Gut microbial symbionts are increasingly recognized as key modulators of host insect physiology and behavior, yet their role in pheromone-mediated chemical communication remains insufficiently understood. In this study, we investigated the wood-boring beetle Trigonorhinus sp., a pest of Caragana liouana, to determine the necessity of gut bacteria for male aggregation pheromone release. A combination of antibiotic-mediated bacterial depletion, quantitative PCR, gas chromatography-mass spectrometry (GC-MS), and Y-tube olfactometry was employed. Antibiotic treatment resulted in a marked reduction in gut bacterial load and a concomitant decrease of more than 85% in the emission of two key pheromone components, 2,6,10,14-tetramethylheptadecane and heptacosane. Behavioral assays demonstrated that females no longer exhibited significant attraction to treated males. Furthermore, defined recolonization with a single cultured gut isolate, Acinetobacter guillouiae, was sufficient to rescue pheromone emission. This indicates that particular gut taxa, rather than microbial biomass alone, are essential for pheromone biosynthesis. These findings demonstrate a decisive role of gut bacteria in the chemical communication of Trigonorhinus sp. and highlight the potential of symbiont-targeted strategies for pest management.

In recent years, a Trigonorhinus sp. (Coleoptera) has caused serious damage to Caragana liouana Zhao Y. Chang and Yakovlev, a major ecological restoration shrub in China. Here, we survey the occurrence and damage pattern of Trigonorhinus sp. and its galls and compare the growth of affected and unaffected plants. Trigonorhinus sp. larvae usually infest the main trunk and lateral branches of the plant, causing the affected branches to become partially swollen and verrucose. Galls develop in stages depending on whether eggs are laid in May or July and proceed in sequence over three years from egg-laying to formation, expansion, dormancy, maturity, dormancy, maturity, and death. Galls inhibit plant development to some extent. On average, six (at least one, and no more than 18; standard error of the mean = 3) larvae occupy each gall, and the number of larvae within a gall did not significantly affect gall size. Gall size significantly affected branch dieback, and large-diameter infested branches had larger galls. This study clarifies the growth dynamics of Trigonorhinus sp. galls and provides a basis for further research into the growth mechanism of the species’ galls.

Soil heavy metal contamination has emerged as a critical global environmental challenge, with China facing a particularly severe situation due to intensive industrial, mining, and agricultural acti...

Toll-like receptors (TLRs) are conserved pattern recognition receptors essential to insect innate immunity. However, the functions of TLRs in Loxostege sticticalis, a destructive agricultural pest, remain poorly characterized. In this study, the full-length coding sequence of the L. sticticalis Toll receptor (LsToll) was identified and characterized to analyze its molecular features. Structural analysis showed that LsToll possesses typical Toll family features, including an extracellular domain containing 19 leucine-rich repeats (LRRs), a transmembrane helix, and a highly conserved intracellular Toll/interleukin-1 receptor (TIR) domain. LsToll transcript levels were significantly upregulated after bacterial challenge. RNAi-mediated silencing of LsToll significantly reduced larval tolerance to bacterial infection and increased mortality. Notably, LsToll suppression also induced severe developmental abnormalities, including molting obstruction, pupation failure, and defects in wing expansion in newly emerged adults. Transcriptome analysis after RNAi identified 5230 differentially expressed genes (DEGs), which were significantly enriched in insect hormone biosynthesis and metabolic pathways. Biochemical assays further confirmed that LsToll knockdown decreased 20-hydroxyecdysone (20E) titers and increased juvenile hormone III (JH III) titers. These results suggest that LsToll contributes to antibacterial defense and normal development in L. sticticalis. Its involvement in both survival and development indicates that LsToll may serve as a promising molecular target for sustainable pest management strategies.