Tuta absoluta is a major pest, damaging tomato crops in many countries. Spinetoram, a novel insecticide, is increasingly used for the management of various insect pests. However, limited information is available on its lethal effects on T. absoluta. Therefore, this study was carried out to evaluate the toxicity of spinetoram concentrations in T. absoluta by exposing third-instar larvae to this insecticide through leaf-dipping bioassays under laboratory conditions. The results showed that sublethal spinetoram concentrations (LC₁₀ and LC₂₀) extended the developmental duration of the larval and pupal stage, as well as the oviposition period, and decreased the pupal weight, pupation and eclosion rates, fecundity, sex ratio, and egg-hatching rate compared to the control group. LC₁₀ and LC₂₀ treatments up-regulated the activity of superoxide dismutase and catalase antioxidant enzymes in T. absoluta larvae by 51.14–88.72% and 39.34–87.76% at 12 h, 62.71–96.68% and 37.38–39.92% at 24 h, and 41.78–53.34% and 19.44–48.39% at 48 h, respectively, compared to the control. Conversely, the LC₁₀ and LC₂₀ treatments inhibited the activities of detoxifying enzymes, i.e., carboxylesterase (14.72–34.95%), acetylcholinesterase (9.02–48.86%), glutathione S-transferase (19.40–43.19%), and mixed-function oxidase (18.18–25.93%). These findings indicate that lethal concentrations of spinetoram influence the population dynamics of T. absoluta by reducing their survival and developmental potential and inhibiting the activity of detoxifying enzymes.

Glycerophosphocholine (GPC) is a water-soluble small molecule found naturally in humans and foods such as milk and soybeans. It can activate the IIS pathway by regulating the expression of daf-2, ins-18 and daf-16 genes, sek-1 and skn-1 genes of MAPK pathway, sod-3, ctl-1, gst-4 and other antioxidant genes. GPC can relieve symptoms related to aging in organisms. The aim of this study was to probe the effects of GPC on the longevity and stress resistance of the entomopathogenic nematode (EPN) Steinernema kraussei 0657L strain. The results showed that the lifespan of S. kraussei 0657L was significantly prolonged by 50 mM GPC treatment, which was 54.55% longer than that of the control (0 mM GPC). GPC significantly inhibited reactive oxygen species (ROS) and lipofuscin accumulation, but the body size and fecundity of S. kraussei 0657L had little changed. At the same time, the longevity of S. kraussei 0657L exposed to heat shock and UV-B radiation was significantly prolonged than that with no external stress. GPC supplementation increased the activity of antioxidant enzymes and corresponding gene expression. Under treatment with 50 mM GPC, the activities of superoxide dismutase and catalase were increased by 1.90- and 4.13-fold, respectively, the expression of the sod-3 and ctl-1 genes was increased by 3.60- and 0.60-fold, respectively, and harmful reactive oxygen species were removed. In addition, the expression levels of the ins-18, skn-1, sek-1 and gst-4 genes related to the insulin/IGF-1 signaling pathway were upregulated 1.04-, 1.84-, 2.21- and 1.24-fold, respectively. These results indicate that GPC is mainly involved in the lifespan regulation of S. kraussei 0657L and plays an important role in resistance to external stress by activating the insulin/IGF-1 signaling pathway and downstream PI3K/MAPK kinase, creating a new idea for improving the commercial efficacy of S. kraussei. It also laid a theoretical foundation for its further efficient development and utilization in the field of biological control.

The free-living infective juveniles of entomopathogenic nematodes (EPNs) are critical biological control agents against insect pests. The field efficacy of EPNs is largely determined by their tolerance to low-humidity stress, a trait closely linked to the mobilization of their energy reserves. This study aims to investigate how varying levels of humidity stress influence energy reserve dynamics in two EPNs, Steinernema kraussei 0657L and Heterorhabditis brevicaudis 0641TY, and their relationship with the survival rate and pathogenicity. The results demonstrated that lipids were the predominant energy reserve, followed by proteins and sugars. Notably, neutral lipid constituted approximately 3% of the total lipid content. Among sugars, soluble sugar levels were the highest, followed by glycogen and trehalose. Exposure to low-humidity stress resulted in increased levels of protein, total lipid, glycogen, and trehalose in nematodes. These increases were more pronounced in S. kraussei 0657L, a highly drought-resistant strain, compared to H. brevicaudis 0641TY. Furthermore, the accumulation of protein, total lipid, and trehalose was negatively correlated with survival rate and pathogenicity. However, positive correlations were observed between trehalose and both total lipids and soluble sugars. Furthermore, transcriptome analysis revealed that under low-humidity stress, S. kraussei 0657L exhibited an enrichment of differentially expressed genes (DEGs) involved in glycolysis/gluconeogenesis, fatty acid metabolism, and glycerophospholipid metabolism pathways. This indicates that S. kraussei 0657L regulated energy metabolism to adapt to low-humidity stress. These findings provide insights into the mechanisms underlying drought resistance in EPNs and offer an experimental basis for their application in arid environments.

Entomopathogenic nematodes (EPNs) are among the most promising biocontrol agents; however, their short shelf life constrains commercial application. This study evaluated the effects of storage temperature (6 °C and 25 °C) and sponge substrate moisture content (42%, 48%, and 55%) on the 18-week survival and post-storage virulence of two indigenous EPN species from Gansu Province, China: Heterorhabditis megidis 0627M and Steinernema feltiae 0619HT. A Generalized Linear Mixed Model (GLMM) revealed that storage duration, temperature, moisture content, and species all significantly affected survival of H. megidis 0627M and S. feltiae 0619HT (all p < 0.001). Low-temperature storage (6 °C) reduced mortality odds by 82.4% compared with room temperature (OR = 0.176, 95% CI: 0.117–0.263, p < 0.001). High moisture content (55%) increased mortality odds by 10.1-fold relative to moderate moisture (48%; OR = 10.114, 95% CI: 6.155–16.618, p < 0.001), whereas low moisture (42%) showed no significant difference from 48% (OR = 0.942, p = 0.810). The two species exhibited distinct adaptation strategies: S. feltiae 0619HT achieved the highest survival under low-temperature storage at 48% moisture content (56.48% at week 18), whereas H. megidis 0627M demonstrated a delayed competitive advantage under room-temperature, low-moisture conditions. Virulence assays revealed that low-temperature storage better preserved infectivity under most conditions. Notably, survival and virulence were not always concordant, necessitating their evaluation as complementary metrics. Species-specific storage protocols are proposed, providing a scientific basis for the future development of regionally targeted and cost-effective native EPN formulations, as well as for regionally targeted biocontrol applications.

The cotton bollworm, Helicoverpa armigera, is a major polyphagous agricultural pest that is notoriously difficult to control due to its broad host range, scattered oviposition, larval boring behavior, and strong resistance to both chemical insecticides and Bt proteins. Melatonin, an endogenous hormone ubiquitously present in living organisms, plays critical regulatory roles in various physiological processes, including metabolism, immunity, stress responses, and reproduction. Moreover, numerous studies have demonstrated that exogenous melatonin plays an important role in helping plants defend against diverse environmental stresses. In the present study, an artificial diet supplementation method was employed to investigate the effects of different concentrations of exogenous melatonin on the growth, development, and reproduction of H. armigera, with the aim of evaluating its potential application in integrated pest management (IPM). Larvae were treated with melatonin at concentrations of 0, 0.02, 0.2, 2, and 20 μg/g. The results showed that with increasing melatonin concentration, larval developmental duration was significantly prolonged, whereas pupal duration was significantly shortened (p < 0.05). At 20 μg/g, the longest larval duration (16.90 d) was recorded, representing an extension of 2.69 d compared with the control, while pupal duration (8.04 d) was reduced by 2.16 d relative to the control. Furthermore, higher melatonin concentrations significantly decreased larval head capsule width, larval body and pupal weight, and also significantly shortened adult longevity and oviposition period, while markedly reducing both total fecundity and daily fecundity per female. At 20 μg/g, the mean total fecundity per female reached its minimum (224.13 eggs), representing a reduction of 62.81% compared with the control. Collectively, these findings demonstrate that exogenous melatonin can significantly inhibit the growth, development, and reproduction of H. armigera, highlighting its potential application as a biorational tool in crop protection and integrated pest management.