【Objective】Megalurothrips usitatus is a significant vegetable pest in China, causing substantial damage to legume crops as economic plants. The purpose of this study is to compare the genetic diversity of M. usitatus in different geographical populations and ascertain the genetic differentiation of M. usitatus, and to provide a theoretical basis for the precise control of M. usitatus. 【Method】A total of 18 geographical populations of M. usitatus were collected from 6 prefecture-level cities in Guangdong Province and 9 prefecture-level cities outside Guangdong Province. The mitochondrial DNA (mtDNA) cytochrome c oxidase subunit 1 (CO1) gene sequence was obtained based on PCR. The haplotype diversity (Hd), nucleotide diversity (π) of different geographical populations were analyzed, and Tajima’s D neutrality test based on the mtCO1 was performed to evaluate the genetic structure of M. usitatus populations across different geographical regions. The fixation index (FST) and gene flow (Nm) were calculated to evaluate the degree of genetic differentiation among populations. 【Result】A total of 111 mtCO1 gene sequences were detected in 18 geographical populations of M. usitatus. A total of 617 conserved sites and 24 variable sites were detected, accounting for 3.68% of the total sequence length. A total of 20 haplotypes (H1-H20) were detected, of which H4 was the dominant haplotype, accounting for 48.6% of the total sequence and distributed in 17 populations. The overall population of M. usitatus exhibited relatively high haplotype diversity (Hd=0.677) and nucleotide diversity (π=0.00425), but nucleotide sequence divergence among different genetic types was not pronounced. The nonsignificant Tajima’s D neutrality test indicated stable population size without marked expansion. Furthermore, the population fixation coefficient (FST=0.04973<0.05) and gene flow (Nm=9.55>1) suggested sufficient genetic exchange and low genetic differentiation among geographically distinct populations. The results of molecular variance analysis showed that the main factor causing the overall population variation was intra-population variation. 【Conclusion】The geographically distinct populations of M. usitatus exhibited relatively high genetic diversity, with frequent gene flow and minimal genetic differentiation among populations, suggesting a stable overall population size. These findings provide a theoretical basis for the integrated management of M. usitatus field populations in diverse regions.
【Objective】The objective of this study is to investigate the disruptive effect of acoustic stimuli on the courtship behavior of Liriomyza sativae and its application potential in green pest control. 【Method】Acoustic signals of varying frequencies were emitted by directional loudspeakers. Laser vibrometry coupled with behavioral video recording was employed to measure vibrational responses of cowpea leaves and courtship and mating parameters of L. sativae (latency, frequency, duration, mating success rate). The laboratory population control trial of L. sativae larvae was carried out by using 200 Hz acoustic frequency, and the population density change of L. sativae and effect on cowpea quality (soluble sugar, soluble protein and vitamin C content) were analyzed by setting sound source distance gradient with spatiotemporal dynamic monitoring in the field. 【Result】External acoustic stimulation induced differential leaf vibrational responses, disrupting L. sativae courtship. Cowpea leaves exhibited the strongest vibrational response within 200-300 Hz with peak vibration velocity of ±4 mm·s-1. The 200 Hz frequency significantly prolonged male courtship latency ((15.92±3.99) min vs. control (5.24±1.63) min, P<0.05) and duration ((44.50±2.68) s vs. control (20.22±1.97) s, P<0.05), increased male courtship attempts ((13.20±2.58) times vs. control (5.40±1.21) times, P<0.05), and reduced mating success rate to 20% (control: 60%). Markov chain analysis confirmed greatest behavioral disruption in the mid-frequency band (200-300 Hz), specifically blocking the critical “male courtship→female response” transition pathway. Laboratory trials demonstrated 42.14% larval number reduction under 200 Hz acoustic treatment ((57.67±3.18) individuals vs. control (99.67±9.61) individuals, P<0.05). Field data indicated that with the increase of audio playback time, the mining density in near-source zones (0-25 m) decreased significantly, though efficacy diminished in far-source areas (25-70 m). No significant adverse effects occurred on cowpea quality parameters (soluble sugar, soluble protein and vitamin C content). 【Conclusion】The 200 Hz acoustic frequency disrupts L. sativae courtship signaling by maximizing cowpea leaf vibrations, effectively suppressing mating behavior and population growth without compromising crop quality. This technique provides an innovative perspective for developing environmentally-friendly pest control strategies.
【Objective】Megalurothrips usitatus is a major biotic disaster for leguminous crops, particularly prone to damaging cowpeas. The study aims to clarify the relationship between field population dynamics of M. usitatus and cowpea flowers, and to develop new green control technologies. 【Method】The population dynamics of M. usitatus across different growth stages and plant organs of cowpeas were investigated, along with the influence of flower opening and shedding times on their activity patterns. The optimal timing for pesticide application was determined, and the abscission efficiency of five abscission methods (natural abscission, fan-induced abscission, lever-induced abscission, climbing net-induced abscission, and a combined method using both fan and lever) was compared. Additionally, the effectiveness of various flower-absorbing carriers (silver-gray plastic film, shading net, weed-proof fabric, hundred-knot net, and bare soil) was evaluated. Based on these findings, a novel integrated green control strategy, termed the “trinity, internal and external killing” approach, was developed and assessed for its efficacy in controlling M. usitatus, as well as its impact on cowpea quality and yield. 【Result】The population density of M. usitatus exhibited a trend of initial increase followed by a decline from the seedling stage to the end of flowering. The lowest population density was observed during the seedling stage, with a significant increase noted during the early flowering stage, peaking at full flowering stage. M. usitatus adults predominantly reside within flowers, while nymphs preferentially inhabit pods, followed by flowers and tender shoots. As flower buds open, the number of M. usitatus adults within flowers increases progressively. Flower closure typically occurs after 10: 00, encapsulating the insects within the floral structures. These closed flowers generally fall off gradually the following day; however, substantial numbers of M. usitatus remain concealed within the fallen flowers. Notably, flowers with receptacles harbor significantly higher numbers of M. usitatus compared to those without. A mass exodus of M. usitatus from the floral structures typically begins after 6: 00, at which point they migrate to new plant organs. For effective chemical control, application during the evening or early morning—when flowers are open—is most effective. Among the tested abscission methods, the combined use of a fan and lever demonstrated the highest efficiency in removing flowers. Additionally, the hundred-knot net significantly enhanced the effectiveness of flower collection. The implementation of the “trinity, internal and external killing” integrated green control strategy resulted in a 93.71% reduction in black head and black tail symptoms, a 96.87% reduction in wrapper tail, and a 91.55% reduction in overall malformation in cowpeas, accompanied by a 20.40% increase in yield. 【Conclusion】The “trinity, internal and external killing” technique not only challenges the conventional reliance on chemical pesticides, but also effectively suppresses M. usitatus populations, enhances cowpea quality and yield, and provides a valuable theoretical and practical framework for the development of green pest control strategies in other crops.
【Objective】The objective of this study is to evaluate the control effect of a new type of insect-repellent screen on Megalurothrips usitatus, and to clarify its effect on the microclimate environment in the field, so as to provide new technical support for the control of cowpea thrips. 【Method】The barrier effects of a new type of insect-repellent screen and conventional insect-proof screen on M. usitatus were investigated under laboratory and field conditions. Light intensity, ventilation, temperature, and humidity were measured using the illuminometer, anemometer, and thermo-hygrometer, respectively, under three treatments of insect-repellent screen, conventional insect-proof screen and open field. The effect of insect-repellent screen on the field microclimate was further analyzed based on the observed data. Gas chromatography-mass spectrometry (GS-MS) was employed to detect the types, contents of insect-repellent volatile compounds in the screen after two months of field application. 【Result】The laboratory results showed that the barrier rate of the new insect-repellent screen cage against M. usitatus adults generally exhibited a slowly declining trend within one month. The barrier rate of the insect-repellent screen was 52.81%-67.11%, significantly higher than that of the conventional insect-proof screen (46.32%-51.23%). Field results indicated that within one month of investigation during the flowering and pod-setting stage of cowpeas, the adult populations of M. usitatus in the insect-repellent screen, conventional insect-proof screen (both with a porosity of 69.40%), and open field were 4.3-7.4, 6.2-11.1 and 7.8-14.2 individuals/flower, respectively. The overall trend of population in the insect-repellent screen remained at a lower level, significantly lower than that in the conventional insect-proof screen and open-field cowpeas. No significant differences were observed among the three treatments (insect-repellent screen, conventional insect-proof screen, and open field) in terms of light intensity (11 900-73 800, 11 400-73 100, and 12 000- 73 900 lx, respectively), wind speed (0.16-1.38, 0.12-1.39, and 0.20-1.47 m·s-1, respectively), daily mean temperature (18.73-25.75, 19.50-25.62, and 19.51-26.00 ℃, respectively), and daily mean relative humidity (65.00%-72.15%, 66.32%-73.78%, and 62.10%-69.66%, respectively). During a single day at the full blooming stage of cowpea, the temperature and relative humidity under all three treatments exhibited an inverted “U”-shaped and a positive “U”-shaped trend, respectively. Specifically, the temperature reached the highest value in the afternoon (13: 00-16: 00), while the relative humidity dropped to the lowest value in the afternoon (14: 00-15: 00). GC-MS analysis revealed that the volatile components of the insect-repellent screen contained compounds with high similarity to menthol and limonene, with similarity scores of 79.50% and 80.00%, and the volatilization rates after two months of application were 98.47% and 92.86%, respectively. 【Conclusion】The barrier effect of the new insect-repellent screen against M. usitatus is better than conventional insect-proof screen, showing dual effects of physical barrier and biological repellence, and has negligible impact on the field microclimate environment. The development and application of the new insect-repellent screen provides a novel approach for integrated control of cowpea thrips.
【Objective】The objective of this study is to investigate the biological control effect of Bacillus velezensis SD13 against cowpea wilt when combined with different organic fertilizers, and to provide a theoretical basis for the application of biological control technology of cowpea wilt. 【Method】A pot experiment was conducted to evaluate the effects of applying 10% sheep manure, 10% vermicompost, and a 5% sheep manure+5% vermicompost mixture as fertilizer carriers on the efficacy of B. velezensis SD13 in controlling cowpea wilt. The experiment included eight treatments: blank control (CK), pathogen control (F), pathogen+SD13 (FB), pathogen+10% vermicompost (FW), pathogen+SD13+10% vermicompost (FBW), pathogen+10% sheep manure (FS), pathogen+SD13+10% sheep manure (FBS), and pathogen+SD13+5% vermicompost+5% sheep manure (FBWS). Each treatment was replicated three times, with three pots per replicate. After 45 d of cultivation in a greenhouse, the incidence rate of cowpea wilt, plant biomass (above-ground and below-ground dry weight), and defense enzyme activity (catalase) were measured for each treatment. Rhizosphere soil samples were collected, and the structure, diversity, and key microbial taxa of the soil bacterial community were analyzed using 16S rRNA high-throughput sequencing. 【Result】The control effect of sheep manure, vermicompost and mixed organic fertilizer combined with B. velezensis SD13 on cowpea wilt was more than 75%. The combination of sheep manure and SD13 significantly increased soil total nitrogen by 30%, with the dominant soil bacteria being Firmicutes, which showed a negative correlation with other bacterial communities. The combination of vermicompost and SD13 significantly increased the above-ground dry weight of diseased cowpea plants by 29% and the below-ground dry weight by 30%, enhanced the activity of catalase in cowpea by 10%, and significantly increased the richness and diversity of soil bacteria, restoring the community structure to a healthy level. The combination of mixed organic fertilizers and SD13 significantly increased the below-ground dry weight of diseased cowpea plants by 155%, with the soil community structure being influenced by the microbial communities of both vermicompost and sheep manure. 【Conclusion】The type of organic fertilizer affects the biocontrol effect of B. velezensis SD13 against cowpea wilt in the soil. Vermicompost is more suitable for combination with SD13 than sheep manure. This combination not only ensures high biocontrol effect, but also further enhances cowpea biomass, catalase activity, and soil bacterial richness and diversity. It increases the abundance of beneficial bacterial communities and restores the soil bacterial community structure and composition to levels associated with healthy cowpea soil, making it a suitable organic fertilizer for the application of SD13 in controlling cowpea wilt in soil.
【Objective】The purpose of this study is to identify the dominant species of commercial Orius species (O. nagaii, O. sauteri, O. minutus and O. strigicollis) against the main pest of cowpea Megalurothrips usitatus, Tetranychus urticae and Aphis craccivora, and to provide a scientific basis for field demonstration and commercial production of Orius species. 【Method】The single-headed female adult of a single species of Orius was used to test the predation, functional responses and search effects of different densities of M. usitatus (10, 20, 30, 40 /tube), T. urticae (5, 10, 15, 20 /dish) and A. craccivora young nymphs (5, 10, 15, 20 /dish) under indoor conditions. Holling II equation was used to analyze the predation ability and biological control potential of four Orius species on three pests. 【Result】The daily predation of four Orius species increased with the increase of the density of pests (M. usitatus, T. urticae and A. craccivora). The predatory functional response of the four Orius species conformed to the Holling II model equation, and the search effect of the four Orius species gradually decreased with the increase of prey density. While hunting M. usitatus, the transient attack rate (a′) (0.861), predation ability (a′/Th) (661.932), maximum daily predation amount (1/Th) (769.231) and processing time of single prey (Th) (0.001 d) of O. nagaii were higher than those of the other three species. While hunting T. urticae, the processing time of single prey (0.004 d), predation ability (260.617) and maximum daily predation amount (285.714) of O. nagaii were also higher than those of the other three species. There was no significant difference in the predation ability of the four Orius species on A. craccivora. 【Conclusion】At room temperature, compared with the other three Orius species, O. nagaii has better predation ability on M. usitatus and T. urticae, but the four species have little difference in predation on A. craccivora.
【Background】Megalurothrips usitatus can successfully develop and reproduce on host plants such as cowpea (Vigna unguiculata), green bean (Phaseolus vulgaris), and white bean (Vigna cylindrica), with cowpea being the most suitable host. In contrast, its development and reproductive capacity are significantly limited on wax gourd (Benincasa hispida). 【Objective】The objective of this study is to determine the digestive enzyme activity and nutrient content in M. usitatus after feeding on different hosts, and to explore the adaptation mechanism of M. usitatus to different host plants. 【Method】F1 adults of M. usitatus reared on cowpeas for 3 d were transferred to petri dishes containing cowpea, green bean, white bean, or wax gourd, with four replicates per treatment. Sampling was conducted at 0, 3, 6, 12, 24, 48, and 72 h after feeding. The dynamic changes in the activities of key digestive enzymes (including α-amylase, trehalase, trypsin, and chymotrypsin) were systematically measured. Concurrently, changes in the content of major nutrients, such as glycogen, soluble protein, and fat, were analyzed. 【Result】Significant changes were observed in the activities of digestive enzymes and the content of nutrients in M. usitatus after feeding on different host plants. The activities of various digestive enzymes in M. usitatus fed on cowpea, green bean and white bean were generally higher than those fed on wax gourd. Specifically, the α-amylase activity of M. usitatus fed on cowpea was the highest (1.33 mg·min-1·mg-1 protein), along with high trehalase activity (469.80 nmol·min-1·mg-1 protein). Trypsin and chymotrypsin activities reached 20.42 and 24.86 U·mg-1 protein, respectively. M. usitatus fed on green bean had the highest α-amylase activity (1.49 mg·min-1·mg-1 protein), but the activities of trehalase (304.81 nmol·min-1·mg-1 protein) and two proteases were slightly lower than those of cowpea group. Trehalase activity in white bean group was significantly decreased (175.61 nmol·min-1·mg-1 protein), while trypsin activity was increased (21.15 U·mg-1 protein). In contrast, all enzyme activities of M. usitatus fed on wax gourd were at the lowest level, the trehalase activity was only 152.89 nmol·min-1·mg-1 protein. Regarding nutrient content, glycogen content (1.61 mg·mg-1 protein) and fat content (5.54 μg per individual) were highest in M. usitatus fed on cowpea, while the lowest values were observed in the wax gourd group (glycogen content 0.79 mg·mg-1 protein; fat content 3.37 μg per individual). 【Conclusion】Different host plants significantly influenced the digestive enzyme activities and nutrient contents of M. usitatus. M. usitatus rapidly adjusted these physiological parameters after feeding on cowpea, green bean, and white bean, but exhibited slower adaptation on wax gourd. These findings indicate that M. usitatus has higher adaptability to cowpea, green bean, and white bean, whereas its adaptability to wax gourd is comparatively poorer.
【Objective】Megalurothrips usitatus is a persistent pest in major cowpea production areas in southern China such as Hainan. Its continuous infestation has led to a reduction in cowpea yields and quality, which has become a key biotic factor constraining the sustainable development of the industry. This study aims to provide theoretical support for cowpea thrips disaster early warning and control decision-making in tropical and subtropical cowpea-growing regions of China by systematically monitoring the annual pattern of M. usitatus in the main cowpea production area of Sanya, Hainan. 【Method】The population size of M. usitatus on host plants including Fabaceae, Cucurbitaceae, and Poaceae in Yazhou District, Sanya City, Hainan Province was investigated using the sticky trap method: August 2021 to July 2022 (the first year) and October 2023 to October 2024 (the second year). Based on the survey data, population dynamics of M. usitatus were analyzed through graphical visualization. Furthermore, by comparing population dynamic changes of M. usitatus across different years and seasons, the occurrence patterns and host transition behavior of M. usitatus on cowpea and other host plants were further analyzed. 【Result】(1) M. usitatus could cause damage on cowpeas throughout the year, and at all stages of growth. In the first year, the occurrence peaks of M. usitatus on cowpea and non-cowpea host plants occurred in winter and spring (December and January of the following year), which coincided with the peak planting period of cowpeas. In the second year, the occurrence peaks of M. usitatus on cowpeas occurred in summer and autumn (June and September), corresponding to the sporadic planting period of cowpeas. Its occurrence peaks on non-cowpea host plants occurred from early March to late April, coinciding with the large-scale crop termination period of cowpeas (pulling up seedlings after harvest). (2) M. usitatus exhibited a wide range of hosts, with significantly higher population densities on leguminous host plants (such as cowpeas, green beans, peanuts, and sesbania) than on non-leguminous host plants. (3) Studies on thrips host transfer patterns found that M. usitatus primarily infested cowpeas during the concentrated planting period of cowpea. Once cowpeas undergo large-scale crop termination (pulling up seedlings after harvest), it was likely to be transferred to the surrounding host plant plots such as eggplant, sesbania to conceal its infestation. 【Conclusion】In the Sanya region, the population density of M. usitatus on Fabaceae host plants was significantly higher than that on non-Fabaceae host plants. This pest can occur year-round in fields of cowpea, eggplant, and weeds, and exhibits the characteristic of shifting hosts to cause damage. The population dynamics of M. usitatus on cowpea and other plants show inter-annual and seasonal variations. Based on the annual population dynamic patterns of thrips in cowpea fields, it is recommended to conduct field sanitation before cowpea planting, including the removal of surrounding Fabaceae crops and weeds.
【Objective】This study aimed to identify the species composition and population dynamics of major pests in the main cowpea-producing areas of Hainan, and to evaluate the effects of different planting patterns and cultivation managements on the pest community structure, thus providing a theoretical basis for developing precise control strategies. 【Method】Systematic investigations were conducted on the pest species and dominant pests on cowpeas during the winter-spring seasons from 2020 to 2025 in Hainan cowpea planting areas, using plant visual inspection and colored sticky trap methods. The population dynamics of pests were compared under different management practices (non-pesticide-treated and conventionally pesticide-treated) and different cultivation modes (open-field, semi-enclosed, and fully-enclosed). 【Result】(1) A total of 16 pest species infesting cowpea were identified in Hainan Province, which belonged to 6 orders, 9 families. In non-pesticide-treated cowpea fields, a higher diversity of pests was observed (6 orders, 9 families, 16 species), with the dominant species being Megalurothrips usitatus, Frankliniella intonsa, Liriomyza trifolii, Spodoptera exigua, and Aphis craccivora. In contrast, conventional pesticide-treated fields exhibited reduced pest diversity (4 orders, 5 families, 10 species), with thrips and leafminers remaining as the predominant pests. (2) Regardless of pesticide application, thrips and leafminers were present throughout the entire cowpea growth cycle. Thrips populations were significantly higher, showing low numbers at the seedling stage, a continuous increase during vine elongation, and multiple population peaks during the flowering stage coinciding with bloom. Leafminers were abundant from January to March in 2021, but caused only sporadic damage during 2024-2025. (3) Under both open-field and semi-enclosed planting modes, the pest species composition was similar, primarily consisting of thrips and leafminers, with M. usitatus as the dominant thrips species and L. trifolii as the dominant leafminer species. Thrips outbreaks generally occurred around January of the following year, while spider mite outbreaks were occasionally observed in semi-enclosed planting mode in certain years. Compared with open-field and semi-enclosed modes, the species of pests in the fully-enclosed planting mode were relatively few, and only thrips accounted for approximately 66% of the total pest population. During the later growth stages under higher temperatures (i.e., January to March of the following year), populations of Bemisia tabaci and Tetranychus urticae increased significantly. In conclusion, thrips caused the most severe damage throughout the cowpea growth cycle, significantly affecting both yield and quality. In some years, leafminers and T. urticae also inflicted considerable damage, while other pests were less detrimental. 【Conclusion】There are many kinds of pests in cowpea in Hainan, among which thrips are the most serious. The occurrence of pests in open-field planting mode is more serious, and the damage of pests in net-enclosed field is relatively light. The net-enclosed mode can effectively block some pests, but the fully-enclosed planting mode is affected by the micro-environment such as high temperature and high humidity, and the probability of outbreak of B. tabaci, T. urticae and other pests in the late growth stage of cowpea is large.
