Current and future control of the wood-boring pest Anoplophora glabripennis

PdPLR1 effectively enhances resistance of Populus deltoides 'shalinyang' to Anoplophora glabripennis by positive regulation of lignan synthesis

Anoplophora glabripennis (ALB) is one of the most devastating wood boring insects of poplars. Populus deltoides 'Shalinyang (PdS), a new poplar variety, shows strong resistance to ALB infestation. However, the molecular mechanism of insect resistance in PdS is unclear. Here, we found that lignan content was much higher in PdS phloem after ALB infestation than in healthy trees, and that adding lignan to artificial diet significantly reduced: larval weight; digestive enzyme activity (cellulase [CL], polygalacturonase [PG]); detoxification enzyme activity (carboxylesterase [CarE], glutathione S-transferase [GSH-ST]); and defense enzyme activity (Catalase [CAT]). We further identified the lignan biosynthesis-related PdPLR1 gene (Pinoresinol-lariciresinol reductase, PLR) based on transcriptome analysis, and it was significantly up-regulated in the PdS phloem attacked by ALB. Overexpression of PdPLR1 in Arabidopsis increased th lignan content. In contrast, silencing PdPLR1 in PdS significantly decreased expression levels of PdPLR1 and lignan content by 82.45% and 56.85%. However, silencing PdPLR1 increased the number of adults ovipositions and eggs hatching. The activity of CL, PG, CarE, GSH-ST and CAT and the biomass of larvae fed on phloem of PdS with silenced PdPLR1 were significantly higher than in the control. Taken together, up regulation of PdPLR1 enhanced PdS resistance to ALB by regulating lignan synthesis. Our findings provide in-depth insights into the molecular mechanisms of PdS-ALB interactions, which lay the foundation for understanding of defense in poplars to pest infection.

High Trunk Truncation as a Potential Sustainable Management Option for Asian Longhorned Beetle on Salix babylonica

The Asian longhorned beetle (ALB) causes substantial economic and ecological losses, thus, an environmentally friendly management strategy is needed. Here, we propose high trunk truncation (HTT), the removal of the above 200 cm portion of trees, as a sustainable management strategy to control ALB. To examine the hypothesis, an initial step involved the assessment of various biological characteristics of ALB. Subsequently, a controlled field experiment was carried out utilizing HTT. Finally, HTT was applied in two additional ALB infestation regions. The results of the study of the biological characteristics of ALB showed that 76.31-78.88% of frass holes and 85.08-87.93% of emergence holes were located on branches above 200 cm. Adults preferred to feed on branches 2-3 cm in diameter, ALB eggs were predominantly laid on 5 cm branches, and both were primarily located above 200 cm. These results revealed a correlation between the number of ALBs and the tree crown height. The controlled field experiment showed that the number of ALBs was significantly decreased when the HTT strategy was implemented: approximately 90% of frass holes and 95% of adults were eradicated by HTT compared with the control. Different field surveys involving HTT have shown similar results. These findings provide valuable insights into a sustainable and efficient management strategy for reducing the number of ALBs.

Effects of Fusarium solani on the Growth and Development of Anoplophora glabripennis Larvae

Anoplophora glabripennis (Asian longhorned beetle) is a wood-boring pest that can inhabit a wide range of healthy deciduous host trees in native and non-native habitats. Lignocellulose degradation plays a major role in the acquisition of nutrients during the growth and development of A. glabripennis larvae. In this study, the lignocellulose degradation capacity of Fusarium solani, a fungal symbiont of A. glabripennis, was investigated in fermentation culture and in four host tree species. The impact of F. solani on larval growth and survival parameters was assessed. Fermentation culture demonstrated continuous and stable production of lignocellulolytic enzymes over the cultivation period. Furthermore, F. solani was able to degrade host tree lignocellulose, as shown by decreased soluble sugar and cellulose contents and an increase in protein content. No significant differences in larval survival were observed in larvae fed with or without F. solani. However, weight and head capsule width were higher in larvae fed on F. solani, and gut lignocellulose activities were elevated in fed larvae. Our results indicate a role for F. solani in the predigestion of lignocellulose during the colonization and parasitic stages of A. glabripennis larval development, and also the F. solani an important symbiotic partner to A. glabripennis, lowering barriers to colonization and development in a range of habitats.

Integrated behavior and transcriptomic analysis provide valuable insights into the response mechanisms of Dastarcus helophoroides Fairmaire to light exposure

Light traps have been widely used to monitor and manage pest populations, but natural enemies are also influenced. The Dastarcus helophoroides Fairmaire is an important species of natural enemy for longhorn beetles. However, the molecular mechanism of D. helophoroides in response to light exposure is still scarce. Here, integrated behavioral, comparative transcriptome and weighted gene co-expression network analyses were applied to investigate gene expression profiles in the head of D. helophoroides at different light exposure time. The results showed that the phototactic response rates of adults were 1.67%-22.5% and females and males displayed a negative phototaxis under different light exposure [6.31 × 1018 (photos/m2/s)]; the trapping rates of female and male were influenced significantly by light exposure time, diel rhythm, and light wavelength in the behavioral data. Furthermore, transcriptome data showed that a total of 1,052 significantly differentially expressed genes (DEGs) were identified under different light exposure times relative to dark adaptation. Bioinformatics analyses revealed that the "ECM-receptor interaction," "focal adhesion," "PI3K-Akt signaling," and "lysosome" pathways were significantly downregulated with increasing light exposure time. Furthermore, nine DEGs were identified as hub genes using WGCNA analysis. The results revealed molecular mechanism in negative phototactic behavior response of D. helophoroides under the light exposure with relative high intensity, and provided valuable insights into the underlying molecular response mechanism of nocturnal beetles to light stress.