invasive alien species in China. We measured gas exchange parameters and foliar carbon isotope ratios (δ13C) of different infection phases of Masson pine in order to investigate the effect of Bursaphelenchus xylophilus infection on photosynthetic responses and resource-use efficiency. The results showed that net photosynthetic rate ( Pn), transpiration rate ( T), stomatal conductance ( gs), and internal CO2 concentrations ( Ci) decreased in the infested trees at photosynthetic photon flux density ( PPFD) levels from 0 to 2,000 μmol m−2 s−1 compared with controls. The maximum net photosynthetic rate ( Pmax) was significantly declined in the infected trees than in controls ( p < .05). There also exist significant differences in dark respiration rate ( Rd) among different infection phases ( p < .05), but the value is highest in the middle infection phase, followed by the control and then the terminal infection phase. This indicates that Pinus massoniana plants need to consume more photosynthetic products during the middle infection phase in order to defend against pine sawyer beetle feeding and PWD infection. Isotopic analysis revealed a significant decrease of the foliar δ13C ( p < .05), as much as 2.5‰ lower in the infected trees. The mean leaf N content was about 12.94% less in the middle infection phase and 27.06% less in the terminal infection phase, causing a significant increase of the foliar C:N ratio in infested trees. Both of the net photosynthetic rates and foliar δ13C were linearly correlated with the foliar N content. We also found a significant decrease ( p < .05) of resource-use efficiency in PWD-induced P. massoniana plants, which can be attributed to the closure of stomatal pores and the inactivation or loss of both Rubisco and other key Calvin cycle enzymes. This study highlights the impact of photosynthetic characteristics, foliar carbon isotope ratios, and resource-use efficiency of PWD-induced trees, which can help identify PWD infestations at the photosynthetic and physiological levels so as to better facilitate management actions. [ABSTRACT FROM AUTHOR]