Genetic and morphometric differentiation between two morphs of Haematobosca sanguinolenta (Diptera: Muscidae) from Thailand.

Haematobosca is a genus of biting fly within the subfamily Stomoxyinae of the family Muscidae. It is currently recognized to include 16 species worldwide. These species, acting as ectoparasites, are considered to have significant importance in the veterinary and medical fields. To address the color polymorphism related to the genus Haematobosca in Thailand, herein, we focused on the normal (legs mainly black) and yellow (legs mainly yellow) morphs of Haematobosca sanguinolenta and examined them for genetic differences using three molecular markers: the cytochrome c oxidase subunit 1 (cox1) and cytochrome b (cytb) genes from the mitochondrial genome as well as the internal transcribed spacer 2 (ITS2) region from the nuclear ribosomal DNA. In addition, we analyzed wing differences between the two morphs using geometric morphometrics (GM). The genetic divergences between the two morphs showed that cytb gene showed the greatest divergence, for which the average distance was 5.6%. This was followed by the combination of cox1-cytb-ITS2, exhibiting an average divergence of 4.5%, ITS2 with a divergence of 4.1%, and finally cox1, showing the lowest divergence of 3.5%. Phylogenetic analyses distinctly separated the two morphs of H. sanguinolenta; this separation was supported by high bootstrap values (97-100%). These results were further corroborated by three species delimitation methods, i.e. assemble species by automatic partitioning (ASAP), automated barcode gap discovery (ABGD), and Poisson tree processes (PTP), all of which suggested that the two morphs likely represent separate species. In addition, a GM study identified a statistically significant difference in wing shape between the two morphs of H. sanguinolenta (P < 0.05). This combination of genetic and morphometric results strongly supports the existence of two distinct species within H. sanguinolenta in Thailand.

Demographic inference from the mt-DNA COI gene and wing geometry of Culex gelidus (Diptera: Culicidae), an important vector of Japanese encephalitis in Thailand.

Culex gelidus (Diptera: Culicidae), an important vector of the Japanese encephalitis virus (JEV), contributes to human viral encephalitis in many Asian countries, including Thailand. This study represents the first investigation of the demographic patterns of Cx. gelidus populations in Thailand using cytochrome c oxidase subunit I (COI) gene analysis and wing geometric morphometrics (GM). Mosquitoes were collected from 10 provinces across six regions of Thailand in 2022. Analysis of the COI sequences (n = 182) indicated high haplotype diversity (0.882) and low nucleotide diversity (0.006), with 72 haplotypes identified. The haplotype network demonstrated no profound splits among the geographic populations. Neutral tests, including Tajima's D and Fu's Fs, displayed negative values, with a significant result observed for Fu's Fs (-33.048, p < 0.05). The mismatch distribution analysis indicated that the population does not statistically deviate from a model of sudden population expansion (SSD = 0.010, p > 0.05; Rg = 0.022, p > 0.05). The estimations suggest that the Cx. gelidus population in Thailand began its expansion approximately between 459,243 and 707,011 years ago. The Mantel test showed no significant relationship between genetic and geographic distances (r = 0.048, p > 0.05). Significant phenotypic differences (based on wing shape) were observed among most populations. Additionally, in this study, we found no significant relationships between phenotypic and genetic distances (r = 0.250, p > 0.05). Understanding the genetic and morphological dynamics of Cx. gelidus is vital for developing targeted surveillance and vector control measures. This knowledge will also help to predict how future environmental changes might affect these populations, thereby informing long-term vector management strategies.

Geometric morphometrics to differentiate species and explore seasonal variation in three Mansonia species (Diptera: Culicidae) in central Thailand and their association with meteorological factors.

Mansonia mosquito species are recognised as a significant vector of human pathogens, primarily transmitting the filarial nematode, Brugia malayi. In central Thailand, the three most prevalent Mansonia species are Mansonia annulifera, Mansonia indiana and Mansonia uniformis. This study explored the influence of seasonal changes on the phenotypic variation of these Mansonia species in central Thailand using the geometric morphometrics (GM). To ensure accurate species identification, we integrated GM techniques with DNA barcoding, examining distinctions in both phenotype and genotype among the species. The intraspecific genetic divergence ranged from 0.00% to 1.69%, whereas the interspecific genetic divergence ranged from 10.52% to 16.36%. The clear distinction between intra- and interspecific distances demonstrated the presence of a barcoding gap, confirming the successful differentiation of the three Mansonia mosquito species through DNA barcoding. Similarly, the interspecies GM assessment for classifying Mansonia species demonstrated a high degree of accuracy, with an overall performance of 98.12%. Exploring seasonal variation in the three Mansonia species revealed wing variations across different seasons, and pronounced variations appearing in the cool season. Regarding their association with meteorological factors, Ma. annulifera and Ma. uniformis showed significant positive correlations with temperature (p < 0.05), and Ma. uniformis also displayed a significant negative correlation with atmospheric pressure (p < 0.05). The insights from this study will deepen our understanding of the adaptive patterns of Mansonia mosquitoes in Thailand's central region, paving the way for enhanced disease surveillance related to these vectors.

Population genetic structure and wing geometric morphometrics of the filarial vector Armigeres subalbatus (Diptera: Culicidae) in Thailand.

Armigeres subalbatus (Diptera: Culicidae) is a mosquito species of significant medical and veterinary importance. It is widely distributed across Southeast and East Asia and is commonly found throughout Thailand. This study assessed the genetic diversity and population structure of Ar. subalbatus in Thailand using the cytochrome c oxidase subunit I (COI) gene sequences. Additionally, wing shape variations among these populations were examined using geometric morphometrics (GM). Our results demonstrated that the overall haplotype diversity (Hd) was 0.634, and the nucleotide diversity (π) was 0.0019. Significant negative values in neutrality tests (p < 0.05) indicate that the Ar. subalbatus populations in Thailand are undergoing a phase of expansion following a bottleneck event. The mismatch distribution test suggests that the populations may have started expanding approximately 16,678 years ago. Pairwise genetic differentiation among the 12 populations based on Fst revealed significant differences in 32 pairs (p < 0.05), with the degree of differentiation ranging from 0.000 to 0.419. The GM analysis of wing shape also indicated significant differences in nearly all pairs (p < 0.05), except for between populations from Nakhon Pathom and Samut Songkhram, and between those from Chiang Mai and Mae Hong Son, suggesting no significant difference due to their similar environmental settings. These findings enhance our understanding of the population structure and phenotypic adaptations of mosquito vectors, providing vital insights for the formulation of more efficacious vector control strategies.

Insights into the mitochondrial cytochrome oxidase I (mt-COI) gene and wing morphometrics of Anopheles baimaii (Diptera: Culicidae) in malaria-endemic islands of Thailand.

Anopheles baimaii (Diptera: Culicidae) significantly contributes to the transmission of parasites causing malaria in Southeast Asia and South Asia. This study examined the morphological (wing shape) and molecular (mitochondrial gene) variations of An. baimaii in four of Thailand's border islands, and also investigated the presence of Plasmodium parasites in these mosquitoes. No Plasmodium infections were detected in the samples. Significant differences in wing shape were observed in most island populations (p < 0.05). A single-linkage tree, constructed using Mahalanobis distances, clustered the populations into two groups based on geographical locations. Genetic variation in An. baimaii was also analyzed through cytochrome c oxidase subunit I (COI) gene sequences. This analysis identified 22 segregating sites and a low nucleotide diversity of 0.004. Furthermore, 18 distinct haplotypes were identified, indicating a high haplotype diversity of 0.825. Neutrality tests for the overall population revealed a significantly negative Fu's Fs value (-5.029), indicating a population expansion. In contrast, Tajima's D yielded a negative value (-1.028) that did not reach statistical significance. The mismatch distribution analysis exhibited a bimodal pattern, and the raggedness index was 0.068, showing no significant discrepancy (p = 0.485) between observed and expected distributions. Pairwise genetic differentiation assessments demonstrated significant differences between all populations (p < 0.05). These findings provide valuable insights into the COI gene and wing morphometric variations in An. baimaii across Thailand's islands, offering critical information for understanding the adaptations of this malaria vector and guiding future comprehensive research.

Wing geometric morphometrics and DNA barcoding to distinguish three closely related species of Armigeres mosquitoes (Diptera: Culicidae) in Thailand.

Armigeres subalbatus, a mosquito species widely found in Thailand and other Asian countries, serves as a vector for filarial parasites, affecting both humans and animals. However, the surveillance of this vector is complicated because of its morphological similarity to two other species, Armigeres dohami and Armigeres kesseli. To differentiate these morphologically similar species, our study employed both wing geometric morphometrics (GM) and DNA barcoding, offering a comprehensive approach to accurately identify these closely related Armigeres species in Thailand. Our GM analyses based on shape demonstrated significant accuracy in differentiating Armigeres species. Specifically, the outline-based GM method focusing on the 3rd posterior cell exhibited an accuracy rate of 82.61%, closely followed by the landmark-based GM method with 81.54%. Both these GM techniques effectively distinguished Ar. subalbatus from Ar. dohami and Ar. kesseli. Regarding DNA barcoding, our investigation of pairwise intra- and interspecific divergences revealed a "barcoding gap". Furthermore, the results of species confirmation using both species delimitation methods including the automatic barcode gap discovery method (ABGD) and the Multi-rate Poisson tree process (mPTP) were consistent with those of morphological identification, sequence comparisons with the GenBank and Barcode of Life Data System (BOLD) databases, and the neighbor-joining tree construction. These consistent results emphasize the efficacy of DNA barcoding in the precise identification of Armigeres species.

Outline-based geometric morphometrics: Wing cell differences for mosquito vector classification in the Tanaosri mountain range, Thailand.

Recent studies have revealed taxonomic signals within the wing cells of certain mosquito species. In our study, wing cell differentiation among mosquito vectors from the Tanaosri mountain range in Thailand was evaluated using the outline-based geometric morphometric (GM) approach. Our focus was on four specific wing cells for GM analysis: the wing contour (external cell), the second submarginal cell (internal cell 1), the first posterior cell (internal cell 2), and the third posterior cell (internal cell 3). Before proceeding with the GM approach, the identity of seven mosquito genera and 21 species was confirmed using molecular techniques. Our validated classification tests demonstrated that the performance of mosquito species classification varies according to genus. Notably, three Aedes species exhibited the highest accuracy for both internal cell 2 and internal cell 3, each registering a score of 93.20 %. In the case of two Mansonia species, the wing contour displayed a remarkable accuracy of 98.57 %. Consequently, we suggest the use of the outline-based GM approach, particularly focusing on the wing contour, for differentiating Mansonia annulifera and Mansonia uniformis. In contrast, the highest accuracy for classifying Culex species was found in internal cell 1, at 75.51 %, highlighting the challenges due to similarities in wing cells within this genus. These findings provide a guideline for future applications of the outline-based GM approach, focusing on wing cells, as an alternative method to classify mosquito vector species.

Molecular characterization and genetic diversity of three Stomoxys flies S. bengalensis, S. calcitrans, and S. sitiens (Diptera: Muscidae) in Central Thailand.

Stomoxys flies (Diptera: Muscidae) are hematophagous ectoparasites of medical and veterinary importance. In this study, three Stomoxys species, i.e. S. bengalensis, S. calcitrans, and S. sitiens, were collected from three provinces in Central Thailand with the aim of estimating the genetic divergence between species, for species identification, as well as within species, for a genetic diversity study based on the cytochrome c oxidase subunit I (COI) gene. Our results showed that the average intraspecific genetic divergences of Stomoxys flies ranged from 0.11% in S. sitiens to 0.98% in S. calcitrans, whereas the average interspecific genetic divergences ranged from 5.24% between S. sitiens and S. bengalensis to 6.69% between S. calcitrans and S. bengalensis. In addition, there was no overlap between the intraspecific and interspecific genetic divergences. The COI sequence analysis revealed a high haplotype diversity and low nucleotide diversity, reflecting a rapid population expansion after past bottlenecks. Moreover, there was no significant difference (P > 0.05) in the pairwise population differentiation (Fst) among Stomoxys flies in Central Thailand, because of the lack of natural barriers, thus allowing genetic exchange between them. The monitoring of the haplotype network revealed that two lineages of S. calcitrans in Central Thailand were distributed in all study areas, including the Nakhon Pathom, Pathum Thani, and Saraburi Provinces. These findings may improve our understanding of the genetic patterns of these three Stomoxys flies, as well as the underlying biological mechanisms, which is knowledge that can be used for further effective control of these flies.

Spent Coffee Grounds and Novaluron Are Toxic to Aedes aegypti (Diptera: Culicidae) Larvae.

Aedes aegypti (Diptera: Culicidae) is a vector for mosquito-borne diseases worldwide. Insecticide resistance is a major concern in controlling this mosquito. We investigated the chemical compounds in wet and dry spent coffee grounds (wSCGs and dSCGs) and evaluated the efficacy of dSCGs, wSCGs, and novaluron on the mortality and adult emergence inhibition of Ae. aegypti. We found higher concentrations of chemical compounds in wSCGs than in dSCGs. The wSCGs and dSCGs both contained total phenolic compounds, total flavonoid compounds, caffeic acid, coumaric acid, protocatechuic acid, and vanillic acid. Complete mortality was observed after 48 h of exposure to 50 g/L wSCGs, while similar mortality was found after 120 h of exposure to 10 µg/L of novaluron. The sublethal dose was a concentration of wSCGs (5 g/L) and novaluron (0.01, 0.1, and 1 µg/L) combined that resulted in a larval mortality lower than twenty percent (at 72 h) to determine their synergistic effects. The death rate of larvae exposed in sublethal combination of wSCGs and novaluron was significantly higher than that of its stand-alone. The findings indicate that the combination of wSCGs and novaluron at sublethal concentrations had synergistic effects on the mortality of Ae. aegypti larvae and could be applied as an alternative control measure.

Molecular and morphometric differentiation of secondary filariasis vector Coquillettidia mosquitoes (Diptera: Culicidae) in Thailand.

Coquillettidia mosquitoes are important nuisance-biting pests and a vector of brugian filariasis in Thailand. However, comprehensive information about these mosquitoes remains unavailable such as molecular and morphometric differences among species. The lack of vector knowledge on Coquillettidia species could affect future disease control. This study aims to investigate differences in molecular variations based on mitochondrial cytochrome oxidase subunit I (COI) gene and wing geometric traits of three Coquillettidia species, namely Cq. crassipes, Cq. nigrosignata, and Cq. ochracea in Thailand. The results of molecular analyses revealed the differences among three Coquillettidia species. The genetic difference measure based on the Kimura two-parameter model among three Coquillettidia species showed low intraspecific distances (0%-3.05%) and large interspecific distances (10.10%-12.41%). The values of intra- and inter-genetic differences of three Coquillettidia species did not overlap which showed the existence of a barcoding gap indicating the efficiency of the identification based on the COI gene. As with molecular analysis, the landmark-based geometric morphometrics approach based on wing shape analysis indicated three distinct species groups which were supported by the high total performance score of cross-validated classification (97.16%). These results provide the first evidence of taxonomic signal based on molecular and wing geometric differences to support species identification and biological variations of Coquillettidia mosquitoes in Thailand for understanding these rare vector mosquitoes in depth and leading to effective further mosquito control.

Wing geometric morphometrics to distinguish and identify Haematobosca flies (Diptera: Muscidae) from Thailand.

The hematophagous flies of the genus Haematobosca Bezzi, 1907 (Diptera: Muscidae) are important ectoparasites in domestic animals and wildlife. Two species of this genus have been recorded in Thailand, viz., Haematobosca sanguinolenta (Austen, 1909) and Haematobosca aberrans (Pont, Duvallet & Changbunjong, 2020). They have a similar morphology and coexist in the same habitat. The correct species identification of these flies is extremely important for understanding disease epidemiology and developing effective control measures. Geometric morphometrics (GM) has been confirmed to be a useful tool for differentiating and identifying morphologically similar insect species. Therefore, GM was used to distinguish and identify H. sanguinolenta and H. aberrans in Thailand. Adult flies of both sexes were collected using Nzi traps, morphologically identified, and analyzed by landmark-based GM of the wing. Results showed that GM was highly effective in distinguishing the two Haematobosca species based on their wing shape, with an overall accuracy score of 99.3%. We also revealed that our study material could be used as reference data to identify new field specimens collected from other geographic locations. We propose that wing GM can be used as a supplement to conventional morphology identification, particularly for Haematobosca specimen that has been damaged or has lost its diagnostic characteristics due to specimen collection and processing in the field.

Effects of Piper nigrum L. Fruit Essential Oil Toxicity against Stable Fly (Diptera: Muscidae).

The efficacy of Piper nigrum L. fruit essential oil (EO) against Stomoxys calcitrans (stable fly), a blood-feeding fly distributed worldwide, was investigated. This study aimed to evaluate the insecticidal activity of EO based on contact and fumigant toxicity tests. Chemical analysis of the EO using gas chromatography-mass spectrometry revealed that sabinene (24.41%), limonene (23.80%), ß-caryophyllene (18.52%), and α-pinene (10.59%) were the major components. The results demonstrated that fly mortality increased with increasing EO concentration and time during the first 24 h of exposure. The median lethal dose was 78.37 µg/fly for contact toxicity, while the 90% lethal dose was 556.28 µg/fly. The median lethal concentration during fumigant toxicity testing was 13.72 mg/L air, and the 90% lethal concentration was 45.63 mg/L air. Our findings suggested that essential oil extracted from P. nigrum fruit could be a potential natural insecticidal agent for control of stable fly. To examine the insecticidal properties of P. nigrum fruit EO, further field trials and investigation into the efficacy of nano-formulations are required.

Species Discrimination of Stomoxys Flies S. bengalensis, S. calcitrans, and S. sitiens (Diptera: Muscidae) Using Wing Geometric Morphometrics.

The flies of the genus Stomoxys Geoffroy, 1762 (Diptera: Muscidae), are regarded as pests of veterinary and medical importance. In Thailand, Stomoxys calcitrans (Linnaeus, 1758) is the most abundant species and is widely distributed throughout the country. This Stomoxys species can coexist with two other morphologically similar species: Stomoxys bengalensis Picard, 1908, and Stomoxys sitiens Rondani, 1873. Hence, discriminating using morphological characteristics is difficult, especially if the specimen is damaged or loses its diagnostic characteristics. In this study, we evaluated the effectiveness of the landmark-based geometric morphometric (GM) approach to discriminate among the three Stomoxys spp.: S. bengalensis, S. calcitrans, and S. sitiens. Left-wing images of S. bengalensis (n = 120), S. calcitrans (n = 150), and S. sitiens (n = 155) were used for the GM analyses. The results of the wing shape analyses revealed that the GM approach was highly effective for discriminating three Stomoxys, with high accuracy scores ranging from 93.75% to 100%. This study adds to the evidence that landmark-based GM is an excellent alternative approach for discriminating Stomoxys species.

Evaluation of Modern Techniques for Species Identification of Lutzia Mosquitoes (Diptera: Culicidae) in Thailand: Geometric Morphometrics and DNA Barcoding.

There are four species of Lutzia mosquitoes in Thailand, including Lutzia chiangmaiensis, Lt. fuscana, Lt. halifaxii, and Lt. vorax. The accurate species identification of adult Lutzia mosquitoes based on morphological features requires many body parts, including the abdominal terga and wing. However, species identification is difficult in the case of damaged specimens when some of their morphological character is missing due to transit or gathering in the field. Thus, we evaluated the efficacy of the landmark-based geometric morphometric (GM) approach for the discrimination of Lutzia species in Thailand. In addition, DNA barcoding was also used in parallel with the GM approach to identify the species. Larvae of Lutzia were collected, raised into adults, and identified based on their morphological characteristics. The validated reclassification test results clearly demonstrated that wing shape resulted in a high level of success in identification (correct identifications ranged from 92.50% to 100%); however, based on the DNA barcoding analyses, our results showed that it was poorly effective in identifying Lt. fuscana and Lt. halifaxii based on an overlap between the intraspecific and interspecific divergence. Moreover, our survey results provide updates on the distribution of Lt. chiangmaiensis and Lt. vorax in Thailand. This research will help medical entomologists more efficiently identify mosquitoes in the genus Lutzia, resulting in more effective mosquito control and surveillance.

Effects of Coleus amboinicus L. Essential Oil and Ethanolic Extracts on Planktonic Cells and Biofilm Formation of Microsporum canis Isolated from Feline Dermatophytosis.

Microsporum canis is an important zoonotic fungus that causes dermatophytosis in domestic animals and their owners. Domestic cats are the primary reservoir for M. canis. Antifungal drugs frequently produce adverse effects on the host animal, increasing the demand for novel alternative treatments derived from nature. We evaluated the antifungal activity of Coleus amboinicus essential oil (CEO) and ethanolic extracts (CEE) against M. canis in planktonic and biofilm growth. Twelve clinical isolates of M. canis were identified in feline dermatophyte samples. Using GC-MS, 18 compounds were identified in CEO, with carvacrol being the major constituent. HPLC analysis of CEE revealed that it contained rosmarinic acid, apigenin, and caffeic acid. The planktonic growth of all M. canis isolates was inhibited by C. amboinicus extracts. The minimum inhibitory concentration at which ≥50% of the isolates were inhibited (MIC50) was 128 µg/mL (32-256 µg/mL) for both CEO and CEE. The MIC90 values of CEO and CEE were 128 and 256 µg/mL, respectively. CEO at MIC (128 µg/mL) and 2× MIC (256 µg/mL) significantly inhibited the biofilm formation of weak, moderate, and strong biofilm-producing M. canis. CEE at 2× MIC (256 µg/mL) significantly inhibited the biofilm formation of all isolates. Overall, C. amboinicus extracts inhibited planktonic growth and exhibited a significant antibiofilm effect against M. canis. Thus, C. amboinicus is a potential source of natural antifungal compounds.

Genetic Diversity, Haplotype Relationships, and kdr Mutation of Malaria Anopheles Vectors in the Most Plasmodium knowlesi-Endemic Area of Thailand.

Plasmodium knowlesi, a malaria parasite that occurs naturally in long-tailed macaques, pig-tailed macaques, and banded leaf monkeys, is currently regarded as the fifth of the human malaria parasites. We aimed to investigate genetic diversity based on the cytochrome c oxidase subunit I (COI) gene, detect Plasmodium parasites, and screen for the voltage-gated sodium channel (VGSC)-mutation-mediated knockdown resistance (kdr) of Anopheles mosquitoes in Ranong province, which is the most P. knowlesi-endemic area in Thailand. One hundred and fourteen Anopheles females belonging to eight species, including An. baimaii (21.05%), An. minimus s.s. (20.17%), An. epiroticus (19.30%), An. jamesii (19.30%), An. maculatus s.s. (13.16%), An. barbirostris A3 (5.26%), An. sawadwongporni (0.88%), and An. aconitus (0.88%), were caught in three geographical regions of Ranong province. None of the Anopheles mosquitoes sampled in this study were infected with Plasmodium parasites. Based on the sequence analysis of COI sequences, An. epiroticus had the highest level of nucleotide diversity (0.012), followed by An. minimus (0.011). In contrast, An. maculatus (0.002) had the lowest level of nucleotide diversity. The Fu's Fs and Tajima's D values of the Anopheles species in Ranong were all negative, except the Tajima's D values of An. minimus (0.077). Screening of VGSC sequences showed no presence of the kdr mutation of Anopheles mosquitoes. Our results could be used to further select effective techniques for controlling Anopheles populations in Thailand's most P. knowlesi-endemic area.

Geometric morphometric and molecular techniques for discriminating among three cryptic species of the Anopheles barbirostris complex (diptera: culicidae) in Thailand.

Anopheles members of the Barbirostris complex are important vectors of malaria in Thailand. However, they are morphologically indistinguishable because they are closely related species. In this study, wing geometric morphometrics (GM) and DNA barcoding based on the cytochrome c oxidase subunit 1 (C O I) gene were applied to differentiate cryptic species of the Barbirostris complex in Thailand. Three cryptic species of the Barbirostris complex, Anopheles dissidens (19.44%), Anopheles saeungae (24.54%), and Anopheles wejchoochotei (56.02%) were initially identified using the multiplex polymerase chain reaction assay. DNA barcoding analyses showed low intraspecific distances (range, 0.27%-0.63%) and high interspecific distances (range, 1.92%-3.68%), consistent with the phylogenetic analyses that showed clear species groups. While wing size and shape analyses based on landmark-based GM indicated differences between three species (p < 0.05). The cross-validated reclassification revealed that the overall efficacy of wing size analysis for species identification of the Barbirostris complex was less than the wing shape analysis (56.43% vs. 74.29% total performance). Therefore, this study's results are guidelines for applying modern techniques to identify members within the Barbirostris complex, which are still difficult to distinguish by morphology-based identification and contribute to further appropriate malaria control.

Physicochemical Properties of Sugarcane Cultivars Affected Life History and Population Growth Parameters of Sesamia nonagrioides (Lefebvre) (Lepidoptera: Noctuidae).

The use of resistant cultivars is an efficient management strategy against S. nonagrioides. The effects of different sugarcane cultivars, CP48-103, CP57-614, CP69-1062, CP73-21, SP70-1143, and IRC99-02 were evaluated on the oviposition preference (free-choice assay), life history, and life table parameters of S. nonagrioides at 27 ± 1 °C, 60 ± 5% RH and a photoperiod of 16: 8 (L: D) h. The longest and shortest developmental times were on cultivars SP70-1143 and CP48-103, respectively. The oviposition preference of S. nonagrioides was the highest on cultivars CP48-103 and CP69-1062, and negatively correlated with the shoot trichome density and shoot rind hardness of the cultivars. The highest intrinsic rate of increase of S. nonagrioides was on cultivar CP48-103 and the lowest was on cultivar SP70-1143. The shortest mean generation time was on CP48-103 and the longest was on SP70-1143. The results indicate that cultivars CP48-103 and CP69-1062 were susceptible, and cultivar SP70-1143 was partially resistant against S. nonagrioides. This information could be useful for developing integrated management programs of S. nonagrioides, such as the use of resistant cultivars to reduce the damage caused by this pest in sugarcane fields.

Nanoencapsulation of Acetamiprid by Sodium Alginate and Polyethylene Glycol Enhanced Its Insecticidal Efficiency.

Nanoformulation has been considered one of the newly applied methods in integrated pest management strategies. In this research, a conventional neonicotinoid insecticide acetamiprid was nanoencapsulated via AL (Sodium Alginate) and PEG (Polyethylene Glycol) and tested against the elm leaf beetle Xanthogaleruca luteola. The synthesized particles had spherical-like morphology and nanoscale based on TEM (Transmission Electron Microscopy) and DLS (Dynamic Light Scattering). The encapsulation efficiency and loading percentages of acetamiprid in AL and PEG were 92.58% and 90.15%, and 88.46% and 86.79%, respectively. Leaf discs treated with different formulations by the leaf-dipping method were used for oral toxicity assays. The LC50 values (Lethal Concentration to kill 50% of insect population) of acetamiprid and Al- and PEG-nanoencapsulated formulations on third-instar larvae were 0.68, 0.04, and 0.08 ppm, respectively. Based on the highest relative potency, AL-encapsulated acetamiprid had the most toxicity. The content of energy reserve protein, glucose, and triglyceride and the activity of detoxifying enzymes esterase and glutathione S-transferase of the larvae treated by LC50 values of nanoformulations were also decreased. According to the current findings, the nanoencapsulation of acetamiprid by Al and PEG can increase its insecticidal performance in terms of lethal and sublethal toxicity.

Intraspecific variation in wing geometry among Tabanus rubidus (Diptera: Tabanidae) populations in Thailand.

Tabanus rubidus (Wiedemann, 1821) (Diptera: Tabanidae) is a hematophagous insect of veterinary and medical importance and is the predominant Tabanus spp. in Thailand. It is a potential mechanical vector of Trypanosoma evansi, which causes surra in domestic and wild animals. Wing geometric morphometrics is widely used as morphological markers for species identification and to assess the insect population structure. Herein, we investigated the intraspecific variation in wing geometry among T. rubidus populations in Thailand using landmark-based geometric morphometric analysis. Tabanus rubidus females were collected from five populations in four geographical regions in Thailand. The left wings of 240 specimens were removed and digitized using 22 landmarks for analysis. While wing size variations were found between some populations, wing shape variations were detected in all. These intraspecific variations in T. rubidus populations indicate an adaptive response to the local environmental conditions.