Entomological Research最新文献

The fall armyworm, Spodoptera frugiperda (J. E. Smith), is a destructive pest of Zea mays (maize) and other agricultural crops. The synthetic insecticides predominantly used against this pest lead to pest resistance, environmental contamination and health hazards. This study evaluated nanoformulated aqueous extracts of some promising local plant species against third instar larvae of S. frugiperda under laboratory and field conditions. The initial screening bioassay showed highest larval mortality with a 20% extract of Nicotiana tabacum L. (66.67%), followed by Azadirachta indica A. Juss. (53.33%), Withania somnifera L. (46.67%), Melia azedarach L. (40%) and Dodonaea viscosa Jacq. (33.33%). The two most effective plant extracts (A. indica and N. tabacum) were further nanoformulated with silver nitrate (AgNO₃) and bioassayed against S. frugiperda larvae using different concentrations. The results showed that these nanoformulated extracts caused significant larval mortality, with LC₅₀ (lethal concentration that kills 50% of the population) and LT₅₀ (lethal time to kill 50% of the population) values of 37.36 and 28.21% at 72 h, and 52.19 and 33.25 h at 80% concentration, respectively. Field experiments on Zea mays L. (maize) plants showed maximum larval reduction by nanoformulated A. indica extract (48%), followed by N. tabacum extract (36%), whereas 80% and 20% larval reduction was noted for the positive (SuperLock®, emamectin benzoate and tebufenozide) and the negative (water) controls, respectively. Furthermore, characterization of both silver nanoparticles-based plant extract formulations was performed using ultraviolet–visible (UV–vis) spectroscopy, Raman spectroscopy and scanning electron microscopy (SEM) techniques, which confirmed the formation of silver nanoparticles. It is concluded that nanoformulated plant extracts can be an effective alternative to synthetic pesticides in combatting S. frugiperda and other lepidopteran pests.

Euphorbia L. includes 2055 species with native range of this genus being cosmopolitan. In the present study, we assessed pollen morphology of 18 species of this genus occurring mostly in northern Pakistan. Pollen morphology of Euphorbia species is poorly investigated for its taxonomic significance. Here, we examined quantitative characters, including polar diameter, equatorial diameter, P/E ratio. Exine thickness, colpi length, and width were also examined. Among the qualitative characters, pollen shape, type, exine sculpturing, and aperture features were determined. The main aim of this study is to determine and investigate the foraging behavior of the honeybees that interact with Euphorbia species. The current finding will be helpful in melissopalynological analysis for developing beekeeping practices and can be used in the authentication of honey. Pollen quantitative traits applied through a multivariate analysis and diverse sampling also improve botanical and geographical characterization of a particular region. In addition, it is concluded that some palynomorphs of Euphorbia species may contain secondary compounds and can promote signs of toxicity in honeybees. However, the beekeepers wrongly correlate the fact that milky latex from Euphorbia taxa has burning and skin irritation effects on other animals, particularly humans, with honeybee deaths, which might be due to other factors. Our observations indicate with the sense that actual forage plants may not poison their pollinators and honeybees might occasionally be dead due to unidentified factors. We have suggested that beekeepers should attempt to identify the root causes for occasional bee deaths in the area.

The green peach aphid Myzus persicae Sülzer is a major insect pest of cruciferous plants, including vegetables such as Chinese cabbage. The objective of the present study was to determine the effects of sublethal afidopyropen and spirotetramat concentrations on the survival and reproduction of M. persicae. In addition, we used an electrical penetration graph (EPG) to study the feeding behavior of M. persicae on Chinese cabbage leaves treated with various concentrations of afidopyropen, spirotetramat and sulfoxaflor. The results showed that sublethal concentrations (LC₁₀ and LC₃₀) of afidopyropen and spirotetramat significantly decreased adult longevity and fecundity. However, sulfoxaflor had no significant effects. Several population parameters, including the net reproductive rate (R₀), intrinsic rate of increase (r_m), mean generation time (T), finite rate of increase (λ), and doubling time (DT), were significantly decreased only at the LC₃₀ of spirotetramat. According to the EPG feeding behavior analyses, when all three insecticides were applied at LC₃₀, the nonpenetration (NP) waveform significantly increased. The above results can be used as basic data for the well-planned use of insecticides.

Many types of livestock waste can be treated with insect larvae; however, in-depth research on the decomposition ability of Protaetia brevitarsis seulensis (PBS) larvae and the characteristics of manure after treatment with PBS is extremely limited. Therefore, this study examined the decomposition ability and survival rates of different instars of PBS larvae and their effects on the characteristics and pathogen counts of pig manure. Two treatments were designed: 1 kg of second instar or third instar PBS larvae per 10 kg of pig manure. Pig manure did not affect the decomposing capacity and survival rates of the two PBS larval instar groups (P > 0.05). However, the decomposition abilities of the different PBS larval instar groups on days 2, 7 and 8 significantly differed (P < 0.05). Over time, the changes observed in pH, moisture, total nitrogen, acid detergent fiber (ADF), neutral detergent fiber (NDF) and hemicelluloses did not significantly differ (P > 0.05) between treatments using second or third instar PBS larvae. On day 15, both total nitrogen and NDF significantly differed (P < 0.05) between the two treatment groups. During the experimental period, no significant (P > 0.05) change in Escherichia coli or Salmonella counts was observed in pig manure treated with different PBS larval instars. Our findings suggest that the decomposition abilities and survival rates of larvae and pig manure characteristics and pathogen counts do not differ for different PBS larval instar stages.

In this study, the morphology and distribution of antennal sensilla of male and female adults of Plautia stali were investigated using scanning electron microscopy. In both sexes, the antennae of P. stali were composed of a scape, two-segmented pedicels (P1 and P2) and two-segmented flagellomeres (F1 and F2). There were no differences in the overall length and shape between males and females. Four basic types of sensilla (s. trichodea, s. basiconica, s. chaetica and s. coeloconica) were identified in each sex. Sensilla basiconica and s. chaetica were further divided into four and two subtypes, respectively. Among the sensilla, s. trichodea and s. basiconica subtype 4 were multiporous, indicating that these two types are involved in olfactory functions. There was an apical pore on the tip of s. basiconica subtypes 2 and 3, suggesting that they have contact chemosensory function. There was no pore on the cuticular surface of the other types of sensilla, suggesting that these types may be mechano-, thermo- or hygroreceptors. Sexual dimorphism was not evident in the distribution of the four types of sensilla, although there were variations in the number and distribution of sensilla along with the antennae in both sexes. This study reveals information regarding the sensory function of each type of sensillum in P. stali.

To determine the control mechanism of garlic on Myzus persicae, volatiles from garlic plants were collected, and the components were determined by GC–MS. Then, the volatile extracts and standard components were screened by electroantennogram (EAG) apparatus and Y-tube olfactometer, and the toxic effects were determined by the immersion method. The results showed the main components from garlic plant volatile were 2-methoxyphenol, 2,4-di-tert-butylphenol, diallyl disulfide, butyl phthalate esters, (1-hydroxycyclohexyl) phenyl ketone, and 2,6-di-tert-butylp-cresol. The volatile extracts and the standard components had significant repellent effects (P ≤ 0.05) on M. persicae when the volume ratio was 1:100. The relative values of EAG from volatile extracts and diallyl disulfide were significantly higher than those of the other substances (P ≤ 0.05) when the volume ratio was 1:100. The toxicity of garlic volatile extracts to M. persicae significantly (P ≤ 0.05) increased with increasing concentration. After 72 h (treated), the adjusted mortality of the extract to M. persicae was 36.99% at 90 ml/L. The standard components had the significant toxic effect on M. persicae at 30 mg/mL, and the rates of mortality were over 78.95%. Thus, the results suggested that the volatile extracts and the four standard components from garlic plants had significant repellent effects and electroantennogram responses for M. persicae, and the toxic effects were stronger than the repellent effects for M. persicae.

Bacteria-originated volatile molecules play a crucial role in chemical communications between insects, representing their promising application as odor bait traps in pest control. In this study, we investigated the behavioral preferences of the fruit fly Drosophila melanogaster (Diptera: Drosophilidae) towards the fermentation broth of seven gut-associated bacteria using trap choice assays. All seven bacterial fermentations significantly attracted adults and larvae compared to the medium control. We assessed the effects of bacterial fermentations on bayberry attractiveness to fly adults, and found that the bayberries sprayed with fermentation broth of seven bacteria were all significantly more attractive to adults than the non-sprayed, following in increased total egg numbers. We also compared the attractive effect of bacterial fermentations with a sugar-vinegar mixture and a commercial odor-bait. The commercial odor bait proved more enticing than the unconcentrated 5-day fermentation broths. However, out of the seven bacteria, 64-fold concentrated bacterial fermentation of Corynebacterium (Actinomycetota phylum) was significantly more attractive than commercial bait. Finally, we chemically identified the predominant compounds 2-methylpropanal and acetaldehyde, which are likely responsible for the behavioral preference of fruit flies. Our findings provide a deeper understanding of how gut microbes affect insect behavior and offer a potential bacteria-originated odor bait for fly control in the orchard.

This study investigates the mosquitocidal potential of crude petroleum ether extract fractions derived from Gloriosa superba against the dengue mosquito vector Aedes aegypti. Chemical profiling through gas chromatography identified four major metabolites, with nonadecane showing the highest peak area percentage (70.34%). A lethal dosage of fraction IV of G. superba (Gs-F4), at a maximum concentration of 5.0 ppm, exhibited high mortality rates in second (78%), third (71%) and fourth (51%) instars of Ae. aegypti. A sublethal dosage of Gs-F4 (3.0 ppm) significantly altered the larval midgut enzymes of cytochrome P450, esterases and glutathione S-transferases. The repellent activity of Gs-F4 was dosage dependent, with repellency percentages decreasing from 96% to 50% as the exposure time increased from 15 to 210 mins. The impact of Gs-F4 on aquatic mosquito predators was marginally toxic (<50%) compared with the commercial compound temephos (1.0 ppm), which exhibited a higher toxicity (>50%). In silico toxicity screening using the BeeToxAI server indicated that three of the four compounds in Gs-F4 were safe or non-toxic to honeybees, except for α-gurjunene (6.29 μg/bee). Although G. superba demonstrates effective larvicidal and repellent activity against Ae. aegypti, the non-target toxicity against mosquito predators necessitates further toxicological screening on beneficial species under field conditions.

Fas-associated death domain protein (FADD) is an apoptotic adapter molecule that recruits caspases and facilitates the formation of death-inducing signaling complexes in mammals. In lower animals, FADD forms a complex with immune deficiency and death-related ced-3/Nedd2-like caspase to elicit antimicrobial responses. In this study, we characterized the FADD sequence of Tenebrio molitor (TmFADD) using molecular informatics to understand its role in immune surveillance of the host against microorganisms. The 618 bp open reading frame of TmFADD encodes a polypeptide of 204 amino acids. The protein includes two promiscuous domains, the death-effector domain and the death domain, found at the N- and C-termini, respectively. TmFADD is clustered with the coleopteran FADD sequences in the phylogenetic tree. Homology-based structural analysis showed an α-helical model with a QMEAN score of 0.58. The expression of TmFADD mRNA was conspicuous in the larval and early pupal stages. TmFADD mRNA was distributed in the immune tissues of the larva and was found predominately in the gut of the adult. Infection of the host with Candida albicans, Escherichia coli or Staphylococcus aureus increased the expression of TmFADD mRNA, suggesting that these microorganisms trigger the innate immunity of the host. The silencing of TmFADD transcripts resulted in an increased susceptibility of T. molitor larvae to infection with E. coli, but not to infection with C. albicans or S. aureus. Hence, these results indicate that FADD plays a role in the defense of T. molitor and could open avenues for understanding insect immunity.

This research delves into the effects of weir-induced habitat fragmentation on the diversity and structure of benthic macroinvertebrate communities in Topyeong Stream in the Republic of Korea. Through comprehensive zonation, environmental assessments and analyses of macroinvertebrate populations, the study brings to light the significant impact of physical barriers within aquatic ecosystems. Findings reveal notable differences in macroinvertebrate diversity among various stream zones, with alpha diversity measurements demonstrating the significant influence of habitat conditions on biodiversity. Beta diversity analyses uncovered considerable species turnover, pointing to distinct ecological features within fragmented habitats. Mantel tests solidified a significant link between geographical separation and species composition, highlighting the critical impact of spatial isolation arising from habitat fragmentation. The research also pinpointed environmental factors, including habitat size and depth variation, as critical influences on macroinvertebrate community dynamics. Discussions on conservation tactics centered on habitat restoration and forward-thinking water management strategies aim to counteract the negative consequences of fragmentation and drought. This study emphasizes the essential need for cohesive conservation initiatives to preserve aquatic biodiversity and the functionality of ecosystems amidst human-induced challenges.