Elaeagnus angustifolia L. can attract adult Asian longhorned beetle (ALB), Anoplophora glabripennis (Motschulsky), and kill their offspring by gum secretion in oviposition scars. This plant has the potential to be used as a dead-end trap tree for ALB management. However, there is a limited understanding of the attraction ability and biochemical defense response of E. angustifolia to ALB. In this study, we conducted host selection experiments with ALB and then performed physiological and biochemical assays on twigs from different tree species before and after ALB feeding. We analyzed the differential metabolites using the liquid chromatograph–mass spectrometer method. The results showed that ALB’s feeding preference was E. angustifolia > P.× xiaohei var. gansuensis > P. alba var. pyramidalis. After ALB feeding, the content of soluble sugars, soluble proteins, flavonoids, and tannins decreased significantly in all species. In three comparison groups, a total of 492 differential metabolites were identified (E. angustifolia:195, P.× xiaohei var. gansuensis:255, P. alba var. pyramidalis:244). Differential metabolites were divided into overlapping and specific metabolites for analysis. The overlapping differential metabolites 7-isojasmonic acid, zerumbone, and salicin in the twigs of three tree species showed upregulation after ALB feeding. The specific metabolites silibinin, catechin, and geniposide, in E. angustifolia, significantly increased after being damaged. Differential metabolites enriched in KEGG pathways indicated that ALB feeding activated tyrosine metabolism and the biosynthesis of phenylpropanoids in three tree species, with a particularly high enrichment of differential metabolites in the flavonoid biosynthesis pathway in E. angustifolia. This study provides the metabolic defense strategies of different tree species against ALB feeding and proposes candidate metabolites that can serve as metabolic biomarkers, potentially offering valuable insights into using E. angustifolia as a control measure against ALB.

Ecological control studies of the Asian longhorned beetle (Anoplophora glabripennis) distinguish susceptible, resistant, and dead-end trap trees as functionally different plant categories. We used shotgun metagenomics to examine bacterial and archaeal profiles detected in adult gut samples after 72 h exposure to three dietary plants or prolonged water-only starvation. The study included 24 metagenomes, with three biological replicates per DietGroup × SexGroup combination. No time-zero gut samples were available, so the observed patterns remain superimposed on the beetles’ field history. The retained catalogue contained 152,895 bacterial genes and 9 archaeal genes. The original observed-richness difference was strongly correlated with host-depleted read depth and was not supported after common-depth rarefaction. Genus-level Bray–Curtis analysis detected a DietGroup × SexGroup interaction that persisted after depth adjustment and exclusion of low-yield samples. This interaction was exploratory because of the small within-cell sample size. Raw Bray–Curtis analysis of KEGG Orthology profiles showed a DietGroup association, but this association was not robust to direct-depth adjustment or Aitchison analysis. CAZy profiles were descriptive and showed no significant DietGroup effect. These results indicate short-term, depth-sensitive associations between dietary treatment and gut-sample bacterial and archaeal profiles. They do not establish resident status, microbial activity, or a physiological mechanism.