Hylurgus ligniperda is a major international quarantine pest, native to the southern Mediterranean coast of Europe and northern Africa, and causes significant damage in invaded areas. In 2020, it was first confirmed to be established and causing harm in Yantai City, Shandong Province, China, primarily infesting Japanese black pine (Pinus thunbergii). Owing to environmental and climatic differences, the biological and ecological traits of this new invasive pest may undergo changes in newly colonized regions, potentially diverging from those observed in its native range. This study aimed to elucidate the biological characteristics of H. ligniperda in its newly invaded range. Based on the establishment of artificial breeding techniques for this pest, this study combined field dissections with multiple indoor rearing methods, to investigate its biological characteristics in Yantai, Shandong Province. A simple and efficient artificial breeding method was developed using phloem bark powder and purified water. The study confirmed that H. ligniperda completes three generations annually in Yantai. The first generation emerges from overwintering adults in early May, with mass adult dispersal observed. May and June represent the peak period for oviposition and larval emergence. The second generation oviposits in July and August, and even after the third generation emerges in September, some adults continue to lay eggs. H. ligniperda primarily overwinters as adults and larvae, exhibiting overlapping generations. Observations of external morphological traits and ovary dissections revealed that the coloration of both male and female adults changes with age post-emergence: approximately 15 days after emergence, their color transitions from yellowish-white to reddish-brown, then to brown, and finally to black. Females reach sexual maturity around 10 days after emergence. This study preliminarily elucidates the life cycle, growth, and developmental duration of H. ligniperda in the invaded region, providing a theoretical foundation for effective management and containment of its further spread.

Pinus thunbergii is one of the main species in the coastal protection forests of the Jiaodong Peninsula, China. The large-scale damage caused by the invasive species Hylurgus ligniperda has seriously affected the quality of the coastal protection forests in the Jiaodong Peninsula. This study aimed to understand the changes in metabolites and volatiles in the root systems of P. thunbergii infested by H. ligniperda. Rhizosphere soils of P. thunbergii under healthy, early-stage infestation, and late-stage infestation states were collected. Additionally, volatiles of root system were collected from healthy P. thunbergii, those in the early and late stages of H. ligniperda infestation, and those with mechanical damage using the static headspace adsorption. Ultra-high-performance liquid chromatography-mass spectrometry (UPLC-MS) and gas chromatography-mass spectrometry (GC-MS) were used to analyze rhizosphere metabolites and root volatiles, respectively. The main results are as follows: a total of 1183 metabolites were detected in the rhizosphere of P. thunbergii, among which lipids and their derivatives accounted for the largest proportion (25.87%). Rhizosphere metabolites differed among groups at different infestation stages. Compared with healthy P. thunbergii, those at the early-stage infestation showed 21 significantly differential metabolites (VIP > 1, |Log2FC| > 1, P < 0.05), including aristolone, nootkatone, ubiquinone Q2, and phosphatidylserine. In comparison with the late infestation stage, there were 24 significantly differential metabolites. The contents of soluble sugars (such as galactose, glucose, and mannose) initially decreased and then increased with the severity of H. ligniperda infestation. Thirty volatile compounds were detected in the roots of P. thunbergii, with 24, 29, and 23 volatile compounds identified in healthy roots, pest-infested roots and mechanically damaged roots, respectively. The relative content of (1R)-(+)-α-pinene was the highest, accounting for 48.21%, 56.88%, 62.77% and 58.06% in the healthy (H), early-infested (Y), late-infested (D) and mechanically damaged (J) groups, respectively. The relative contents of (1R)-(+)-α-pinene, D-limonene, (-)-β-pinene, camphene, and α-phellandrene increased in the early stage of pest infestation. However, only (1R)-(+)-α-pinene and camphene showed a continuous increase in the late stage. Additionally, camphene, as a pest-specific volatiles, decreased after mechanical damage. D-camphor (natural), borneol, 4-etheny-1,2-dimethylbenzene, fenchol, α-terpineol, and 1,8-eucalyptol were detected only in the group infested by H. ligniperda, but not in the healthy group or the mechanically damaged group. The results showed that at the early stage of H. ligniperda infestation, P. thunbergii could resist the infestation by increasing stress-resistant components such as aristolone, nootkatone, (1R)-(+)-α-pinene, D-limonene and camphene, while decreasing soluble sugar content. At the later stage of infestation, dying pines reduced stress-resistant components and increased soluble sugar content. This study revealed that nootkatone can be exploited for the development of natural derivative insecticides, while camphene holds potential for the creation of novel plant-derived attractants. These findings lay a theoretical foundation for in-depth investigations into infestation mechanisms and the development of green, efficient pest control technologies.