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The red imported fire ant Solenopsis invicta Buren (Hymenoptera: Formicidae) is native to South America; however, its introduction to other countries has caused serious biodiversity, agricultural, and public health problems. As toxic bait is an effective method to control fire ant populations, the aim of this study was to determine the most effective concentration of sulfoxaflor, flupyradifurone, and triflumezopyrim as ingredients for baits against S. invicta under laboratory and field conditions. Sulfoxaflor, flupyradifurone, and triflumezopyrim had no effect on the feeding behavior of the fire ants. However, they significantly reduced the climbing, walking, and arrest abilities of the fire ant workers after 10 days of treatment, and insecticides were horizontally transferred from workers to alates or larvae. Specifically, sulfoxaflor and triflumezopyrim at 0.05% concentration were the most effective in exterminating fire ants. Sulfoxaflor and triflumezopyrim are nonrepellent and effective insecticides against S. invicta.

Bactrocera dorsalis is a highly invasive and destructive pest distributed worldwide. Chemical insecticides remain the primary measure for their control; however, this species has already developed resistance to several insecticides. In recent years, there have been several reports of monitoring B. dorsalis resistance in China, but continuous monitoring results are lacking and do not even span a decade. In this study, we monitored the dynamics of resistance to seven insecticides among 11 geographically distinct Chinese populations of B. dorsalis (2010–2013; follow-up in 2023). The 11 populations were found to adapt rapidly to antibiotic insecticides (spinosad, emamectin benzoate, and avermectin), reaching high levels of insecticide resistance in several areas. Overall, a decreasing trend in resistance to organophosphorus insecticides (chlorpyrifos and trichlorfon) was observed, whereas pyrethroid (beta-cypermethrin and cyhalothrin) resistance trends were observed to both increase and decrease. The monitoring of field resistance among different B. dorsalis populations over the duration of this study is important for improving the efficiency and sustainability of agricultural pest management, and the results provide a scientific basis for the development of more effective resistance management strategies.

Bactrocera dorsalis (Hendel) (Diptera: Tephritidae) is a global economic pest that poses a serious threat to the fruit industry. In the southwest of China, Yunnan Province sustains a severe infestation of B. dorsalis. An automated monitoring system designed for B. dorsalis was employed in this study to elucidate the annual population dynamics of B. dorsalis in four counties: Yuanjiang, Huaping, Guangnan, and Ludian in Yunnan. The system utilizes sex parapheromone and image recognition technology. The data uploaded by the device are used to analyze the annual population dynamics of B. dorsalis in different regions. The results showed that the populations of adult B. dorsalis in all four counties peaked twice annually, with Yuanjiang experiencing the earliest peak periods, followed by Huaping, Guangnan, and Ludian. Adult B. dorsalis occurred in Yuanjiang throughout the year, and Yuanjiang had the highest number of B. dorsalis monitored. In Huaping, adult B. dorsalis occurred in March–December and was highly active, with a high population density in 2019. Bactrocera dorsalis did not occur in December in Guangnan but only in May–October in Ludian. Bactrocera dorsalis abundance was correlated with temperature in all four areas. The outcomes of this experiment provide a practical foundation for developing control strategies targeting B. dorsalis in various orchards across each county.

Diptera and Lepidoptera species have the highest levels of insecticide resistance, and the mechanism of drug resistance has been studied in detoxification metabolism genes such as P450, GST, EST, and ABC. Since Bactrocera dorsalis are resistant to a variety of chemicals, the pattern and mechanism of resistance in Bactrocera dorsalis have been investigated from a variety of aspects such as detoxification metabolism genes, detoxification enzymes, intestinal symbiotic bacteria, and synergists in the world. In this study, 51 species and 149 detoxification metabolism genes were annotated in the Suppression Subtractive Hybridization (SSH) library, and 12 candidate genes related to beta-cypermethrin resistance were screened and quantitatively expressed in this library. Two genes were found to be upregulated in the egg stage, three genes in the larval stage, one gene in the pupal stage, and five genes in the adult stage, and four genes were found to be upregulated in the midgut and the malacca ducts in the midgut. The expression of cyp6g1, cyp6a22, GST-Epsilon9, and Trypsin-4 genes was upregulated in resistant strains, with the most obvious upregulation occurring in the midgut and the Malpighian tubules. These results provide new insights into the study of pesticide resistance in quarantine insects.

How alien pests invade new areas has always been a hot topic in invasion biology. The spread of the Bactrocera dorsalis from southern to northern China involved changes in food sources. In this paper, in controlled conditions, we take Bactrocera dorsalis as an example to study how plant host transformation affects gut bacteria by feeding it its favorite host oranges in the south, its favorite host peaches and apples in the north, and feeding it cucumbers as a non-favorite host plant, thereby further affecting their fitness during invasion. The result showed that, after three generations of feeding on cucumbers, Bactrocera dorsalis took longer to develop as a larva while its longevity and fecundity decreased and pre-adult mortality increased. Feeding it cucumbers significantly reduced the overall diversity of gut microbiota of Bactrocera dorsalis. The relative abundance of Enterobacter necessary for survival decreased, while the Empedobacter and Enterococcus increased, resulting in decreased carbohydrate transport and metabolism and increased lipid transport and metabolism. Feeding Bactrocera dorsalis Empedobacter brevis and Enterococcus faecalis resulted in a 26% increase in pre-adult mortality and a 2–3 d increase in adult preoviposition period (APOP). Additionally, Enterococcus faecalis decreased the longevity of female and male adults by 17 and 12 d, respectively, and decreased fecundity by 11%. We inferred that the shifted plant hosts played an important role in posing serious harm to Bactrocera dorsalis invading from the south to the north. Therefore, after an invasion of Bactrocera dorsalis into northern China, it is difficult to colonize cucumbers for a long time, but there is still a risk of short-term harm. The findings of this study have established that the interactions between an insect’s food source and gut bacteria may have an important effect on insect invasions.

Fruit flies cause substantial economic damage, and their management relies primarily on chemical insecticides. However, pesticide resistance has been reported in several fruit fly species, the mitigation of which is crucial to enhancing fruit fly control. Here, we assess the toxicity of a novel insecticide (fluralaner) and a common insecticide (dinotefuran) against three fruit fly species, Bactrocera dorsalis (Hendel), Bactrocera cucurbitae (Coquillett), and Bactrocera tau (Walker). Both pesticides exhibit robust lethal and sublethal effects against all three fruit fly species, with fluralaner being more potent. Fluralaner and dinotefuran suppress the reproductive capacities and survival rates of fruit flies. However, at the 50% lethal concentration, fluralaner stimulates the reproductive capacity of B. dorsalis and the survival rate of B. tau. Fluralaner also causes significant transgenerational effects, impacting the offspring hatching rate of B. cucurbitae and B. tau and reducing the proportion of female offspring. Thus, both pesticides exhibit high potential for controlling fruit flies. However, their application should be tailored according to species variations and the diverse effects they may induce. Collectively, the findings of this study outline the sublethal effects of two insecticides against fruit flies, helping to optimize their application to ensure the effective management of insecticide resistance.

Bactrocera dorsalis (Hendel) (B. dorsalis) is an important agricultural invasive pest that causes significant economic losses in tropical and subtropical fruit and vegetable crops. In this study, the proteins related to the sense of smell and taste of B. dorsalis, such as OBP, PBP, OR, IR, SNMP and CSP, were screened based on B. dorsalis transcriptome data. By integrating the compounds that were reported to be attractive to B. dorsalis, similar compounds of hydrocarbon compounds were obtained. Molecular docking was used to predict the binding between the similar compounds and the OBP, PBP, OR, IR, SNMP and CSP proteins. Network pharmacology was used to screen the potentially attractive compounds, and ecological experiments with B. dorsalis were finally conducted to verify the effect of these potentially attractive compounds on B. dorsalis. The results showed that the G protein-coupled receptor [BR: KO04030] and ion channel [BR: KO04040] pathways were closely related to the odor tropism of B. dorsalis. A total of 84 compounds, such as mitemcinal, exemestane and midecamycin, have potential binding effects on the B. dorsalis odor receptor proteins. The results of the ecological experiments showed that 1 mg/mL and 0.1 mg/mL 19-norandrostenedione, 1 mg/mL progesterone compounds was significantly attractive to B. dorsalis males, while 0.1 mg/mL exemestane was significantly attractive to B. dorsalis females. In this study, network pharmacology technology was used to discover the potential attractive compounds for B. dorsalis, which is important for the development and subsequent prevention and control of B. dorsalis. It can provide a reference in improving the success rates of clinical trials of new pest control products and in reducing the time and cost of drug development.

The injudicious and excessive use of synthetic pesticides has deleterious effects on humans, ecosystems, and biodiversity. As an alternative to traditional crop-protection methods, botanical pesticides are gaining importance. In this research endeavor, we examined the contact toxicity, knockdown time, lethal time, and toxicity horizontal transmission of three natural pesticides from plants (azadirachtin, celangulin, and veratramine) on red imported fire ants (RIFA; Solenopsis invicta). Our research findings indicated that azadirachtin and celangulin exhibited relatively high toxicity, with median lethal dose (LD50) values of 0.200 and 0.046 ng/ant, respectively, whereas veratramine exhibited an LD50 value of 544.610 ng/ant for large workers of S. invicta at 24 h post-treatment. Upon treatment with 0.125 mg/L, the (median lethal time) LT50 values of azadirachtin and celangulin were determined to be 60.410 and 9.905 h, respectively. For veratramine, an LT50 value of 46.967 h was achieved after being tested with 200 mg/L. Remarkably, azadirachtin and celangulin were found to exhibit high horizontal transfer among RIFA, with high secondary mortality (100%) and tertiary mortalities (>61%) after 48 h of treatment with 250 mg/L, as well as with their dust formulations for 72 h. However, veratramine did not exhibit significant toxicity or horizontal transfer effects on RIFA, even at high concentrations. These findings suggest that azadirachtin and celangulin are likely to have a highly prominent potential in the management of S. invicta.

Bactrocera dorsalis (Hendel, 1912) (Diptera: Tephritidae), commonly known as the oriental fruit fly, is a highly destructive pest that globally infests fruits and vegetables, resulting in significant annual economic losses. Initially detected in Taiwan Island, it has rapidly expanded its distribution range to various regions in mainland China since the 1980s, with a continuous northward spread. To mitigate the damage caused by this pest, extensive efforts have been undertaken to comprehend its ecological and physiological adaptations and develop management strategies. This review article provides an overview of the invasion history of B. dorsalis in China, its ecological and physiological mechanisms facilitating its invasion, and the progress made in understanding its major biological characteristics. Moreover, the key approaches for managing B. dorsalis that have been or are likely to be implemented in China are presented, including quarantine measures, monitoring procedures, physical controls, biological controls, the sterile insect technique, RNA interference, and CRISPR-Cas-9. Finally, some suggestions for future research directions are provided.

Long non-coding RNAs (lncRNAs) represent a class of RNA molecules that do not encode proteins. Generally studied for their regulatory potential in model insects, relatively little is known about their immunoregulatory functions in different castes of eusocial insects, including Solenopsis invicta, a notoriously invasive insect pest. In the current study, we used Metarhizium anisopliae, an entomopathogenic fungus, to infect the polymorphic worker castes (Major and Minor Workers) and subjected them to RNA sequencing at different intervals (6, 24, and 48 h post-infection (hpi)). Comprehensive bioinformatic analysis identified 5719 (1869 known and 3850 novel) lncRNAs in all libraries. Genomic characteristics analysis showed that S. invicta lncRNAs exhibited structural similarities with lncRNAs from other eusocial insects, including lower exon numbers, shorter intron and exon lengths, and a lower expression profile. A comparison of lncRNAs in major and minor worker ants revealed that several lncRNAs were exclusively expressed in one worker caste and remained absent in the other. LncRNAs such as MSTRG.12029.1, XR_005575440.1 (6 h), MSTRG.16728.1, XR_005575440.1 (24 h), MSTRG.20263.41, and MSTRG.11994.5 (48 h) were only present in major worker ants, while lncRNAs such as MSTRG.8896.1, XR_005574239.1 (6 h), MSTRG.20289.8, XR_005575051.1 (24 h), MSTRG.20289.8, and MSTRG.6682.1 (48 h) were only detected in minor workers. Additionally, we performed real-time quantitative PCR and experimentally validated these findings. Functional annotation of cis-acting lncRNAs in major worker ants showed that lncRNAs targeted genes such as serine protease, trypsin, melanization protease-1, spaetzle-3, etc. In contrast, apoptosis and autophagy-related genes were identified as targets of lncRNAs in minor ants. Lastly, we identified several lncRNAs as precursors of microRNAs (miRNAs), such as miR-8, miR-14, miR-210, miR-6038, etc., indicating a regulatory relationship between lncRNAs, miRNAs, and mRNAs in antifungal immunity. These findings will serve as a genetic resource for lncRNAs in polymorphic eusocial ants and provide a theoretical basis for exploring the function of lncRNAs from a unique and novel perspective.

The red imported fire ant (Solenopsis invicta Buren, 1972) is a globally significant invasive species, causing extensive agricultural, human health, and biodiversity damage amounting to billions of dollars worldwide. The pathogenic fungus Metarhizium anisopliae (Metchnikoff) Sorokin (1883), widely distributed in natural environments, has been used to control S. invicta populations. However, the interaction between M. anisopliae and the immune system of the social insect S. invicta remains poorly understood. In this study, we employed RNA-seq to investigate the effects of M. anisopliae on the immune systems of S. invicta at different time points (0, 6, 24, and 48 h). A total of 1313 differentially expressed genes (DEGs) were identified and classified into 12 expression profiles using short time-series expression miner (STEM) for analysis. Weighted gene co-expression network analysis (WGCNA) was employed to partition all genes into 21 gene modules. Upon analyzing the statistically significant WGCNA model and conducting Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis on the modules, we identified key immune pathways, including the Toll and Imd signaling pathways, lysosomes, autophagy, and phagosomes, which may collectively contribute to S. invicta defense against M. anisopliae infection. Subsequently, we conducted a comprehensive scan of all differentially expressed genes and identified 33 immune-related genes, encompassing various aspects such as recognition, signal transduction, and effector gene expression. Furthermore, by integrating the significant gene modules derived from the WGCNA analysis, we constructed illustrative pathway diagrams depicting the Toll and Imd signaling pathways. Overall, our research findings demonstrated that M. anisopliae suppressed the immune response of S. invicta during the early stages while stimulating its immune response at later stages, making it a potential biopesticide for controlling S. invicta populations. These discoveries lay the foundation for further understanding the immune mechanisms of S. invicta and the molecular mechanisms underlying its response to M. anisopliae.

The massive use of synthetic pesticides to manage agricultural pests results in environmental pollution and health hazards. The secondary plant metabolites, which are majorly dominated by terpenoids, have the potential to be developed into novel alternatives to synthetic chemicals. Therefore, in our current investigation, six majorly dominated essential oil constituents were evaluated for their toxicity against adults and immature stages of oriental fruit flies, Bactrocera dorsalis, a worldwide fruit pest. The results indicated that carvacrol was the most toxic essential oil constituent (EOC) to adult flies, with LC50 of 19.48 mg/mL via fumigant assay, followed by thujone 75% mortality via ingestion toxicity test against adult fruit flies. Similarly, when larvae were dipped in different concentrations of EOCs, carvacrol appeared as the most toxic EOC with the lowest LC50 (29.12 mg/mL), followed by (−)-alpha-pinene (26.54 mg/mL) and (R)-(+)-limonene (29.12 mg/mL). In the oviposition deterrence tests, no egg was observed on oranges seedlings treated with 5% of each EOC (100% repellency). Regarding the repellency assay, a significantly higher number of flies (77%) were repelled from the Y-tube olfactometer arm containing (−)-alpha-pinene, followed by carvacrol (76%). Our results showed that the selected essential oil constituent has the potential to be developed as an alternative to synthetic pesticides against B. dorsalis. However, further research is required to assess the activities of these EOCs under open-field conditions.

Bactrocera tau (Walker) (Diptera: Tephritidae) is a serious, economically important invasive pest that has spread and been established in many regions worldwide. Temperature is a crucial abiotic factor governing insect activity, fitness, and geographical distribution. Yet, surprisingly, the tolerance of B. tau to extreme cold and heat stress remains unclear. Here, we measured the supercooling point (SCP) of different life stages of B. tau. Further, several life stages of B. tau (egg, 1st, 2nd, and 3rd instar larvae, 1-day-old pupae, and 3-day-old adult) were subjected to six low temperatures (−9, −7, −5, −3, −1, and 0 °C) and six high temperatures (39, 40, 41, 42, 43, and 44 °C) for various durations (0.5, 1.0, 2.0, and 4.0 h), and three-way survival–time–temperature relationships were investigated. We found that the SCPs differed significantly among different life stages of B. tau, being the lowest for SCP of eggs, at −25.82 ± 0.51 °C. There was no significant effect of sex on the mean SCPs of B. tau adults, except for 45- to 50-day-old flies. In addition, an interaction effect was uncovered between tested temperatures and exposure duration upon B. tau mortality at different life stages. Eggs exhibited the strongest cold tolerance, yet the weakest heat tolerance. The 3rd instar larvae were the most heat- and cold tolerant among larval stages, followed by the 2nd and 1st instar larvae. The upper limit of the chill injury zone (ULCIZ) for 3-day-old adult and 1-day-old pupae was −2.51 °C and −2.50 °C, respectively, while their corresponding lower limit of thermal injury zone (LLTIZ) was 39.39 °C and 38.29 °C. This paper presents valuable data to provide an integrated knowledge for understanding the cold and heat tolerance potential of B. tau and ensure the proper implementation of post-harvest phytosanitary protocols for this pest’s disinfestation.