A Review of the Host Plant Location and Recognition Mechanisms of Asian Longhorn Beetle

Identification of Attractants from Three Host Plants and How to Improve Attractiveness of Plant Volatiles for Monochamus saltuarius

As a new vector insect of pine wood nematodes in China, the Monochamus saltuarius (Coleoptera: Cerambycidae) vectors pine wilt nematodes into healthy pine trees through feeding and oviposition, resulting in huge economic losses to forestry. A promising control strategy is to develop safe and efficient attractants. This study aims to screen for the key active volatiles of Pinus koraiensis (Pinales: Pinaceae), Pinus tabuliformis (Pinales: Pinaceae), and Picea asperata (Pinales: Pinaceae) that can attract M. saltuarius, and to study the synergistic attraction of the main attractant plant volatiles with ethanol and insect aggregation pheromones. The preference of M. saltuarius for three hosts is P. koraiensis > P. tabuliformis > Picea asperata. We detected 18 organic volatiles from three host plants. Through EAG assays and indoor Y-tube behavioral experiments, 3-carene, (-)-camphor, β-pinene, α-phellandrene, terpinolene, α-pinene, D-limonene, and myrcene were screened to have attractive effects on M. saltuarius. We found that 3-carene, β-pinene, and α-pinene are the most attractive kairomones in field experiments, which may play a crucial role in the host localization of M. saltuarius. Ethanol has a synergistic effect on the attractant activity of 3-carene and β-pinene, and the synergistic effect on β-pinene is the best. The mixture of ethanol, 2-undecyloxy-1-ethanol, and ipsdienol can significantly enhance the attraction effect of β-pinene on M. saltuarius. These new findings provide a theoretical basis for the development of attractants for adult M. saltuarius and contribute to the green control of M. saltuarius.

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.

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.

Research on Photoinduction-Based Technology for Trapping Asian Longhorned Beetle (Anoplophora glabripennis (Motschulsky, 1853) (Coleoptera: Cerambycidae)

Light traps play a crucial role in monitoring pest populations. However, the phototactic behavior of adult Asian longhorned beetle (ALB) remains enigmatic. To provide a theoretical foundation to select the suitable light emitting diode (LED)-based light sources used for monitoring ALB, we compared the effect of exposure time on the phototactic response rates of adults at wavelengths of 365 nm, 420 nm, 435 nm, and 515 nm, and found that the phototactic rate increased gradually when the exposure time was prolonged, but there was no significant difference between different exposure times. We evaluated the effect of diel rhythm and found the highest phototactic rate at night (0:00-2:00) under 420 nm and 435 nm illumination (74-82%). Finally, we determined the phototactic behavioral response of adults to 14 different wavelengths and found both females and males showed a preference for violet wavelengths (420 nm and 435 nm). Furthermore, the effect of the light intensity experiments showed that there were no significant differences in the trapping rate between different light intensities at 120 min exposure time. Our findings demonstrate that ALB is a positively phototactic insect, showing that 420 nm and 435 nm are the most suitable wavelengths for attracting adults.