Description of external morphological characteristics and molecular identification of a bark beetle in hazel garden of northeastern China

Objective A species of bark beetle causing severe damage has been discovered in hazelnut orchards in northeastern China. This pest bores into the trunks and branches of hazelnut trees, resulting in widespread tree mortality. To identify the bark beetle species and better guide its control measures, morphological observations and molecular biological identification of the bark beetle were conducted.

Method The external morphological characteristics of bark beetle at various developmental stages (eggs, larvae, pupae, and adults) were observed and described using optical microscopy and scanning electron microscopy. Concurrently, whole-genome DNA was extracted from the bark beetles. Specific gene fragments of 28S ribosomal DNA (28S rDNA) and cytochrome c oxidase subunit I (COI) were amplified through PCR technology. The obtained sequences were compared with existing bark beetle gene sequences in the GenBank database, followed by the construction of phylogenetic trees to perform molecular phylogenetic analysis.

Result Significant dimorphism was observed between male and female bark beetles, with males (adult body length: (2.00 ± 0.10) mm) being notably smaller than females (adult body length: (3.00 ± 0.15) mm). The hindwings of male adults were reduced, with the eighth tergite of the abdomen distinctly exposed and the last abdominal segment being greatly enlarged. Morphological descriptions and comparative analyses taxonomically classified this bark beetle within the tribe Xyleborini. Molecular identification revealed high congruence between the bark beetle’s 28S rDNA and COI gene fragments and those of Anisandrus dispar in the GenBank database. The species was conclusively identified as Anisandrus dispar.

Conclusion Through morphological and molecular analyses, the severely damaging bark beetles in hazelnut orchards of northeastern China is identified as Anisandrus dispar. Morphological traits across all developmental stages are documented in detail, providing comprehensive morphological datasets and partial DNA sequence data. These outcomes establish a theoretical foundation for further research on Anisandrus dispar and the development of targeted pest management strategies.