The essential oil of ‘Gannanzao’ orange peel was extracted by hydrodistillation, and the extraction conditions were optimized by Box–Behnken response surface methodology. The components of essential oil were analyzed by GC-MS. Thirty-nine different components were detected, accounting for 99.59% of the total oil. Limonene (88.07%) was the prominent component. The optimal extraction conditions were as follows: liquid material ratio of 8.4:1 (mL/g), sodium chloride concentration of 5.3%, and distillation time of 3.5 h. The Cell Counting Kit-8 assay showed that ‘Gannanzao’ orange peel essential oil had good dose-dependent inhibition effect on the proliferation of HepG2 hepatoma cells and HCT116 colorectal cancer cells. When the concentration of the essential oil was 0.6 μL/mL or higher, the viability rate of both cancer cells became lower than 13.0%. The transwell assay indicated the essential oil can inhibit migration of both cancer cells at the concentration of 0.3 μL/mL.

Microbial degradation has been considered as a rapid, green, and cost-effective technique to reduce insecticide pollutions in a contaminated environment. However, the instability and low efficacy of non-indigenous microorganisms hampers their further exploitation when being introduced into a real environmental matrix. In order to overcome the restriction that these functional microorganisms are under, we investigated the optimal conditions to improve the pyrethroid-degrading ability of one previously isolated bacterium Bacillus cereus BCC01, where 9.6% of the culture suspension (with cell density adjusted to OD₆₀₀ = 0.6) was inoculated into 50 mL media and cultivated at pH 8 and 30 °C, and its metabolic pathway was illuminated by analyzing the main metabolites via gas chromatography mass spectrometry (GC-MS). Most importantly, a key pyrethroid-hydrolyzing carboxylesterase gene estA was identified from the genomic library of strain BCC01, and then expressed in Escherichia coli BL21 (DE3). After purification, the recombinant protein EstA remained soluble, displaying high degrading activity against different pyrethroids and favorable stability over a wide range of temperatures (from 15 °C to 50 °C) and pH values (6.5–9). Therefore, the EstA-associated biodegradation of pyrethroids was determined, which could provide novel insights to facilitate the practical application of B. cereus BCC01 in the microbial detoxification of pyrethroid contamination.

The insecticides of microbial origin may be promising biocontrol agents to control pests. In this study, a major metabolite was extracted and purified from Serratia marcescens KH-001 and identified as prodigiosin with a molecule weight of 324.2094, and our primary aim was to evaluate the effects of prodigiosin against Diaphorina citri Kuwayama (Hemiptera: Liviidae) in the laboratory and in the field. Toxicity of purified prodigiosin to nymphs increased with increasing temperature from 25 to 35°C. The laboratory experiment results observed inhibition effects of purified prodigiosin at LC₅₀ on oviposition and egg hatch of D. citri at 30°C. Furthermore, adults that fed on citrus leaves treated with LC₂₀ and LC₅₀ solution of purified prodigiosin at 30°C excreted less honeydew (28–35%) compared with controls, suggesting moderate antifeedant activity of prodigiosin. The results of field experiment showed that 10% prodigiosin emulsifiable concentrate exhibited better control efficacy (70–100%) at three concentrations (100, 200, and 500 mg/liter) in July and August than in October. These data indicate that prodigiosin will be a highly effective compound for the control of D. citri depending on the prevailing temperature conditions and may become a commercially available product to be widely used in citrus orchards.

Asian citrus psyllid (ACP), Diaphorina citri (Hemiptera: Liviidae), is one of the most devastating pests in citrus orchards due to its role in transmitting Huanglongbing (HLB). Currently, chemical control remains the most effective strategy for ACP management. Mineral oils are commonly used as insecticides or adjuvants in integrated pest management (IPM) practices. To extend the product life of synthetic pesticides, we evaluated the toxicity of chlorpyrifos (CPF), thiamethoxam (THX), or pyriproxyfen (PPF) mixed with mineral oil Lvying (LY) against ACP nymphs under different weather conditions. Individual application of CPF, THX, and PPF effectively controlled against ACP nymphs under no rain conditions, with mortality rates varying from 20 to 100% during 1–5 d after treatment. The addition of LY at 1.0% or 0.5% rates to CPF, THX, and PPF significantly enhanced their control efficacy, achieving sustained mortality rates from 60 to 100% during the same period. Light rain had less impact on the control efficacy of these insecticide mixtures compared to individual insecticides. However, cumulative rainfall above 20 mm significantly reduced the control efficacy of individual insecticides and their mixtures. The addition of LY decreased both surface tension and contact angle of THX solution on citrus leaves, thereby enhancing the solution’s wetting and increasing THX deposition. Moreover, the rainfastness of THX was improved after adding LY, leading to a greater retention on the leaves. LY at a rate of 1.0% exhibited excellent efficacy against ACP nymphs, and observations using scanning electron microscopy (SEM) showed that LY altered ACP mouthpart morphology and blocked spiracles, likely contributing to its insecticidal effects. This study revealed that mineral oils can serve as both insecticides to combine with synthetic pesticides for enhancing toxicity against ACP and as adjuvants to facilitate the deposition and rainfastness of synthetic pesticides on leaves, which could be recommended for sustainable ACP management in citrus orchards.

Diaphorina citri is one of the most destructive pests to global citrus production. Chemical control through insecticide application has traditionally served as the primary intervention strategy for suppressing D. citri populations. However, recent field observations from China have indicated diminishing control efficacy, suggesting potential resistance development. This study assessed insecticide resistance in 10 D. citri field populations from major citrus-producing provinces across the Guangxi–Hunan–Jiangxi region and characterized transcriptomic changes. Bioassays against 6 insecticides revealed variable resistance profiles. Chlorpyrifos resistance ranged from 9- to 16-fold across 9 of 10 populations, with Huichang showing the highest ratio (16-fold). The Ganxian population showed 6.1-fold thiamethoxam, 8.3-fold imidacloprid, and 14-fold chlorpyrifos resistance. Resistance to dinotefuran (0.75 to 3.2-fold), clothianidin (0.47 to 2.2-fold), and lambda-cyhalothrin (0.95 to 4.7-fold) remained low across all populations, as did resistance in the Nanfeng population to all 6 insecticides (RR₅。 = 0.47 to 2.7). Comparative transcriptomic analysis between the resistant Ganxian and minimally resistant Nanfeng populations revealed distinct gene expression profiles. In the Ganxian population, 19 cytochrome P450 genes, 3 glutathione S-transferase genes, and 1 UDP-glycosyltransferase gene were upregulated, and gene ontology enrichment analysis identified significant enrichment of oxidoreductase activity (false discovery rate < 0.05). Quantitative real-time polymerase chain reaction validation across 4 populations confirmed that CYP4C1, GSTT1, and UGT2B9 expression was broadly consistent with resistance phenotypes, though these associations remain correlative pending functional validation. These findings provide region-specific baseline data to support targeted, population-specific resistance management for D. citri in one of China’s most important citrus-producing regions.