Polyphagous Pest Research Articles

Residual Pattern of Chlorantraniliprole, Thiamethoxam, Flubendiamide and Deltamethrin in Tomato Fruit and Soil.

Tomato, Lycopersicon esculentum L. is grown widely as an important day-to-day demand vegetable. The crop is attacked by various polyphagous insect pests like tomato fruit borer, stink bug, cabbage looper, flea beetle, aphids, whitefly, two-spotted spider mite, etc., and oligophagous insects like leaf-miner, five-spotted hawkmoth, etc. To combat the damage and yield loss, various chemical insecticides were sprayed on tomatoes under field conditions. The residual pattern of insecticides like chlorantraniliprole, thiamethoxam, flubendiamide, and deltamethrin residues was studied following applications of chlorantraniliprole 18.5% SC (Coragen) @ 30g a.i./ha, thiamethoxam 25% WG (Actara) @ 50g a.i./ha, flubendiamide 39.35M/M SC (Fame) @ 48g a.i./ha and deltamethrin 2.8% EC (Decis 100) @ 12.5g a.i./ha using Reverse Phase High-Performance Liquid Chromatography (RP-HPLC). Fruit samples were collected at 0 (1h after application), 1, 2, 3, 5, 7 days and at harvest time. All the residues of insecticides such as chlorantraniliprole (0.09mg kg- 1), thiamethoxam (0.03mg kg- 1), flubendiamide (0.02mg kg- 1), and deltamethrin (0.01mg kg- 1) were persisted up to 5th day. There were no residues found at harvest time. The residues of chlorantraniliprole and deltamethrin persisted up to 3rd day of spraying whereas the residues of flubendiamide and thiamethoxam were not detected on the same day in the soil.

Lethal and sublethal effects of carlina oxide on Tetranychus urticae (Acari: Tetranychidae) and Neoseiulus californicus (Acari: Phytoseiidae).

Tetranychus urticae Koch, is a polyphagous and damaging pest, presenting several resistant populations worldwide. Among new and more environmentally friendly control tools, botanical pesticides represent a valuable alternative to synthetic ones within integrated pest management strategies. Accordingly, we investigated the lethal and sublethal effects of carlina oxide isolated from Carlina acaulis (Asteraceae) roots on T. urticae and its natural enemy, the predatory mite, Neoseiulus californicus (McGregor). Carlina oxide (98.7% pure compound) was used for acaricidal tests on eggs, nymphs, and adult females of T. urticae (concentrations of 312.5, 625, 1250, 2500 and 5000 μL L-1 ), and eggs and females of N. californicus (1250 and 5000 μL L-1 on eggs and females, respectively). Behavioral two-choice tests were also conducted on phytoseiid females. Carlina oxide toxicity was higher on T. urticae females than nymphs (median lethal dose 1145 and 1825 μL L-1 , respectively), whereas egg mortality and mean hatching time were significantly affected by all tested concentrations. A decreasing daily oviposition rate for T. urticae was recorded with concentrations ranging from 625 to 5000 μL L-1 , whereas negative effects on the population growth rate were recorded only with the three higher concentrations (1250, 2500 and 5000 μL L-1 ). No toxic effect on N. californicus females was found, but a strong repellent activity lasting for 48 h from application was recorded. Carlina oxide reduced longevity and fecundity of T. urticae adults, but not of N. californicus. This selective property allows us to propose it as a novel active ingredient of ecofriendly acaricides for T. urticae management. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Insecticidal activities of two fig tree leaf extracts against the cotton pest Spodoptera litura (Fab.) and their impact on the non‐target red worm Eisenia foetida (Savigny)

AbstractExtracts of botanical origin naturally contain a complex mixture of chemicals considered effective in managing lepidopteran pests. Chemical screening of the ethanolic leaf extracts of two fig tree species, Ficus lyrata and Ficus auriculata, delivered 12 and 15 phyto‐compounds with relatively high peak area percentages in phytol and flavone, respectively. Larvicidal activity against Spodoptera litura yielded higher mortality rates at maximum‐concentration treatment (600 ppm) with Ficus lyrata (91.3%) and Ficus auriculata (98.5%) extracts during the second instar. Sub‐lethal dosages (300 ppm) of both Ficus lyrata and Ficus auriculata extracts impeded the development and reproduction of lepidopteran pests. The enzyme‐inhibition activity of both fig extracts elicited a significant reduction in the major digestive enzymes alkaline phosphatase, acid phosphatase, and lactate dehydrogenase dose‐responsively. Mid‐gut histological screening of Ficus lyrata and Ficus auriculata extracts displayed gut lumen disruptions, shape alterations of columnar cells, and brush‐border membrane damage. Further, the non‐target toxicity of fig extracts against the red worm Eisenia foetida was minimal compared with that of the chemical temephos. Overall, the Ficus extracts proved to be eco‐friendly strategies for managing the polyphagous pest Spodoptera litura and are potentially more sustainable and less harmful to non‐target earthworms. Nonetheless, in silico predictions suggest that the active compounds in fig extracts are predominantly toxic against honeybees (16 compounds) and violate TICE rules (10 compounds). Therefore, the biological actions of fig extracts' individual novel chemistries need to be examined on target and non‐target species to develop better pest management strategies.

Insecticidal Activity of Selected Essential Oils against Drosophila suzukii (Diptera: Drosophilidae).

The spotted wing drosophila (SWD), Drosophila suzukii Matsumura (Diptera: Drosophilidae), is an invasive polyphagous pest of soft-skinned fruit that has started to threaten small fruit production in Europe since 2008. High reproductive capacity, short generation time, and difficulties in visualizing early damage contribute to its rapid spread. Currently, the control strategy against D. suzukii mostly relies on treatment with synthetic insecticides. Keeping in mind that this pest causes the greatest damage during the harvesting period, control using chemicals is not recommended due to the increased risk of high pesticide residue levels in the fruit. With the aim of reducing the use of insecticides, there is a need for developing an environmentally safer way of control. Alternative solutions could rely on the use of essential oils (EOs), which can be used in conventional and organic production systems. Four essential oils, geranium (Pelargonium graveolens), dill (Anethum graveolens), Scots pine (Pinus sylvestris), and bergamot (Citrus bergamia), were assessed for their insecticidal effects using four different tests (contact toxicity, fumigant-contact toxicity, repellent effect, and multiple-choice tests). The EOs applied were dissolved in acetone at three different concentrations. The most promising one was the geranium essential oil, which had the best effect in all conducted tests, even at the lowest applied concentration. Geranium oil caused very high mortality (95%), even at the lowest concentration applied, after 24 h in the fumigant-contact test, and it caused a mortality of over 85% in the contact test. It was also noticed that geranium demonstrated a deterrent effect by repelling females from laying eggs for four days after at the lowest applied concentration. Scots pine and dill EOs have moderate to strong effects in most tests. The mortality of 100% was achieved for the highest applied concentration in the fumigant-contact and contact tests. Bergamot EO did not have any significant insecticidal activity. Geranium, Scots pine, and dill have great potential to be used as an environmentally friendly way of controlling D. suzukii as they exhibit deterrent, repellent, and insecticidal effects.

Chromosome-level genome assembly of Bactrocera correcta provides insights into its adaptation and invasion mechanisms

Bactrocera correcta is an invasive polyphagous pest with significant ecological and economic implications. Understanding its genetic characteristics and the molecular mechanisms that drive its rapid adaptation to new environments requires genomic information. In this study, we successfully assembled the chromosome-level genome of B. correcta using PacBio long-read sequencing, Illumina sequencing, and chromatin conformation capture (Hi-C) methods. The final genome assembly spans a total length of 702.65 Mb. We managed to anchor approximately 86.88% of the assembled contigs into 6 linkage groups, ranging from 17.97 Mb to 166.49 Mb. Additionally, our analysis predicted a total of 21,015 genes, with repetitive sequences accounting for 58.22% of the genome. We further identified retroelements and DNA transposons as the major contributors to the larger size of the B. correcta genome, constituting 36.06% and 30.92% of the repetitive sequences, respectively. Our divergence time estimation placed B. correcta's split from other Bactrocera species at around 5.99–16.71 million years ago. Through gene family analyses, we discovered significant expansions in chemosensory-related gene families (IR, GR), heat shock proteins (HSP60), and resistance-related gene families (ABC) in B. correcta compared to its closest relatives. Transcriptomic analysis revealed substantial upregulation of HSP genes, especially those from the HSP20 subfamily, in response to high temperatures. The availability of this reference genome serves as a foundation for the identification of precise target genes in B. correcta, facilitating molecular prevention and control strategies.

The genome of the invasive and broadly polyphagous Diaprepes root weevil, Diaprepes abbreviatus (Coleoptera), reveals an arsenal of putative polysaccharide-degrading enzymes.

The Diaprepes root weevil (DRW), Diaprepes abbreviatus, is a broadly polyphagous invasive pest of agriculture in the southern United States and the Caribbean. Its genome was sequenced, assembled, and annotated to study genomic correlates of specialized plant-feeding and invasiveness and to facilitate the development of new methods for DRW control. The 1.69 Gb D. abbreviatus genome assembly was distributed across 653 contigs, with an N50 of 7.8 Mb and the largest contig of 62 Mb. Most of the genome was comprised of repetitive sequences, with 66.17% in transposable elements, 5.75% in macrosatellites, and 2.06% in microsatellites. Most expected orthologous genes were present and fully assembled, with 99.5% of BUSCO genes present and 1.5% duplicated. One hundred and nine contigs (27.19 Mb) were identified as putative fragments of the X and Y sex chromosomes, and homology assessment with other beetle X chromosomes indicated a possible sex chromosome turnover event. Genome annotation identified 18,412 genes, including 43 putative horizontally transferred (HT) loci. Notably, 258 genes were identified from gene families known to encode plant cell wall degrading enzymes and invertases, including carbohydrate esterases, polysaccharide lyases, and glycoside hydrolases (GH). GH genes were unusually numerous, with 239 putative genes representing 19 GH families. Interestingly, several other beetle species with large numbers of GH genes are (like D. abbreviatus) successful invasive pests of agriculture or forestry.

Development and Validation of a Real-Time PCR for the Molecular Identification of Thaumatotibia leucotreta (Lepidoptera: Tortricidae: Olethreutinae) Intercepted in Trade

The false codling moth, Thaumatotibia leucotreta (Meyrick), is a polyphagous pest indigenous to most of sub-Saharan Africa. This species is considered to be quarantined throughout much of the world, in part due to its extensive host range and significant damage caused by larval feeding. We developed a specific real-time PCR assay that allows for rapid and reliable identification of T. leucotreta. More than 150 target specimens were sequenced using an Illumina whole-genome shotgun approach to identify the most suitable loci for assay development. A hydrolysis probe that binds to a segment of the internal transcribed spacer 2 (ITS2) region was designed and used with a generic internal control targeting 18S rDNA. The assay was examined for cross-reactivity by testing additional Thaumatotibia species and representatives of related Olethreutine leafroller genera such as Cryptophlebia, Cydia, and Grapholita, which are often encountered in the same geographic region and on the same hosts as T. leucotreta. We compared our newly developed test to previously published TaqMan real-time PCR, SYBR Green real-time PCR, and loop-mediated isothermal amplification (LAMP) tests. Our newly developed real-time PCR assay outperformed all three tests in terms of analytical specificity, with 100% accuracy. These results will help to further improve diagnostic standards for molecular identification of T. leucotreta. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Spatiotemporal Patterns of Five Small Heat Shock Protein Genes in Hyphantria cunea in Response to Thermal Stress.

Hyphantria cunea (Drury), a destructive polyphagous pest, has been spreading southward after invading northern China, which indicates that this insect species is facing a huge thermal challenge. Small heat shock proteins (sHSPs) function as ATP-independent molecular chaperones that protect insects from heat stress damage. In order to explore the role of sHSPs in the thermotolerance of H. cunea, five novel sHSP genes of H. cunea were cloned, including an orthologous gene (HcHSP21.4) and four species-specific sHSP genes (HcHSP18.9, HcHSP20.1, HcHSP21.5, and HcHSP29.8). Bioinformatics analysis showed that the proteins encoded by these five HcHSPs contained typical α-crystallin domains. Quantitative real-time PCR analysis revealed the ubiquitous expression of all HcHSPs across all developmental stages of H. cunea, with the highest expression levels in pupae and adults. Four species-specific HcHSPs were sensitive to high temperatures. The expression levels of HcHSPs were significantly up-regulated under heat stress and increased with increasing temperature. The expression levels of HcHSPs in eggs exhibited an initial up-regulation in response to a temperature of 40 °C. In other developmental stages, the transcription of HcHSPs was immediately up-regulated at 30 °C or 35 °C. HcHSPs transcripts were abundant in the cuticle before and after heat shock. The expression of HcHSP21.4 showed weak responses to heat stress and constitutive expression in the tissues tested. These results suggest that most of the HcHSPs are involved in high-temperature response and may also have functions in the normal development and reproduction of H. cunea.

Efficacy of native Bacillus isolates against different larval instars of fall armyworm, Spodoptera frugiperda alone and in combination

BackgroundFall armyworm (FAW) Spodoptera frugiperda (J.E. Smith) Lepidoptera: Noctuidae is an invasive polyphagous pest that causes severe damage to several agricultural crops. The use of pesticides is limited because of their mode of feeding and resistant development. Hence, the present work aimed to determine the pathogenicity of entomopathogenic bacteria (Bacillus spp.) against FAW in terms of mortality and growth inhibition. In this study, initially 49 native Bacillus isolates, isolated from diverse habitats in India, along with five reference strains, were screened for their efficacy against neonates of S. frugiperda under controlled laboratory conditions, followed by virulence and combinatorial bioassays.ResultsFive native Bacillus isolates (VKK1, VKK5, S16C2, S25C1, and SOIL 20) showed mortality in the range of 35.49–65.52% against neonates of S. frugiperda at single concentration (1000 μg g−1 of diet). These five isolates, along with one reference strain Btk-HD1 (Bacillus thuringiensis serovar kurstaki strain HD1), were further tested to find the median lethal concentration (LC50) for neonates of S. frugiperda. Among these, native Bt strain VKK5 showed the lowest LC50 (718.40 µg/g of diet) and HD1 showed the highest LC50 (3352 µg/g of diet). Combinatorial bioassay against neonate and third instar larvae showed that the combination of VKK5 and VKK1 had an additive effect. Moreover, growth inhibition was also recorded.ConclusionThe combination of Bt strains leads to an enhancement of pathogenicity toward FAW larvae at the initial stage of development, and in later stages, it affects their growth and development. Thus, biocontrol of FAW by entomopathogenic bacteria (Bt) can play a vital role in the effective management of FAW.

Molecular identification of the brown marmorated stink bug’s egg parasitoids by species-specific PCR collected from Beijing, China

Brown marmorated stink bug (BMSB), Halyomorpha halys (Stål) (Hemiptera: Penta-tomidae), is a highly polyphagous and invasive insect pest with more than 300 plant species as hosts, including a wide range of economic crops. To date, several egg parasitoid species are reported to attack BMSB. In this study, two species of Trissolcus (Hymenoptera: Platygastridae) and one Anastatus (Hymenoptera: Eupelmidae) were recovered from field exposed BMSB sentinel eggs in Beijing, China. The wasps’ small size of only 1.5 mm and 4 mm in length make them difficult to identify morphologically and required taxonomist for identification of specific species. In addition, these parasitoids have morphology sibling species and have been misidentified several times in China. To overcome these problems, a molecular method with species-specific primers designed for the COI gene has been developed to identify Trissolcus, Anastatus and their host samples from field collected samples. After successful morphological confirmation with experts, DNA extractions were carried out from these samples. PCR amplification using published primers for T. japonicus, A. japonicus and BMSB specimens confirmed the species. As for T. cultratus, species specific primers TCYF and TCYR were developed which produce 340-bp PCR products length while no positive amplifications found in other wasps and host. Sensitivity analysis of markers revealed that TCYF and TCYR primers could detect as low a DNA template concentration as 0.00025 ng/μL. This indicates that PCR with these primers specifically and sensitively differentiates T. cultratus specimens from other similar wasp species. All the primers tested in this study could discriminate between parasitized and non-parasitized BMSB eggs. This molecular identification method shows promise for conveniently identifying Trissolcus and Anastatus species in host-parasitoid associations and accurately evaluating parasitism rates in the field.

Antalya, Karaman ve Muğla’dan belirlenen yeni kayıt afit (Hemiptera: Aphidoidae) türleri

Aphids (Hemiptera: Aphidoidae) are obligatory phytophagous and many of them highly polyphagous pests and distributed almost all parts of the earth, especially temperature zone. Türkiye has a potential area for aphids because of its rich plant diversity and different climatic region. Most of the aphid species is specific to their host plant and both cause direct and indirect damages. So far, 654 aphid species have been determined on numerous host plants in Türkiye. As a result of the study conducted in Antalya, Karaman and Muğla provinces in Türkiye between March 2020 and September 2021, 12 aphid species were added to Türkiye aphidofauna. These species are Amphorophora urtica Essig, 1942 on Urtica dioica L., Aphis crepidis (Börner, 1940) on Crepis capillaris L. (Wallr.), Chaitophorus utahensis (Knowlton, 1928) on Salix sp., Monelliopsis caryae (Monell, 1879) on Juglans regia L., Doraphis populi (Maskell, 1898) on Populus sp., Eulachnus mediterraneus Binazzi, 1983 on Pinus sp., Metopolophium montanum Hille Ris Lambers, 1966 on Rosa sp., Protaphis echinopis (Hille Ris Lambers, 1948) on Echinops viscosus DC., Prociphilus erigeronensis (Thomas, 1879) on Cichorium sp., Sitobion leelamaniae (David, 1958) on Poa sp. and Triticum sp., Tiliaphis pseudoshinae Quednau, 1979 on Tilia sp. and Uroleucon iranicum Holman, 1980 on Gundelia tournefortii (L.). Türkiye aphidofauna has reached 666 species with this study. Detailed information of locality of new records are also given.

Inducible Cytochrome P450s in the Fat Body and Malpighian Tubules of the Polyphagous Pests of Spodoptera litura Confer Xenobiotic Tolerance.

Cytochrome P450 plays vital roles in detoxifying xenobiotics. In this study, SlCYP340A and SlCYP340L expression in the Spodoptera litura fat body and SlCYP332A1, SlCYP6AB12, SlCYP6AB58, SlCYP6AB59, and SlCYP6AN4 expression in the Malpighian tubules were significantly upregulated after cyantraniliprole exposure, and SlCYP6AB58 and SlCYP6AB59 expression levels were simultaneously increased in the Malpighian tubules after gossypol treatment. Drosophila ectopically expressing candidate P450 genes showed that SlCYP332A1, SlCYP6AB12, SlCYP6AB59, SlCYP6AN4, and SlCYP340A conferred cyantraniliprole tolerance. The overexpression of SlCYP6AB58 and SlCYP6AB59 in Drosophila increased the number of eggs laid under the gossypol treatment. Moreover, the knockdown of SlCYP332A1, SlCYP6AB12, SlCYP6AB59, SlCYP6AN4, and SlCYP340A increased S. litura mortality under the cyantraniliprole treatment. Homology modeling and molecular docking results suggested that candidate P450 has the potential to bind with cyantraniliprole. These results indicate that the CYP3 and CYP4 genes participate in cyantraniliprole detoxification and that SlCYP6AB59 may be simultaneously involved in the gossypol tolerance of S. litura.

Pest Status, Bio-Ecology, and Area-Wide Management of Mirids in East Asia.

Mirids (Hemiptera: Heteroptera: Miridae) feed upon a wide variety of cultivated and wild plants and can be economically important crop pests. They have traditionally been perceived as innocuous herbivores in East Asia; however, population levels of various mirid species have dramatically increased over the past decades. High-profile pests such as Apolygus spp., Adelphocoris spp., and Lygus spp. are now widely distributed across the region, and their infestation pressure is associated with climate, agroecological conditions, and farming practices. This review outlines how an in-depth understanding of pest biology, a systems-level characterization of pest ecology, and a comprehensive evaluation of integrated pest management tactics have enabled sustainable management of mirids across crop boundaries and harvest cycles. This work underscores how more holistic, integrative research approaches can accelerate the implementation of area-wide management of generalist pests, effectively prevent pest population build-up and yield impact, and shrink the environmental footprint of agriculture. In addition to highlighting the merits of interdisciplinary systems approaches, we discuss prospects and challenges for the sustainable management of polyphagous mirid pests in landscape matrices.

Organic soil fertility management practices for the management of fall armyworm, Spodoptera frugiperda (J.E. Smith), in maize.

The fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), is a polyphagous pest native to the Americas. It attacks several crops but in particular causes significant damage to maize, which is a staple crop in Africa. Organic soil amendments have an impact on the physical, chemical, and biological properties of soil, which enhance plant resistance to or tolerance of insect pests and also promote a diverse population of natural enemies of the pest. However, the practices followed for the management of crop residue and animal manure affect their use as organic soil amendments. A field experiment was conducted to evaluate the effect of maize residue and cattle manure incorporation into soil on FAW in the Mana and Omo Nada districts of the Jimma zone, southwest Ethiopia, during the 2018/19 cropping season. Treatment involved three factors: five different levels of maize residue retention (0%, 25%, 50%, 75%, and 100%), different cattle manure storage systems (control, open, steel roof, and grass roof), and two different districts (Mana and Omo Nada). These variables were organized in a randomized complete block design and replicated three times. The infestation and damage ratings were collected from 30 days after planting at 20-day intervals. The results indicated that maize plots with retained crop residue had a significant reduction in FAW infestation compared with plots without maize residue (control) in both study districts. Furthermore, manure-fertilized plants had a lower percentage of FAW infestation when compared with maize plots without cattle manure in both study districts. The lowest severity of FAW infestation was recorded in a plot with 100% of residue incorporated and treated with cattle manure stored under a grass roof in the Mana district. Therefore, conventional tillage with 100% maize residue incorporation and the application of cattle manure stored under a grass roof showed the best result for reducing FAW infestation in maize. However, further studies are important to determine the effect of treatments over seasons and locations on FAW infestation and maize yields.

Detection and molecular characterization of Copamyntis obliquifasciella (Hampson, 1896) infesting medicinal plant, Cassia fistula L from India

Cassia fistula L. is a valuable medicinal plant utilized in many traditional medical systems, including Ayurveda and Oriental medicine system. Copamyntis obliquifasciella Hampson (Lepidoptera: Pyralidae) is a polyphagous insect pest, however the available literature of this pest on C. fistula is limited or rather scarce in India as well as world. Considering the economic importance of this medicinal plant, documentation of insects pests along with the bio-ecology and natural enemy fauna is important for formulating the integrated pest management program. The present study describes the incidence, damage and life cycle of C. obliquifasciella on C. fistula in India. The identity of the pest was confirmed through the examination of morphological characteristics of male and female genitalia, further confirmed through molecular analysis (GenBank no. MK559413). The phylogenetic analysis revealed that the Indian population of C. obliquifasciella shared a close relationship with the populations from Pakistan and China. The initial instar larvae of C. obliquifasciella is feed by nibbling and scraping the chlorophyll content of the leaves, and later they stitch two or three leaves together and fed in between those stitched leaves. The percent pest incidence varied between 20 and 100, and the foliar damage of 5.5–71% was recorded. The total life cycle of C. obliquifasciella was completed in 31.20 ± 2.14 (male) and 34.25 ± 2.36 (female) days. Two hymenopteran parasitoids, such as Phanerotoma sp. (Braconidae: Cheloninae) and Apanteles taragamae Viereck (Braconidae: Microgastrinae) were associated with C. obliquifasciella. To best of our knowledge, this is the first description of C. obliquifasciella and their associated natural enemies from the Indian region.

Genetic diversity of the polyphagous pest Rachiplusia nu across crops and locations in the Argentine Pampas

AbstractRachiplusia nu (Guenée) (Lepidoptera: Noctuidae, Plusiinae) is a defoliator of soybean (Glycine max L., Fabaceae), sunflower (Helianthus annuus L., Asteraceae), alfalfa (Medicago sativa L., Fabaceae), and horticultural crops in temperate southern South America; however, there is little genetic information available about this pest insect. Recently, concerns about this insect have increased because of its suspected resistance to Bt soybean and its spread to tropical regions. To better understand pest dynamics, and therefore implement suitable management strategies, a thorough knowledge of the genetic variability and spatial structuring of populations is required. In this paper, R. nu larvae were sampled from various crops and locations in central Argentina (where the pest is endemic) to assess diversity and population structure through mtDNA sequence analysis. In addition to the analysis of the standard cytochrome c oxidase subunit I (COI) ‘barcode’ fragment, a new set of primers was developed to explore genetic variation in the cytochrome b (Cytb) gene. COI and Cytb concatenated sequences revealed an overall high haplotype diversity (mean ± SD = 0.798 ± 0.037) and low nucleotide diversity (0.00137 ± 0.00013). The haplotype network showed a total of 19 haplotypes, separated by at most five mutational steps. A main central haplotype and four additional frequent haplotypes (accounting for 80% of the specimens examined) were distributed across populations with no obvious pattern related to host plant or geographic origin. Analysis of molecular variance further supported a weak population structure, where genetic variation within populations was the main source of total variation (ca. 96%). Pairwise comparisons showed only minor genetic differentiation among some of the populations studied. Implications of these findings in the context of R. nu control are discussed.

Efficacy of Neem and Eucalyptus Leaf Powders for the Management of Maize Weevil Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) in Dried Sweet Potatoes

Maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) is a polyphagous storage pest in many crops of economic and food security importance. Its management currently relies mainly on synthetic chemical pesticides. However, plant botanicals are known to exhibit insecticidal properties which can be used to manage the weevil in stored dry sweet potatoes. To study the effect of neem and eucalyptus leaf powders, an experiment was set up at Busitema University laboratory. Neem and eucalyptus leaves were processed into powders. 400g of dried sweet potato chips were weighed and placed in 4 different plastic buckets. Under laboratory conditions, buckets were inoculated with 30 unsexed newly emerged adult weevils. To each bucket, 40g of leaf powders were introduced as single powders and a combination. The experiment was replicated three times. Data on mortality, growth inhibition, produce damage and weight loss was collected over a period of 84 days. Analysis of variance showed that all plant powders showed significant (P<0.001) increase in mortality and inhibition of maize weevil and a decrease in damage and weight loss of sweet potato compared to control. The combination showed superiority in all parameters measured. Effectiveness of the plant powders was in the order; combination (neem + eucalyptus) > neem leaf powder > eucalyptus leaf powder.

A detoxification pathway initiated by a nuclear receptor TcHR96h in Tetranychus cinnabarinus (Boisduval).

Understanding the mechanism of detoxification initiation in arthropods after pesticide exposure is crucial. Although the identity of transcription factors that induce and regulate the expression of detoxification genes in response to pesticides is beginning to emerge, whether transcription factors directly interact with xenobiotics is unclear. The findings of this study revealed that a nuclear hormone receptor, Tetranychus cinnabarinus hormone receptor (HR) TcHR96h, regulates the overexpression of the detoxification gene TcGSTm02, which is involved in cyflumetofen resistance. The nuclear translocation of TcHR96h increased after cyflumetofen exposure, suggesting direct binding with cyflumetofen. The direct binding of TcHR96h and cyflumetofen was supported by several independent proteomic assays that quantify interactions with small molecules. Together, this study proposes a model for the initiation of xenobiotic detoxification in a polyphagous agricultural pest. These insights not only provide a better understanding of the mechanisms of xenobiotic detoxification and metabolism in arthropods, but also are crucial in understanding adaptation in polyphagous herbivores.

An odorant receptor tuned to an attractive plant volatile vanillin in Spodoptera litura

The insect olfaction plays crucial roles in many important behaviors, in which ORs are key determinants for signal transduction and the olfactory specificity. Spodoptera litura is a typical polyphagous pest, possessing a large repertoire of ORs tuning to broad range of plant odorants. However, the specific functions of those ORs remain mostly unknown. In this study, we functionally characterized one S. litura OR (OR51) that was highly expressed in the adult antennae. First, by using Xenopus oocyte expression and two-electrode voltage clamp recording system (XOE-TEVC), OR51 was found to be strongly and specifically responsive to vanillin (a volatile of S. litura host plants) among 77 tested odorants. Second, electroantennogram (EAG) and Y-tube behavioral experiment showed that vanillin elicited significant EAG response and attraction behavior especially of female adults. This female attraction was further confirmed by the oviposition experiment, in which the soybean plants treated with vanillin were significantly preferred by females for egg-laying. Third, 3D structural modelling and molecular docking were conducted to explore the interaction between OR51 and vanillin, which showed a high affinity (−4.46 kcal/mol) and three residues (Gln163, Phe164 and Ala305) forming hydrogen bonds with vanillin, supporting the specific binding of OR51 to vanillin. In addition, OR51 and its homologs from other seven noctuid species shared high amino acid identities (78–97%) and the same three hydrogen bond forming residues, suggesting a conserved function of the OR in these insects. Taken together, our study provides some new insights into the olfactory mechanisms of host plant finding and suggests potential applications of vanillin in S. litura control.

Microbiome analysis of Spodoptera frugiperda (Lepidoptera, Noctuidae) larvae exposed to Bacillus thuringiensis (Bt) endotoxins.

Spodoptera frugiperda (or fall armyworm, FAW) is a polyphagous pest native to Western Hemisphere and recently discovered in the Eastern Hemisphere. In Colombia, S. frugiperda is recognized as a pest of economic importance in corn. The species has genetically differentiated into two host populations named "corn" and "rice" strains. In 2012, a study made in central Colombia demonstrated that the corn strain is less susceptible to Bacillus thuringiensis (Bt) endotoxins (Cry1Ac and Cry 1Ab) than the rice strain. In this country, Bt transgenic corn has been extensively produced over the last 15 years. Since gut microbiota plays a role in the physiology and immunity of insects, and has been implicated in promoting the insecticidal activity of Bt, in this study an analysis of the interaction between Bt endotoxins and FAW gut microbiota was made. Also, the detection of endosymbionts was performed here, as they might have important implications in the biological control of a pest. The composition and diversity of microbiomes associated with larval specimens of S. frugiperda(corn strain) was investigated in a bioassay based on six treatments in the presence/absence of Bt toxins and antibiotics (Ab) through bacterial isolate analyses and by high throughput sequencing of the bacterial 16S rRNA gene. Additionally, species specific primers were used, to detect endosymbionts from gonads in S. frugiperda corn strain. Firmicutes, Proteobacteria and Bacteroidota were the most dominant bacterial phyla found in S. frugiperda corn strain. No significant differences in bacteria species diversity and richness among the six treatments were found. Two species of Enterococcus spp., E. mundtii and E. casseliflavus were detected in treatments with Bt and antibiotics, suggesting that they are less susceptible to both of them. Additionally, the endosymbiont Arsenophonus was also identified on treatments in presence of Bt and antibiotics. The results obtained here are important since little knowledge exists about the gut microbiota on this pest and its interaction with Bt endotoxins. Previous studies made in Lepidoptera suggest that alteration of gut microbiota can be used to improve the management of pest populations, demonstrating the relevance of the results obtained in this work.