This study explored the application of carbon stable isotopes for tracing the geographical origin of Monochamus alternatus, an insect vector responsible for spreading pine wilt disease. The primary vector of pine wilt disease, an aggressive disease caused by the pine wood nematode and affecting pine forests, is Monochamus alternatus. Samples of Monochamus alternatus were collected from 12 provinces across China, and their carbon isotope ratios (δ¹³C) were measured. By analyzing the correlation between these ratios and various environmental factors, including latitude, longitude, altitude, and bioclimatic conditions, it was found that precipitation seasonality and solar radiation were the most important factors influencing the carbon isotope ratio of Monochamus alternatus. The spatial distribution of Monochamus alternatus carbon isotopes in China was predicted using the co-Kriging interpolation method, incorporating these two environmental variables. The findings revealed a gradient in the carbon isotope ratio of Monochamus alternatus, which could help differentiate the species across various geographical regions in China.

Obolodiplosis robiniae (Haldeman) is a specialist herbivore of Robinia pseudoacacia L., and its infestation is closely associated with tender leaf tissues. The ability of gravid females to recognize suitable host tissues is essential for successful oviposition and subsequent population development. Here, we assessed whether leaf age affects the host-selection behavior of O. robiniae and whether volatile organic compounds are associated with this process. Laboratory oviposition assays were used to compare egg deposition on tender leaves and mature leaves of R. pseudoacacia, and Y-tube olfactometer bioassays were performed to evaluate female responses to odors from the two leaf ages. Volatiles released from healthy tender leaves and mature leaves were collected using dynamic headspace sampling and characterized by thermal desorption–gas chromatography–mass spectrometry. Principal component analysis, orthogonal partial least squares discriminant analysis, and variable importance in projection scores were used to compare volatile profiles between leaf ages. Gravid females deposited significantly more eggs on tender leaves than on mature leaves in both choice and no-choice assays. Females also showed a significant olfactory preference for tender-leaf odors when directly offered a choice between volatiles from tender leaves and mature leaves, with 76.47% of responding individuals selecting tender-leaf odors and 23.53% selecting mature-leaf odors. Chemical profiling identified 28 volatile compounds across the two leaf ages, and their composition and relative abundance differed markedly. Among shared compounds, (Z)-3-hexen-1-ol and α-farnesene differed significantly between tender leaves and mature leaves. Multivariate analyses further identified several candidate compounds contributing to leaf age-related volatile differences. These results indicate that leaf age influences both oviposition behavior and odor-mediated host location in O. robiniae. Leaf age-dependent volatile blends may serve as important chemical cues associated with host selection by gravid females and provide a basis for future studies on volatile-mediated management strategies.

A major challenge in invasive species management is the detection lag between species introduction and the official first record, during which undetected populations can spread unchecked. Citizen science records may theoretically provide earlier warning signals, yet whether they are as effective for taxonomically challenging groups such as invasive forest wood-boring pests, which often require specialist identification, as they are for more easily identifiable taxa, remains poorly evaluated. This study examined 20 invasive forest wood-boring pests and integrated citizen science records with official records to construct a dual-scale spatiotemporal comparison framework at the country level across nations and at the municipal scale in China. We collected 129 official first records from 49 countries, and after filtering for record completeness and reliability, retained 14,889 citizen science records. Among the 79 matched species–country pairs, citizen science records showed a strong positive lag, with only 2.5% preceding official records and 3.8% occurring in the same year. Although the mean time lag decreased from 24.82 years overall to 5.18 years in the post-2010 subset, positive lags remained dominant. Citizen science recording intensity was significantly influenced by adult detectability, a composite trait based on adult body size and adult body coloration ( p = 0.010). At the municipal scale in China, we compiled 36 official species–city records across 11 provinces for invasive pests. Citizen science records supplemented spatial information but were absent for H. ligniperda and S. noctilio . Overall, for invasive forest wood-boring pests, the value of citizen science lies more in expanding spatial surveillance and tracking subsequent spread than in consistently shortening time lag.