Adaptation of fine root plasticity to soil nutrients heterogeneity in natural forest ecosystems has not been well explored. The study aimed to determine seasonal variations of fine root traits in Pinus koraiensis natural forests and explore the relationship between fine root traits and soil properties. Root and soil samples were collected from the coniferous broad-leaved mixed forest (BP), monospecific P. koraiensis forest (MP), and coniferous mixed forest (CP). Soil available phosphorus (P) content for MP was 31.7% and 39.8% lower than for BP and CP. Soil cation exchange capacity (CEC) for MP was lower by 23.5% and 27.2% than for BP and CP, respectively. In July, specific root lengths and root surface areas for BP and CP (mixed forests) were significantly higher than for MP (monospecific forest). A structural equation model showed that CEC had a significant effect on fine root traits. Root diameter, root volume density, and root surface area density were negatively correlated with CEC. Fine root traits plasticity of P. koraiensis are closely related to soil available nutrient contents, CEC, and species composition at the ecosystem level.

The widespread use of insecticides in forest ecosystems has raised significant concerns about their nontarget effects on biological control agents (BCAs), such as predators and parasitoid wasps, which play a pivotal role in natural pest suppression. This review evaluates the lethal and sublethal impacts of various insecticide classes on BCAs. Systemic insecticides, while effective in controlling pests, have been shown to impair the reproduction, foraging behavior, and host-seeking abilities of BCAs, leading to disruptions in pest regulation and biodiversity loss. In Pinus koraiensis (Siebold & Zucc) forests, parasitoid wasps such as Baryscapus dioryctriae (Yang & Song) are critical for managing pests such as Dioryctria pryeri. However, insecticide exposure threatens their efficacy, exacerbating pest outbreaks and ecosystem instability. The deployment of B. dioryctriae as a BCA provides a sustainable alternative to chemical control, with demonstrated success in reducing pest populations and minimizing environmental impacts. Integrated pest management (IPM) frameworks that combine biological control with targeted insecticide use offer promising solutions to mitigate nontarget effects. Future research should focus on optimizing mass-rearing and release strategies for BCAs, exploring semiochemical-based pest disruption and assessing the long-term ecological consequences of low-dose insecticide exposure. By advancing IPM approaches, forest managers can achieve effective pest control while preserving the ecological integrity and biodiversity of forest ecosystems.

Insects’ growth and development are highly dependent on energy supply, with sugar metabolism playing a pivotal role in maintaining homeostasis and regulating physiological processes. The present study investigated the effects of exendin-4, a glucagon-like peptide-1 receptor (GLP-1R) agonist, on the growth, development, glycolysis, and energy metabolism of fourth-instar larvae of the fall webworm, Hyphantria cunea. We determined the impact of exendin-4 on larval growth and nutritional indices, analyzed the responses of glycolytic and metabolic pathways, and revealed the underlying regulatory mechanisms. Exendin-4 treatment significantly decreased growth and nutritional indices, influenced the activity of digestive enzymes, and induced changes in metabolite profiles, particularly affecting energy substance metabolism. We observed an increase in the glycogen content and a decrease in glucose and trehalose levels in the hemolymph, suggesting a regulatory effect on blood sugar homeostasis. Furthermore, exendin-4 promoted glycolysis by enhancing the activities and expressions of key glycolytic enzymes, leading to an increase in pyruvate production. This was accompanied by a reduction in ATP levels and the activation of AMP-activated protein kinase (AMPK), which may underlie the growth arrest in larvae. Our findings provide novel insights into the effects of exendin-4 on insect responses from an energy metabolism perspective and may contribute to the development of GLP-1R agonists for pest management.

Hazel (Corylus avellana) is easily attacked by Curculio nucum L. To better understand the physiological mechanisms underlying the different resistance of cultivars to C. nucum, we determined the insect-resistant compounds, plant hormones contents, and enzyme activities in the nutshells of three hazel cultivars (DW, B21, and MZ) before (preexisting defense) and after (induced defense) C. nucum chewing. The findings demonstrated that the resistance of three hazel cultivars to C. nucum differed significantly (p < 0.05): the damage rate of MZ with 17.57% was highest, followed by DW (11.23%), and then B21 (7.15%). The contents of insect-resistant compounds (total terpenoid, tannin, total phenol, flavonoids, cellulose, and lignin) varied with hazel cultivars, both before and after C. nucum chewing, except for cellulose and lignin before induction. The level of plant hormones and defense enzyme activities of hazelnut enhanced due to C. nucum induction. Pearson correlation results revealed that the hazelnut damage rate was significantly negatively correlated with jasmonic acid (JA) (R2 = 0.812), SOD (R2 = 0.671), salicylic acid (SA) (R2 = 0.878), and terpenoids (R2 = 0.774), and significantly positively correlated with flavonoids (R2 = 0.696), celluloses (R2 = 0.501), POD (R2 = 0.758), and abscisic acid (ABA) (R2 = 0.978). The hazelnut defense to C. nucum was negatively related to cellulose contents, and not to lignin contents, but was significantly positively related to the ratio of cellulose-to-lignin (R2 = 0.703). Our results suggested that the hazel against C. nucum attack responded by improving plant hormones contents and enzyme activities in the nutshells. A particular cellulose-to-lignin ratio provides the most effective physical structural defense properties in the nutshells.

The hazelnut weevil larvae (Curculio dieckmanni) is a major pest of nut weevils, spending part of its life cycle in the soil and causing significant damage to hazelnut crops. Moreover, its concealed feeding behavior complicates effective control with chemical insecticides. The entomopathogenic nematode Steinernema carpocapsae, which efficiently kills weevil larvae, offers a promising biological control agent. To investigate the molecular responses of hazelnut weevil larvae to nematode infection, we employed integrated transcriptomic and proteomic analyses following infection by S. carpocapsae. Our results revealed substantial alterations in gene expression, particularly the upregulation of immune-related transcripts such as antimicrobial peptides (AMPs) and stress-responsive proteins like heat shock protein 70 (HSP70). Furthermore, significant metabolic reprogramming occurred, marked by the downregulation of carbohydrate metabolic pathways and activation of energy conservation mechanisms. Although we observed an overall correlation between mRNA and protein expression levels, notable discrepancies highlighted the critical roles of post-transcriptional and post-translational regulatory processes. Collectively, these findings advance our understanding of the molecular interaction between insect hosts and pathogenic nematodes and contribute valuable knowledge for enhancing the effectiveness of EPN-based pest management strategies.