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Background: Global climate change is causing an increase in extreme high temperatures (EHTs), which subject insects to unprecedented stress. Behavior plasticity in response to EHTs, particularly oviposition behavior, is important for the persistence and outbreak of insect populations. Investigating the plasticity of oviposition behavior and its underlying mechanisms has theoretical importance to pest management, but knowledge gaps still remain. Results: Herein, we characterized the reproductive traits of Monochamus alternatus, a dominant insect vector of the destructive pine wilt disease, including oviposition behavioral patterns, fecundity, offspring fitness and sperm viability, under simulated heatwave conditions in the laboratory. The results showed that (i) EHTs induced a novel oviposition behavior, whereby females deposited multiple eggs into a single groove rather than laying one egg per groove under normal condition; (ii) EHTs exerted stage‐ and sex‐specific effects on fecundity, offspring fitness and sperm viability; and (iii) there was a significant correlation between frequency of the novel oviposition strategy and sperm viability. Conclusion: We hypothesized that this beetle pest has the ability to flexibly shift towards a low‐cost oviposition strategy to counteract the fitness costs caused by heat stress. Taken together, these findings provide a theoretical foundation for personalized pest management strategies in the context of climate change. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Conifers have evolved sophisticated terpenoid defenses for protection against herbivores and pathogens. Pinus massoniana Lamb. is the most widely distributed pioneer afforestation and resin tree species in China, but is seriously harmed by pine wilt disease. Monochamus alternatus is the main vector of pine wilt disease in China. Monoterpenes, sesquiterpenes and diterpenes, the main secondary defensive compounds of P. massoniana, are catalyzed by different terpene synthases (TPSs), which participate in the important defense pathways against external biotic and abiotic stresses. Here, we aimed to identify the terpene synthases (TPSs) in P. massoniana, responding to the feeding of M. alternatus, and to characterize the functions and products of the mono-TPSs. We identified six differentially expressed TPS genes in the P. massoniana fed upon by M. alternatus, including four mono-TPS and two sesqui-TPS genes. The functions of the four mono-TPSs were verified by analysis of the main product and by-products of these mono-TPSs. (+)-α-Pinene, (−)-α-pinene, and limonene were the major products of TPS (+)-α-pinene, TPS (−)-α-pinene, and TPS limonene, respectively, but TPS (−)-β-pinene only catalyzed a trace amount of (−)-β-pinene in the products. Our findings shed light on the potential relationships between the structure of terpene synthases and their corresponding products. [ABSTRACT FROM AUTHOR]

Plants play an important role in interactions between insect herbivores and their pathogens. The ability of host plants to modify the infectivity of entomopathogens in herbivorous insects has been widely documented. However, the plants' nutrients have always been neglected as a factor contributing to variation in the susceptibility of insect herbivores to entomopathogens. The fall-webworm (FWW), Hyphantria cunea Drury, is a typical polyphagous caterpillar, and the Hyphantria cunea nucleopolyhedrovirus (HycuNPV) is a distinctly specialized baculovirus for the FWW, which is safe for other organisms and has been effectively used as a biological insecticide against H. cunea in China. In this study, we investigated the nutrient components of four host plant species, i.e., Prunus serrulate, Cerasus serrulate, Camptotheca acuminata, and Populus deltoides, and their effects on the susceptibility of H. cunea larvae to HycuNPV. The HycuNPV-infected larvae fed on P. deltoides leaves exhibited higher survival rates, longer survival times, more food intake, and gained larger body size. These biological parameters were positively correlated with the nitrogen components of host plant leaves. Moreover, the larval antioxidant enzymes exhibited different responses to HycuNPV. HycuNPV infection significantly triggered the catalase (CAT) and prophenoloxidase (PPO) enzyme activity levels of H. cunea larvae. The uninfected larvae fed on poplar leaves induced a robust increase in the POD activity, which could scavenge extra reactive oxygen species and provide a protective effect against the HycuNPV. In conclusion, the plant-mediated effects of HycuNPV on the FWW have been investigated in this study. The nitrogen content in dietary was an essential factor in determining the insect herbivore susceptibility to entomopathogenic viruses, and it helped explain variations in the susceptibility of pests to the entomopathogenic viruses and aid in developing more robust tolerance monitoring assays in the lab that reflect the performance of pests in the field. [ABSTRACT FROM AUTHOR]

Hyphantria cunea Drury (Lepidoptera: Erebidae) is a quarantine pest in China that can cause damage to hundreds of plants. As biological control agents, Nuclear Polyhedrosis Virus (NPV) and Bacillus thuringiensis Berliner (Bacillales: Bacillaceae) (Bt) are commonly used to inhibit the prevalence of H. cunea. To investigate the role of midgut bacteria in the infection of NPV and Bt in H. cunea , we performed a series of tests, including isolating the dominant culturable bacteria in the midgut, eliminating intestinal bacteria, and respectively inoculating the dominant strains with NPV and Bt for bioassay. Two dominant bacteria, Klebsiella oxytoca Lautrop (Enterobacterales: Enterobacteriaceae) and Enterococcus mundtii Collins (Lactobacillales: Enterococcaceae), in the midgut of H. cunea were identified, and a strain of H. cunea larvae without intestinal bacteria was successfully established. In the bioassays of entomopathogen infection, K. oxytoca showed significant synergistic effects with both NPV and Bt on the death of H. cunea. In contrast, E. mundtii played antagonistic effects. This phenomenon may be attributed to the differences in the physico-chemical properties of the two gut bacteria and the alkaline environment required for NPV and Bt to infect the host. It is worth noting that the enhanced insecticidal activity of K. oxytoca on NPV and Bt provides a reference for future biological control of H. cunea by intestinal bacteria. [ABSTRACT FROM AUTHOR]

Camphor, Cinnamomum camphora (L.) Presl, is used for mothproofing material due to its content of secondary metabolites. However, the phloem‐feeding weevil, Pagiophloeus tsushimanus (Coleoptera: Curculionidae), has been observed to feed exclusively on this plant without incurring apparent fitness costs. This phenomenon remains to be elucidated.Gas chromatography–mass spectrometry analysis of essential oil extracted from the phloem of camphor tree was performed. The top three components, all monoterpenoids, were eucalyptol (31.9%), D‐camphor (19.2%) and linalool (10.2%), respectively.In headspace bioassays, both eggs and larvae showed the greatest sensitivity to eucalyptol, and there was a bell‐shaped relationship between the concentrations used and developmental time for eggs when exposed to D‐camphor volatile.Exposure to essential oil mixture and D‐camphor notably increased the activity of glutathione S‐transferase in the weevil. A corresponding short‐term induction of gene expression was also observed according to quantitative real‐time polymerase chain reaction analysis.In general, P. tsushimanus possessed various levels of tolerance to different host monoterpenoids. Over‐expression of glutathione S‐transferase in vivo probably relates to detoxification metabolism of these monoterpenoids. Our findings provide a valuable clue to understanding the mechanism underlying resistance to host‐specific chemical defences in this weevil pest. [ABSTRACT FROM AUTHOR]

A substantial increase in the occurrence of extremely high‐ or low‐temperature events caused by global climate change has imposed pressure on the survival and reproduction of invertebrates. Hyphantria cunea (H. cunea; Lepidoptera: Arctiidae) is a worldwide defoliator and has become a major forestry and agricultural pest during the past three decades in China. The thermal and cold tolerance has directly affected the population and geographical distribution of H. cunea, which remains poorly understood. Here, we examined the thermal tolerance of H. cunea larvae and discovered that they could endure extremely high temperatures, as demonstrated by median lethal times (Ltim50) of 103.3 hr at 37°C, 62.0 hr at 40°C and even 14.5 hr at 43°C. To further explore the molecular evidence of the physiological response to heat and cold, we cloned and characterized six small heat shock proteins (sHSPs). These proteins possessed the conserved α‐domain of the sHSP family at the C‐terminus and various N‐terminal domains. Phylogenetic analysis showed that the HCsHSPs presented a close evolutionary relationship with sHSP genes in noctuidae species. Four sHSPs in H. cunea were sensitive to heat stress, and only HCsHSP28.7 was induced by cold stress. The expression level of HCsHSPs peaked at 40°C and decreased in treatment at 45°C. HCsHSP20.0 transcripts were abundant in the cuticle after heat shock, and HCsHSP28.7 was most enriched in the fat body after cold shock. In addition, an equal molecular weight of the HCsHSP20.0 protein could completely protect malate dehydrogenase (MDH) from thermal aggregation. Recombinant HCsHSP28.7 E. coli cells exhibited tolerance to cold stress. Overall, our results demonstrate that HCsHSPs, especially HCsHSP20.0 and HCsHSP28.7, are vital genes in the adaptation of H. cunea larvae to extreme conditions in the context of global climate change. [ABSTRACT FROM AUTHOR]

Native to Asia, Euwallacea interjectus (Blandford) (Coleoptera: Curculionidae: Scolytinae) is a destructive and invasive pest of live trees, and now it has been found in the United States and Argentina. In recent years, this pest appeared in high densities in poplar monocultures from Eastern China (Jiangsu and Shanghai) and Argentina and caused significant poplar mortality. However, the origin of the pests related to tree damage and the Fusarium mutualists from some poplar zones in China remained unclear. Here, we provided a broader phylogeographic analysis of E. interjectus based on the mitochondrial gene (cytochrome c oxidase I) to determine the global genetic structure of this species. Five mitochondrial lineages were found in the native area. Populations introduced to the United States were originated from 4 localities. The Argentine population was derived from Japan. The species was observed with strikingly high level of cytochrome c oxidase I intraspecific divergence that exceeded interspecific divergence, but the high intraspecific variation was correlated with geographical locations among the native populations. Two nuclear genes (arginine kinase and carbamoyl-phosphate synthetase 2-aspartate transcarbamylase-dihydroorotase) were more conservative, and intraspecific differences were lower than interspecific differences. The mitochondrial genetic variation was probably caused by evolution of lineages among geographically isolated populations. But it is immature to infer the existence of cryptic species based on cytochrome c oxidase I differences. All samples collected from poplar populations were indigenous and formed close relationship with a specimen from eastern and southern China. Surprisingly, pests from poplar populations in Jiangsu and Shanghai showed different haplotypes and mutualists. This suggested that the control strategies should consider the genetic and mutualistic diversity of beetles at different poplar localities., (© The Author(s) 2024. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)