Longwave ultraviolet (UVA) light, in the range of 315–400 nm, has been widely used as a light source in the light trapping of insect pests. Previous studies have demonstrated the oxidative stress and lethal effect of UV radiation on insects. In this study, we evaluated the influence of UVA radiation on the antioxidant and detoxifying enzymes of Dendrolimus tabulaeformis. We tested the contents of malondialdehyde (MDA), hydroxyl radical (·OH), hydrogen peroxide (H₂O₂), reduced glutathione (GSH), and oxidized glutathione (GSSH) following different exposure time periods of UVA light irradiation on D. tabulaeformis adults. In addition, we investigated how the activities of antioxidant and detoxifying enzymes responded to UVA radiation by determining the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), polyphenol oxidase (PPO), glutathione S-transferase (GST), glutathione reductase (GR), acetylcholinesterase (AChE), carboxylesterase (CarE), alkaline phosphatase (ALP), and acid phosphatase (ACP). Adults were exposed to UVA light for different time periods (0, 5, 15, 30, 60, and 120 min). We found that exposure to UVA light for 5 min resulted in rapid variation in the activities of the antioxidant and detoxification enzyme systems. However, the antioxidant capacity of females was incongruous with that of males following UVA irradiation. Our results confirmed that UVA light irradiation increased the level of oxidative stress and disturbed physiological detoxification in D. tabulaeformis adults. Based on the above results, we anticipated that further research of the mechanism of UVA irradiation on the antioxidant and detoxifying enzymes of D. tabulaeformis would gain more importance, allowing to develop and use new, less toxic and environmentally friendly pesticides.

Sirex noctilio along with its mutualistic fungal symbiont, Amylostereum areolatum (a white rot fungus), is an invasive pest that causes excessive damage to Pinus plantations in Northeast China. In 2015, S. noctilio were found to attack Pinus sylvestris var. mongolica, and often share larval habitat with the native woodwasp, S. nitobei. The objective of this study was to determine the possible origin(s) of the introduced pest complex in China and analyse the genetic diversity between A. areolatum isolated from invasive S. noctilio, native S. nitobei and other woodwasps collected from Europe (native range) and other countries. Phylogenetic analyses were performed using the intergenic spacer (IGS) dataset and the combined 4-locus dataset (the internal transcribed spacer region (ITS), translation elongation factor alpha 1 (tef1), DNA-directed ribosomal polymerase II (RPB2), and mitochondrial small subunit (mtSSU)) of three Amylostereum taxa. The multilocus genotyping of nuclear ribosomal regions and protein coding genes revealed at least three distinct multilocus genotypes (MLGs) of the fungus associated with invasive S. noctilio populations in Northeast China, which may have come from North America or Europe. The IGS region of A. areolatum carried by S. noctilio from China was designated type B1D2. Our results showed a lack of fidelity (the paradigm of obligate fidelity to a single fungus per wasp species) between woodwasp hosts and A. areolatum. We found that the native S. nitobei predominantly carried A. areolatum IGS-D2, but a low percentage of females instead carried A. areolatum IGS-B1D2 (MLG A13), which was presumably due to horizontal transmission from S. noctilio, during the sequential use of the same wood for larval development. The precise identification of the A. areolatum genotypes provides valuable insight into co-evolution between Siricidae and their symbionts, as well as understanding of the geographical origin and history of both Sirex species and their associated fungi.

Sirex noctilio F. (Hymenoptera: Siricidae) is an invasive woodwasp from Europe and North Africa. Globalization has led to an expanding global presence in pine forests. S. noctilio has been previously introduced outside of its native range and now co-occurs in trees with native S. nitobei Matsumura (first discovered in 2016). Damage to Pinus sylvestris var. mongolica Litv in northeast China can be attributed to two types of woodwasp. To distinguish the two species by the traditional taxonomic morphology, we mainly differentiate the color of the male’s abdomen and the female’s leg. There remains intraspecific variation like leg color in the delimitation of related genera or sibling species of Sirex woodwasps. In this study, we used landmark-based geometric morphometrics including principal component analysis, canonical variate analysis, thin-plate splines, and cluster analysis to analyze and compare the wings, ovipositors, and cornus of two woodwasps to ascertain whether this approach is reliable for taxonomic studies of this group. The results showed significant differences in forewing venation and the shapes of pits in the middle of ovipositors among the two species, whereas little difference in hindwings and cornus was observed. This study assists in clarifying the taxonomic uncertainties of Siricidae and lays a foundation for further studies of the interspecific relationships of the genus Sirex.

The mutualistic symbiosis relationship between the gut microbiome and their insect hosts has attracted much scientific attention. The native woodwasp, Sirex nitobei, and the invasive European woodwasp, Sirex noctilio, are two pests that infest pines in northeastern China. Following its encounter with the native species, however, there is a lack of research on whether the gut microbiome of S. noctilio changed, what causes contributed to these alterations, and whether these changes were more conducive to invasive colonization. We used high-throughput and metatranscriptomic sequencing to investigate S. noctilio larval gut and frass from four sites where only S. noctilio and both two Sirex species and investigated the effects of environmental factors, biological interactions, and ecological processes on S. noctilio gut microbial community assembly. Amplicon sequencing of two Sirex species revealed differential patterns of bacterial and fungal composition and functional prediction. S. noctilio larval gut bacterial and fungal diversity was essentially higher in coexistence sites than in separate existence sites, and most of the larval gut bacterial and fungal community functional predictions were significantly different as well. Moreover, temperature and precipitation positively correlate with most of the highly abundant bacterial and fungal genera. Source-tracking analysis showed that S. noctilio larvae at coexistence sites remain dependent on adult gut transmission (vertical transmission) or recruitment to frass (horizontal transmission). Meanwhile, stochastic processes of drift and dispersal limitation also have important impacts on the assembly of S. noctilio larval gut microbiome, especially at coexistence sites. In summary, our results reveal the potential role of changes in S. noctilio larval gut microbiome in the successful colonization and better adaptation of the environment.

Sirex noctilio and Amylostereum areolatum form a highly specific mutualistic symbiosis. The growth and host-degrading activities of the symbiotic fungus are critical to the woodwasps, which directly influence the larval survival rate and adult body size of the woodwasps. Gene expression analysis has been extensively employed to decrypt the intricate growth patterns of symbiotic fungi and identify the associated functional genes underpinning their degradation pathways. Appropriate reference genes are crucial for enhancing the accuracy of studies on gene expression. In an effort to refine gene expression analysis in A. areolatum, our study cultivated the symbiotic fungi on the wood powder medium of Pinus sylvestris var. mongolica, aligning closer to its natural growth conditions. Thirteen reference genes underwent meticulous evaluation via algorithms such as delta Ct, geNorm, BestKeeper, RefFinder, and NormFinder, depending on their stability amidst diverse growth and developmental epochs of A. areolatum. α-TUB, P450, and the combination (α-TUB + P450) were distinguished as the most stable candidates for RT-qPCR analysis, confirmed through AaLac1 expression validation. These findings contribute significantly to the investigation of gene expression in A. areolatum and facilitate a deeper understanding of its symbiotic relationship with S. noctilio.

The stem blight disease on Elaeocarpus spp. was newly identified in 2022 on E. rugosus and E. hain in Guangzhou, representing a serious stem disease that causes branch rot and cankers in Elaeocarpus species and can lead to whole-plant death in severe cases. Strain ZX-13 was isolated from Elaeocarpus rugosus stems and showed excellent antagonism against the Elaeocarpus stem blight pathogen Pseudocryphonectria elaeocarpicola. Based on morphological characteristics, physiological and biochemical results, and molecular biology analyses, the strain was identified as Erwinia phyllosphaerae. Whole-genome sequencing and annotation indicate that strain ZX-13 has a high-quality draft assembly of 4,686,433 bp, with a GC content of 53.85%, encoding 4189 genes, 86 tRNA, 22 rRNA, and 110 ncRNA. Eight antifungal enzymes from the GH family may be crucial factors to its antagonistic activity. Using antiSMASH 7.1.0, the ZX-13 genome predicted eight BGCs (RiPPs, NRPs, terpenes, etc.), with one showing 100% similarity to carotenoid biosynthesis. Novel candidates include an O-antigen, hassallidin C, and lankacidin C. The study identified Erwinia phyllosphaerae ZX-13 as an antagonistic bacterial strain for the first time, indicating substantial potential for biocontrol applications.