Browsing by Author "He X"
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- ItemAge and Density of Mated Females Affect Dispersal Strategies in Spider Mite Tetranychus ludeni Zacher(MDPI AG, 2024-05-20) Zhou P; He X; Chen C; Wang QAbstract: The dispersal strategies of a species can affect its invasion success. Investigations into the dispersal strategies of invasive species in relation to different factors help improve our understanding of invasion mechanisms and provide knowledge for population management and invasion evaluation. Tetranychus ludeni Zacher (Acari: Tetranychidae) is an invasive species which is native to Europe but is now cosmopolitan. Here, we examined the effects of age and density on dispersal in mated females. Our results show that older females that are capable of producing more eggs within 24 h were more likely to disperse and moved longer distances than younger ones with fewer eggs. Older females spread most of their eggs out of their natal habitats and over longer distances, which reduced competition and increased offspring fitness. Females exhibited significantly increased dispersal probability and distances with an increase in population density to avoid crowding. The synchronization of dispersal and reproduction, along with the positive density-dependent dispersalstrategy, may facilitate the habitat colonization and invasion speed of T. ludeni.
- ItemHigh-pressure processing of bovine milk: Effects on the coagulation of protein and fat globules during dynamic in vitro gastric digestion(Elsevier B V, 2022-09-15) He X; Yang M; Yuan F; Singh H; Ye A; Sun QThe effect of high-pressure processing (HPP) on the digestion behavior of skim and whole bovine milks was investigated using a human gastric simulator. Both milks formed clots during gastric digestion. HPP treatment led to the formation of a coagulum with a fragmented and crumbled structure, compared with the coagulum formed from untreated milk. At pressures over 400 MPa, more intense pressure resulted in looser and more fragmented gastric clot structures. The weight of the dried clots and the moisture content in the clots of the skim milk treated at 600 MPa were significantly lower and higher than that of untreated skim milk, respectively. The looser and more fragmented gastric clot structures consequently led to faster hydrolysis of the proteins by pepsin during gastric digestion. The denaturation of the whey proteins induced by HPP may have also altered the resistance of α-lactalbumin and β-lactoglobulin in the HPP-treated milk samples to pepsin hydrolysis. This study provides insights into the differences among untreated skim milk, untreated whole milk and HPP-treated milk under in vitro gastric digestion conditions. The structure of the clots formed in the gastric environment affects their breakdown and consequently their emptying rate into the intestine.
- ItemPathogenicity of Beauveria bassiana PfBb and Immune Responses of a Non-Target Host, Spodoptera frugiperda (Lepidoptera: Noctuidae)(MDPI AG, 2022-10-08) Gao Y-P; Luo M; Wang X-Y; He X; Lu W; Zheng X-LExploring the pathogenicity of a new fungus strain to non-target host pests can provide essential information on a large scale for potential application in pest control. In this study, we tested the pathogenicity of Beauveria bassiana PfBb on the important agricultural pest Spodoptera frugiperda (Lepidoptera: Noctuidae) by determining the relative activities of protective enzymes and detoxifying enzymes in different larval instars. Our results show that the B. bassiana PfBb strain could infect all six larval instars of S. frugiperda, and its virulence to S. frugiperda larvae gradually increased with an increase in spore concentration. Seven days after inoculation, the LC50 of B. bassiana PfBb was 7.7 × 105, 5.5 × 106, 2.2 × 107, 3.1 × 108, 9.6 × 108, and 2.5 × 1011 spores/mL for first to sixth instars of S. frugiperda, respectively, and the LC50 and LC90 of B. bassiana PfBb for each S. frugiperda instar decreased with infection time, indicating a significant dose effect. Furthermore, the virulence of B. bassiana PfBb to S. frugiperda larvae gradually decreased with an increase in larval instar. The activities of protective enzymes (i.e., catalase, peroxidase, and superoxide dismutase) and detoxifying enzymes (i.e., glutathione S-transferases, carboxylesterase, and cytochrome P450) in S. frugiperda larvae of the first three instars infected with B. bassiana PfBb changed significantly with infection time, but such variations were not obvious in the fifth and sixth instars. Additionally, after being infected with B. bassiana PfBb, the activities of protective enzymes and detoxification enzymes in S. frugiperda larvae usually lasted from 12 to 48 h, which was significantly longer than the control. These results indicate that the pathogenicity of B. bassiana PfBb on the non-target host S. frugiperda was significant but depended on the instar stage. Therefore, the findings of this study suggest that B. bassiana PfBb can be used as a bio-insecticide to control young larvae of S. frugiperda in an integrated pest management program.
- ItemPrediction of seasonal population dynamics of Grapholita molesta (Busck) and Adoxophyes orana (Fischer von Röslerstamm) in peach orchards using sex pheromone trap and degree-days and its implications in pest management(2023-10-04) Ma A; Zhang H; Ran H; Yang X; J Hao J; Zhang J; Li H; Yu Z; Wang X; He X; Li JThe successful management of lepidopteran moths in orchards usually depends on the precise forecast of adult activity. However, the seasonal phenology of moths varies between crop cultivars and years, making it difficult to schedule the control measures. Here, we monitored male flight activity of oriental fruit moth Grapholita molesta and summer fruit tortrix moth Adoxophyes orana by using sex pheromone traps in peach orchards of three different cultivars for three successive years. We developed a logistic multiple-peaks model to fit data and then calculated degree-days (DD) required for male activity and neonate emergency. Results show that G. molesta and A. orana males had 4–5 and 3 flight peaks per year, respectively. The seasonal phenology of G. molesta or A. orana was quite stable with an identical timing of each flight peak between cultivars in a year. The flight activity was usually higher in the second and third peaks for both moths, with a higher cumulative number of G. molesta males captured than that of A. orana. Compared to A. orana, G. molesta emerged early in spring and required lower degree-days to reach the subsequent flight peaks and for neonate emergency. Our results suggest that to decline the possibility of outbreaks of moths during the growing seasons, pheromone traps should be scheduled in April with a cumulative DD between 49.6 and 207.1 for G. molesta and in mid-May–early June with a cumulative DD between 450.4 and 866.7 for A. orana, aiming to trap the newly emerged male adults or disrupting female mating success of overwintered moths in orchards. Based on the thermal requirement for egg hatching (i.e., 79.4 DD for G. molesta and 90.0 DD for A. orana), insecticide treatments would be applied in late-April–early May and late May–early June to reduce the field population density of neonates of G. molesta and A. orana, respectively, to reduce fruit damage in orchards. Furthermore, pheromone traps set up in late July–early August (573.8–1025.2 DD) for G. molesta and in mid-September (1539.7–1788.9 DD) for A. orana may suppress overwintering populations and thus decrease pest infestation in next year.
- ItemUAV Assisted Livestock Distribution Monitoring and Quantification: A Low-Cost and High-Precision Solution(MDPI AG, 2023-09-29) Ji W; Luo Y; Liao Y; Wu W; Wei X; Yang Y; Shen Y; Ma Q; He X; Yi S; Sun YGrazing management is one of the most widely practiced land uses globally. Quantifying the spatiotemporal distribution of livestock is critical for effective management of livestock-grassland grazing ecosystem. However, to date, there are few convincing solutions for livestock dynamic monitor and key parameters quantification under actual grazing situations. In this study, we proposed a pragmatic method for quantifying the grazing density (GD) and herding proximities (HP) based on unmanned aerial vehicles (UAVs). We further tested its feasibility at three typical household pastures on the Qinghai-Tibetan Plateau, China. We found that: (1) yak herds grazing followed a rotational grazing pattern spontaneously within the pastures, (2) Dispersion Index of yak herds varied as an M-shaped curve within one day, and it was the lowest in July and August, and (3) the average distance between the yak herd and the campsites in the cold season was significantly shorter than that in the warm season. In this study, we developed a method to characterize the dynamic GD and HP of yak herds precisely and effectively. This method is ideal for studying animal behavior and determining the correlation between the distribution of pastoral livestock and resource usability, delivering critical information for the development of grassland ecosystem and the implementation of sustainable grassland management.