Aphis craccivora (Hemiptera: Aphididae) is an important pest affecting various crops worldwide. However, only few studies have been conducted on the infection of A. craccivora by Lecanicillium and related insecticidal mechanisms. We investigated the infection process of A. craccivora by Lecanicillium araneicola HK-1 using fluorescence microscopy and scanning electron microscopy (SEM), and our results indicated that the conidia of strain HK-1 easily attached to the feet and dorsum of A. craccivora. The activities of chitinase and extracellular protease were induced in the aphid after treatment with HK-1. A bioassay on A. craccivora showed that the median lethal concentration (LC₅₀) of the fungus crude extract was 24.00 mg mL⁻¹ for 24 h of treatment. Additionally, the results showed that the crude extract disrupted the enzyme system of A. craccivora, inducing the inhibition of carboxylesterase (CarE) and the induction of glutathione S-transferase (GST) and acetylcholinesterase (AChE). Combining these results with those of a gas chromatography–mass spectrometry (GC-MS) analysis, it is suggested that p-cymene, hymecromone, 9,12-octadecadienoic acid (Z, Z) methyl ester, and 9,12-octadecadienoic acid (Z, Z) may be connected to the insecticidal effects we observed. This study provides a theoretical basis for the use of L. araneicola HK-1 as a potential biological control agent.

The beet armyworm Spodoptera exigua (Hübner), a global pest, feeds on and affects a wide range of crops. Its long-distance migration with the East Asian monsoon frequently causes large-scale outbreaks in East and Southeast Asia. This pest mainly breeds in tropical regions in the winter season every year; however, few studies have investigated associations with its population movements in this region. From 2017 to 2023, we monitored its population dynamics in a tropical site, located in Hainan Province of China, using a searchlight trap. Dissection of the ovaries of female S. exigua moths captured from the air revealed that most of them were reproductively mature and could be classified as a transit migratory population. Migration occurred most often in summer and least often in winter, with an increasing trend over the years. According to a trajectory model analysis based on the Weather Research and Forecasting (WRF) model, S. exigua migrated from Hainan Island to mainland China in the spring, primarily moved from the areas of Southeast Asia to Hainan and mainland China during the summer, and returned from China to Southeast Asia in the autumn and winter. Overall, our research defines the movement paths of S. exigua in the tropical area of China, establishing a theoretical foundation for its regional monitoring, early warning, and management in China and Southeast Asian countries.

Chelonus formosanus is a parasitic wasp capable of parasitizing various Noctuidae pests, including the highly invasive Spodoptera frugiperda, and it demonstrates strong pest control potential. Both egg and larval stages primarily occur within the host organism, and the total developmental time from egg to adult is approximately 19.62 days. To investigate the microbial communities at different stages, we performed 16S rDNA sequencing (V1–V9 region) using PacBio sequencing and identified 404 bacterial species belonging to 61 classes, 116 orders, 182 families, and 308 genera across larval, pupal, female, and male adult stages. Bacterial diversity and richness varied across the stages, with Enterobacter and Enterococcus dominating in larvae and pupae and Pseudomonas emerging as dominant in female adults. In contrast, male adults predominantly resided with Ralstonia and Achromobacter. The predicted functions of bacteria within C. formosanus at different developmental stages are predominantly marked by the high abundance of metabolic pathways. This study provides a comprehensive understanding of the morphology of C. formosanus and contributes to the practical control of host pests. Additionally, our findings preliminarily characterized the microbial community of various developmental stages, laying the groundwork for its functional study.

In this study, the migratory agricultural pest Spodoptera frugiperda was exposed to three periodic short-term heat stress regimes at 37 °C, 40 °C, and 43 °C (2 h daily), with a constant 26 °C control. We systematically evaluated the effects of periodic thermal stress on developmental traits across all life stages. Combined with 16S rRNA high-throughput sequencing, we analyzed the structural and functional characteristics of the gut bacterial community in adults under heat stress. The results demonstrated that 37 °C exposure accelerated egg-to-adult development, whereas 43 °C markedly extended it. Additionally, 43 °C heat stress suppressed pupation and eclosion rates. Increasing stress temperatures were negatively correlated with pupal weight and body size in both sexes. Notably, 43 °C heat stress caused complete loss of hatching ability in offspring eggs, thereby rendering population reproduction unattainable. 16S rRNA sequencing revealed that Proteobacteria (>90%) dominated the gut bacterial community at the phylum level across all treatments. Under 43 °C heat stress, although female and male adults exhibited an increase in specific bacterial species within their gut bacteria, Alpha diversity analysis revealed no significant differences in the diversity (Shannon index) and richness (Chao index) of gut bacterial communities between sexes under temperature treatments. PICRUSt2 functional prediction indicated that metabolic pathways, biosynthesis of secondary metabolites, and microbial metabolism in diverse environments constituted the dominant functions of gut bacteria in both sexes, while heat stress exerted minimal effects on the functional profiles of gut bacteria in S. frugiperda. These findings not only provide a theoretical basis for predicting summer population dynamics and formulating ecological control strategies for S. frugiperda but also offer critical insights into the adaptive interactions between this pest and its gut bacterial community under heat stress. The results lay a foundation for further exploring the interactions between insect environmental adaptability and bacterial symbiosis.

To provide a scientific basis for pest control, this study evaluated the insecticidal activity of novaluron against the fall armyworm (Spodoptera frugiperda) and diamondback moth (Plutella xylostella). The leaf-dip method determined the toxicity of novaluron to second-instar larvae, while corn leaves and cabbage treated with sublethal (LC₁₀) and median lethal concentrations (LC₅₀) of novaluron were used to feed the larvae. Enzyme-linked immunosorbent assays (ELISA) measured the activities of detoxifying enzymes [carboxylesterase (CarE), cytochrome P450 (P450), glutathione S-transferase (GST), and acetylcholinesterase (AChE)] and ecdysteroid (Ecd) levels in the pests after 24 and 48 h of treatment. Results indicated that after 24 h, AChE was involved in diamondback moth metabolism and CarE activity was inhibited. After 48 h, P450 and GST participated in fall armyworm detoxification, whereas P450 and GST were active in diamondback moth detoxification, with other enzyme activities normalizing. Novaluron also altered Ecd levels in both pests. These results demonstrate differing detoxification mechanisms in fall armyworm and diamondback moth, likely due to their unique physiological and ecological traits, and support the potential use of novaluron in pest management strategies.