Insect Pests Research Articles

Insecticidal activities of three recombinant venom proteins of the predatory stink bug, Arma custos.

Widespread resistance of insect pests to insecticides and transgenic crops in the field is a significant challenge for sustainable agriculture, and calls for the development of novel alternative strategies to control insect pests. One potential resource for the discovery of novel insecticidal molecules is natural toxins, particularly those derived from the venoms of insect predators. In this study, we identified three insecticidal proteinaceous toxins from the venom glands (VGs) of the predatory stink bug, Arma custos (Hemiptera: Asopinae). Transcriptomic analysis of A. custos VGs revealed 151 potentially secreted VG-rich venom proteins. Three VG-rich venom proteins (designated AcVP1 ~ 3) were produced by overexpression in Escherichia coli. Injection of the recombinant proteins into tobacco cutworm (Spodoptera litura) larvae showed that all of the three recombinant proteins caused paralysis, liquefaction and death. Injection of recombinant proteins into rice brown planthopper (Nilaparvata lugens) nymphs showed higher insecticidal activities, among which a trypsin (AcVP2) caused 100% mortality postinjection at 1.27 pmol mg-1 body weight. A natural toolkit for the discovery of insecticidal toxins from predatory insects has been revealed by the present study. © 2024 Society of Chemical Industry.

Evaluating microbial protein elicitors for managing Cabbage Aphids in Brassica oleracea

Cabbage (Brassica oleracea) is a globally important crop but often suffers from damage caused by sucking insect pests and various diseases. This study explores the effectiveness of microbial protein elicitors, such as PeaT1, PeBL1, Hrip1, and PeBA1, in managing Cabbage aphids (Brevicoryne brassicae). It investigates how these elicitors affect phytohormone pathways, including jasmonic acid, salicylic acid, and ethylene, and examines their impact on leaf structures, particularly trichomes. The research offers a novel approach by thoroughly assessing the mechanisms through which microbial protein elicitors control cabbage aphids. It provides valuable insights into potential new strategies for pest management in agriculture. By clarifying how elicitors interact with aphids, this study contributes to developing sustainable pest control and crop protection methods.

Effect of ozone gas on Attagenus fasciatus (Thunberg) (Coleoptera: Dermestidae) and Gibbium psylloides (Czempinski) (Coleoptera: Ptinidae) as stored silkworm product pests

The insecticidal potential of ozone gas was tested against two insect pests of stored silkworm products, Attagenus fasciatus (Thunberg) (Coleoptera: Dermestidae) and Gibbium psylloides (Czempinski) (Coleoptera: Ptinidae). Ozone was tested at three concentrations, 500, 1000 and 1500 ppmv for three exposure times, 1, 2 and 3 h. The adult mortality of two insects was counted during 7 days of treatment. Changes in the morphological features of two insect's adults were examined under scanning electron microscope (SEM) and the chemical composition of treated silkworm cocoons with ozone was determined. Adult mortality of A. fasciatus and G. psylloides was improved with the increase in ozone concentration and exposure time. Thus, all tested concentrations caused complete adult mortality of A. fasciatus after 3 and 5 days of treatment at two exposure times (2 and 3 h), respectively. While the two concentrations of ozone (1000 and 1500 ppmv) caused full mortality of G. psylloides adults after 5 days of treatments at exposure time 3 h. Examination with SEM of treated adults showed induction malformations on the dorsal surface as split between elytra and between the thorax and elytra as well as a split the head capsule from the thorax. Additionally, there was a decrease in the density of some microtrichiae of A. fasciatus. While in case of G. psylloides, observed induction shrinking and deformities occurred in the abdominal cuticles and the abdomen was exploded as results treating of ozone gas. Furthermore, the chemical composition analysis of treated silkworm cocoons showed a slight decrease in protein and carbohydrate contents and increasing at the fat, moisture, fiber and ash contents. Our results indicated that the ozone gas seems to be a promising fumigant for the control of A. fasciatus and G. psylloides.

Omeprazole and its analogs exhibit insecticidal potencies as inhibitors of insect choline acetyltransferase

Choline acetyltransferase (ChAT) is crucial for acetylcholine synthesis and regulates diverse functions in numerous biological processes. Omeprazole, an inhibitor on human ChAT, was evaluated here on insect ChAT as a potential inhibitor, as well as its insecticidal potency on Nilaparvata lugens, a major insect pest on rice. The evaluation also included omeprazole analogs and α-NETA, in order to explore a superior leading compound targeting on insect ChAT. In toxicity test, α-NETA and omeprazole exhibited insecticidal activity, among which omeprazole exhibited activity with a mortality of around 50 % on N. lugens nymphs at 0.4 mg/mL. In vitro crude enzyme assays showed that omeprazole acted as an inhibitor on insect ChAT with a high selectivity and exciting potency compared with α-NETA and control. Three residues (Tyr84, Val95, Tyr589) was critical in N. lugens ChAT for interacting with its substrate choline through molecular docking, and it also revealed that omeprazole exhibited a higher binding affinity toward ChAT catalytic tunnel compared with α-NETA. Based on this, we screened omeprazole analogs for their affinity to N. lugens ChAT, and two compounds stood out. The 5-hydroxy omeprazole had the highest binding affinity by prediction, and 5-O-desmethyl omeprazole was with the lowest binding affinity. The toxicity bioassay and enzyme activity test were then performed on these two compounds. Aligned with the docking results, 5-hydroxy omeprazole showed a strong inhibitory effect and insecticidal activity. In summary, omeprazole and 5-hydroxy omeprazole could serve as lead compounds for insecticides targeting on insect ChAT, a novel target.

Neem (Azadirachta indica A. Juss; Meliaceae) as the source for plant-based pesticides as an effective and sustainable biocontrol alternative

The neem tree has strengths such as effective and environmentally friendly active compounds, as well as the ability to improve the quality and productivity of plants organically. However, the use of botanical pesticides has several challenges, such as potentially lower effectiveness compared to chemical insecticides, high production costs, and requiring specific knowledge in formulation and application. Botanical pesticides are readily available tools for insect pest management and are eco-friendly. The research results show that a neem formula at a concentration of 20 ml.l-1 water can cause mortality of brown planthopper is 48.75 - 70%, while mortality in the synthetic insecticide (positive control) at a concentration of 2 ml.l-1 water (as recommended) resulted in 45% mortality. It is obvious that there is a need to develop biological control as alternatives for eco-friendly and sustainable for pests’ control in insect’s pest management strategies. This research study has both qualitative and quantitative approach, data collection strategies were desk review of information and will be based on empirical data and literature. For the desk study, relevant internet web pages were browsed to have an overview of the key concepts of the research issue, problem of pests and diseases control and benefit of neem tree as botanical pesticides. Nevertheless, the use of botanical pesticides can provide long-term benefits to the environment and human health and support more sustainable agriculture. There is a great opportunity for the development of more effective and affordable technology for botanical pesticide production for farmers, but there are also threats such as strong competition from synthetic pesticides. The objective this study aims to determine the potential of neem (Azadirachta indica A.Juss) as a plant producing botanical pesticides as an effective and sustainable biological control alternative.

Oral secretions from striped stem borer (Chilo suppressalis) induce defenses in rice.

The striped stem borer (SSB, Chilo suppressalis) is one of the most destructive insect pests on rice. As a chewing insect, SSB larval feeding causes a dramatic increase in rice defense responses. However, the effects of oral secretions (OSs) during SSB feeding on rice defense remain largely unexplored. In this study, based on transcriptome analysis results, treatment with SSB OSs regulated the expression of genes involved in the plant defense-related pathways of calcium, mitogen-activated protein kinases, reactive oxygen species, jasmonic acid (JA), herbivore-induced plant volatiles (HIPVs), and protease inhibitors. Unsurprisingly, treatment with SSB OSs elicited the accumulation of JA and JA-isoleucine in rice. The defense mechanisms activated by the cascade not only induced the expression of trypsin inhibitors, inhibiting the normal growth of SSB larvae but also induced HIPVs emission, rendering rice attractive to a common larval parasitoid. High-throughput proteome sequencing of SSB OSs led to 534 proteins being identified and 343 proteins with two or more unique peptides being detected. The study demonstrates that SSB OSs trigger both direct and indirect defense mechanisms in rice, akin to the effects of SSB feeding. It identifies specific proteins in SSB OSs that may influence the interactions between SSB and rice during feeding, providing valuable insights for effectors research. © 2024 Society of Chemical Industry.

Effect of wheat cultivars, with varying resistance levels to Rhyzopertha dominica, on life history parameters of the ectoparasitoid wasp Anisopteramalus calandrae

The ectoparasitoid wasp Anisopteromalus calandrae (Howard) (Hymenoptera: Pteromalidae), as a widely distributed ectoparasitoid wasp, can parasitize several Coleopteran insect pests such as the lesser grain borer Rhyzopertha dominica (F.) (Coleoptera, Bostrichidae). In the current study, the plant-herbivore-parasitoid interactions with A. calandrae and R. dominica on six cultivars of wheat Triticum aestivum L. (Poals: Poaceae), including Aftab, Araz, Ghabos, Kalateh, Meraj, and Tirgan, were assessed. The largest egg and larval-pupal periods of R. dominica were observed on cultivars Tirgan and Aftab. Rhyzopertha dominica reared on cultivar Araz had the largest total developmental period. The highest oviposition period and fecundity of R. dominica were observed on cultivar Meraj. The pest had the brief life and the low fecundity duration on cultivar Tirgan. The longest developmental time of A. calandrae was observed on the cultivar Tirgan. The parasitic wasp lived longer on cultivar Ghabos. The developmental time of A. calandrae was positively affected by phenolic content of wheat cultivars. The fecundity and intrinsic rate of increase (r) of the parasitic wasp were significantly decreased by increasing the phenolic content of the cultivars. In general, the cultivar Meraj was sensitive, the cultivars Aftab and Kalateh were semi-resistant, and the cultivars Araz, Ghabos, and Tirgan were resistant to R. dominica. The cultivar Tirgan was found as an unsuitable host compared to others for performance of A. calandrae, while Aftab, Kalateh, Araz, and Meraj were suitable ones. Consequently, the use of cultivar Araz as a resistant host to R. dominica and the suitable cultivar to A. calandrae can be considered as an effective integrated management choice against the pest.

Deep-freezing as a novel disinfestation strategy to rice weevil (Sitophilus oryzae Linnaeus) in packaged milled rice grains: Factors and lethal behaviors

Rice weevil (Sitophilus oryzae Linnaeus) is a major insect pest of milled rice grains, which poses a great threat to food security. In this study, the feasibility of three deep-freezing regimes (-20, -80, and -196 oC) to disinfest packaged milled rice grains was explored. It was found that the disinfestation efficiency increased with the decrease in freezing temperature. For naked insects, complete mortality was achieved by the regimes at -20, -80, and -196 oC with the exposure time of 8 min, 2 min, and as short as 1 s, respectively. For insects in packaged rice grains (5 insects/500 g rice; package size: 8 cm × 5 cm × 13 cm), the corresponding exposure time was determined as 100, 40, and 4 min, respectively. Upon the increase in insect population density and package size, the longer exposure time was required for complete mortality. When the regime at -196 oC (1.5 min) was used as a pretreatment at -20 oC (60 min), the highest combination index (2.12) was obtained for the complete mortality. In one word, deep-freezing was successfully developed as a novel method to disinfest adult rice weevil in packaged milled rice grains.

DsRNAPredictor-II: An improved predictor of identifying dsRNA and its silencing efficiency for Tribolium castaneum based on sequence length distribution

RNA interference (RNAi) has been widely utilized to investigate gene functions and has significant potential for control of pest insects. However, recent studies have revealed that the target insect species, dsRNA molecule length, target genes, and other experimental factors can affect the efficiency of RNAi mediated control, restricting the further development and application of this technology. Therefore, the aim of this study was to establish a deep learning model using bioinformatics to help researchers identify dsRNA fragments with the highest RNAi efficiency. In this study, we optimized an existing model, namely, dsRNAPredictor, by designing sub-models based on different sequence lengths. Accordingly, the data were divided into two groups: 130–399 bp and 400–616 bp long sequences. Then, one-hot encoding was employed to extract sequence information. The convolutional neural network framework comprising three convolutional layers, three average pooling layers, a flattened layer, and three dense layers was employed as the classifier. By adjusting the parameters, we established two sub-models for different sequence distributions. Using multiple independent test datasets and conducting hypothesis testing, we demonstrated that our model exhibits superior performance and strong robustness to dsRNAPredictor, respectively. Therefore, our model may help design dsRNAs with pre-screening potential and facilitate further research and applications.

Ex vivo delivery of dsRNA targeting ryanodine receptors for control of Tuta absoluta.

RNA interference (RNAi) is an endogenous eukaryote viral defence mechanism representing a unique form of post-transcriptional gene silencing. Owing to its high specificity, this technology is being developed for use in dsRNA-based biopesticides for control of pest insects. Whilst many lepidopteran species are recalcitrant to RNAi, Tuta absoluta, a polyphagous insect responsible for extensive crop damage, is sensitive. Ryanodine receptors (RyRs) are intracellular calcium channels regulating calcium ion (Ca2+) release. The chemical pesticide class of diamides functions agonistically against lepidopteran RyR, resulting in uncontrolled Ca2+ release, feeding cessation and death. Resistance to diamides has emerged in T. absoluta, derived from RyR point mutations. RNAi was used to target RyR transcripts of T. absoluta. Data presented here demonstrate the systemic use of exogenous T. absoluta RyR-specific (TaRy) dsRNA in tomato plants (Solanum lycopersicum) to significantly downregulate expression of the target gene, resulting in significant insect mortality and reduced leaf damage. Using a leaflet delivery system, daily dosing of 3 μg TaRy dsRNA for 72 h resulted in 50% downregulation of the target gene and 50% reduction in tomato leaf damage. Corrected larval mortality and adult emergence were reduced by 38% and 33%, respectively. TaRy dsRNA demonstrated stability in tomato leaves ≤72 h after dosing. This work identifies TaRy as a promising target for RNAi control of this widespread crop pest. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Detection and functional validation of point mutations in acetylcholinesterase-1 associated with organophosphate resistance in field populations of Helicoverpa armigera.

Point mutations in the acetylcholinesterase-1 gene (ace-1) have been associated with resistance to OPs in many insects. However, the presence and function of ace-1 mutations associated with OP resistance in Helicoverpa armigera (Lepidoptera: Noctuidae), a significant lepidopteran pest damaging a wide range of crops, remain largely unexplored. This study investigated resistance to the OP insecticide phoxim in 12 field populations of H. armigera from northern China in 2022, revealing low levels of resistance (2.5- to 6.7-fold). Using an amplicon sequencing approach, we screened for ace-1 mutations in 13,874 moths collected from 114 populations collected between 2006 and 2022. We found 3 amino acid substitutions (A201S, G227E, and F290V) potentially related to OP resistance. The mean frequencies of A201S, G227E, and F290V mutations were 0.0032, 0.0001, and 0.0001, respectively. To assess these mutations' role in OP resistance, we expressed wild-type and mutant AChE1 proteins in Sf9 cells. Biochemical characterization revealed a 3.1-fold and 3.3-fold increase in the I50 of chlorpyrifos-oxon for A201S and F290V mutants compared to the wild-type enzyme, correlating with a 2.9-fold and 2.7-fold decrease in the Ki value. No enzyme activity was observed in the G227E mutant, indicating that only A201S and F290V confer insensitivity to chlorpyrifos-oxon. Our study demonstrates that amplicon sequencing is an effective method for large-scale screening of resistance-associated point mutations in field populations of H. armigera and potentially other insect pests. It also identifies A201S and F290V in AChE1 as potential point mutations conferring OP resistance in field populations of H. armigera.

Isolation and characterization of halophilic Bacillus thuringiensis from local Egyptian sites and their potential against Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae)

Abstract Background Bacillus thuringiensis (Bt) serves as a peculiar soil microbe that is Gram-positive, rod-shaped, spore-forming, and aerobic facultative. It endures across a range of conditions and has been demonstrated to be an effective biological pest control agent against several insect pests. The main objective of the study is to isolate and recognize Bt bacteria from saline environments in Egyptian soil for biological surveillance uses. Results Isolates three, four, five, ten, eleven, twelve, and thirteen were found to be moderately tolerant, while isolate eight showed highly tolerant, but isolate six was found to be borderline extreme halophile. On the other hand, the other isolates showed extreme halophiles. To find out the presence of crystals, a scanning electron microscope was carried out and the result showed that the crystals ranged from spherical to bi-pyramidal spherical. Molecular analysis was carried out using universal primers to confirm the presence of cry genes. The results showed that 84.6% of the isolates contain cry seven and eight, whereas cry one and four are distributed by 92.3%. Cry two genes were found to be 100 percent in all tested and isolated cultures. Cry genes were present and distribution among isolated was detected using gene-specific primers. cry3Ba1 and cry8B showed the lowest and equal distribution among the isolates, while the cry2Ab2gene frequency distribution was (84.6%) among isolated cultures. Around six cry genes were found to be absent in all isolated cultures. The bioinsecticidal activity and bioassays were carried out to check the potential effect of halophilic Bt isolates against 1st instar larvae of the Fall Armyworm (FAW) Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae). Mortality was calculated after infecting S. frugiperda with thirteen Bt isolates. The most virulent Bt isolate was isolate 7, followed by isolate 10, with LC50 values of 9.542 × 107 spores/ml and 1.289 × 108 spores/ml, respectively, after 72 h. Morphological traits of the larvae were carried out, to check the effect of Bt isolates as a biological control against the FAW. Conclusion To protect and enhance the sustainability of field crops and vegetables, especially in new high salinity lands, from disease-causing insects such as FAW, it is necessary to identify new strains of Bt from these saline lands. In this field, local isolates of Bt from several regions in Egypt known for their high levels of salinity were documented and showed an effective bioinsecticide on FAW larvae.

Cereal aphid species: their natural enemies and efficiency of Lysiphlebus testaceipes (Cresson, 1880) to control Rhopalosiphum maidis (Fitch, 1856)

AbstractCereal grains both for human consumption and animal feed are an essential component of global food systems. However, during production they are often targeted by various pest insects, including aphids. A survey was carried out from 2017 to 2021 in six cereal production sites in Tunisia to evaluate aphid diversity and identify natural enemies on Triticum turgidum subsp. durum (durum wheat), Hordeum vulgare (barley), Avena sativa (oat) and Triticum secale (triticale). Six aphid species belonging to four genera were recorded: Diuraphis noxia, Rhopalosiphum maidis, R. padi, Schizaphis graminum, Sitobion avenae and Sitobion fragariae. Among these, S. avenae and R. padi emerged as the most prevalent species across the majority of sites, infesting durum wheat, barley and triticale. Sc. graminum, R. maidis and D. noxia were less frequent, while S. fragariae was exclusively found on oat plants. Common aphid predators observed included Coccinella algerica, Hippodamia variegata and C. undecimpunctata, as well as syrphid flies such as Episyrphus balteatus and Sphaerophoria rueppellii. Lysiphlebus testaceipes was the sole parasitoid species detected, emerging exclusively from R. padi and R. maidis mummies. Furthermore, the study on the efficacy of L. testaceipes against R. maidis indicated that parasitism levels increased with the number of introduced parasitoid pairs. Aphid and natural enemy diversity were also evaluated.

Seven New Species of Anastatus Motschulsky (Hymenoptera: Chalcidoidea: Eupelmidae) from China Identified Based on Morphological and Molecular Data

Anastatus is the second-largest genus in the family Eupelmidae, with 150 species found worldwide and fourteen known species in China. Most species in this genus are the primary parasitoids of insect eggs, particularly those of Lepidoptera and Hemiptera, and several species have been used for the biological control of various insect pests. In this paper, seven new species of Anastatus Motschulsky, 1859 (Hymenoptera: Eupelmidae) from China are described, of which A. caeruleus Wang and Peng n. sp. and A. garygibsoni Zhou and Peng n. sp. were reared from the eggs of Tessaratoma papillosa (Hemiptera: Tessaratomidae), while A. daiyunensis Wang and Peng n. sp., A. makrysourus Zhou and Peng n. sp., A. polikiarkoudus Wang and Peng n. sp., A. taibaiensis Wang and Peng n. sp., and A. zdenekbouceki Zhou and Peng n. sp. were collected by malaise traps or sweeping. The new species are all described and illustrated based on female specimens, and the key to all 21 Chinese Anastatus species, based on females, is provided. Partial COI sequences of A. caeruleus n. sp., A. garygibsoni n. sp., and A. taibaiensis n. sp. are provided, and a phylogenetic reconstruction based on maximum likelihood analyses, while showing similar results at high taxonomic levels to our morphological feature classification results, provides additional information on the placement of Anastatus at the species level.

Analyses of Xenorhabdus griffiniae genomes reveal two distinct sub-species that display intra-species variation due to prophages.

Nematodes of the genus Steinernema and their Xenorhabdus bacterial symbionts are lethal entomopathogens that are useful in the biocontrol of insect pests, as sources of diverse natural products, and as research models for mutualism and parasitism. Xenorhabdus play a central role in all aspects of the Steinernema lifecycle, and a deeper understanding of their genomes therefore has the potential to spur advances in each of these applications. Here, we report a comparative genomics analysis of Xenorhabdus griffiniae, including the symbiont of Steinernema hermaphroditum nematodes, for which genetic and genomic tools are being developed. We sequenced and assembled circularized genomes for three Xenorhabdus strains: HGB2511, ID10 and TH1. We then determined their relationships to other Xenorhabdus and delineated their species via phylogenomic analyses, concluding that HGB2511 and ID10 are Xenorhabdus griffiniae while TH1 is a novel species. These additions to the existing X. griffiniae landscape further allowed for the identification of two subspecies within the clade. Consistent with other Xenorhabdus, the analysed X. griffiniae genomes each encode a wide array of antimicrobials and virulence-related proteins. Comparative genomic analyses, including the creation of a pangenome, revealed that a large amount of the intraspecies variation in X. griffiniae is contained within the mobilome and attributable to prophage loci. In addition, CRISPR arrays, secondary metabolite potential and toxin genes all varied among strains within the X. griffiniae species. Our findings suggest that phage-related genes drive the genomic diversity in closely related Xenorhabdus symbionts, and that these may underlie some of the traits most associated with the lifestyle and survival of entomopathogenic nematodes and their bacteria: virulence and competition. This study establishes a broad knowledge base for further exploration of not only the relationships between X. griffiniae species and their nematode hosts but also the molecular mechanisms that underlie their entomopathogenic lifestyle.

Survey on Influence of Cultural Practices on Banana Pseudostem Weevil, Odoiporus longicollis Olivier (Coleoptera: Curculionidae) Infestation in Major Banana Growing Districts of Northern Karnataka, India

The production and productivity of banana is governed by many biotic and abiotic factors. Among biotic factors, incidence of insect-pests is considered as one of the major impedimentin successful cultivation of banana. With respect to the Indian condition around eight pests commonly infest the banana crop. However, the banana pseudostem weevil Odoiporus longicollis is cosmopolite insect pest that threatens the banana cultivation. The most common management practices followed for managing this pest includes cultural practices. Diverse cultural practices have been communicated to and/or applied by resource-poor households over the past two decades to improve the overall farm health and crop tolerance to biotic/abiotic factors. Therefore, cultural practices are the only measures available to small-scale farmers for the control of banana pseudostem weevil. Hence the survey was conducted during 2020-21 to study the influence of cultural practices on O. longicollis infestation in major banana growing districts of north Karnataka. From the survey results on the cultural practices reveals that the pest severity was more severe on ratoon crop fields and the frequency recorded was 37.82%. However, the frequency recorded was 1.68% in first crop, wherein no pest infestation was recorded in main crop. Whereas, good number of farmers could not make a difference in infestation of pest between main and ratoon crop (60.50%) and in such fields infestation level was 4.11%. The banana farmers who were interacted mainly used suckers (36.13%) and tissue culture plants (36.13%) for planting followed by rhizome (24.37%), whereas few farmers used suckers and rhizomes (3.36%) for planting in a single piece of land. Accordingly, the per cent infestation of BPW was less when both tissue cultured plants (4.84%) and suckers (5.53%) used for planting. Whereas, infestation was more severe when both suckers and rhizomes were used (27.50%) on same piece of land and which was followed by rhizomes alone (16.00%).

Evaluating the attractiveness of different bait formulations for monitoring Liriomyza sativae (Diptera: Agromyzidae) adults

The growing need for sustainable agricultural practices drives the search for effective alternatives in pest management. Insects like Liriomyza sativae cause significant damage to crops, requiring monitoring and control methods that minimize the use of chemical pesticides. In this context, the use of natural and synthetic attractants for pest capture offers a promising solution while contributing to the preservation of ecological balance. The objective of this work was to study the attractive effect of different formulations for L. sativae adults. The formulations were divided into two groups according to their composition. For group 1, they were based on vinegar and sugar, and for group 2, formulations were based on molasses, invert sugar, hydrolyzed protein, and eugenold. The attractiveness of the formulations was evaluated based on free choice. They were placed in tube-shaped plastic containers and randomly arranged in TNT cages. Evaluations were performed every 48 hours by counting the number of adults in the containers until there was a low capture rate. Data were subjected to analysis of variance testing and means were compared using the Scott-Knott test at 5% significance level. All formulations tested were attractive to adults of L. sativae, with groups 1 and 2 reaching their maximum averages of 55.60 and 68.00 adults, respectively. Both occurred during the second evaluation. Over time, all formulations showed a reduction in capture rate. The use of effective attractants promotes traps that monitor and even control the pest population in a more sustainable way, benefiting the agroecosystem with sustainable agricultural practices. Furthermore, the research expands knowledge about the chemical ecology of insect pests, providing a basis for the chemical communication of these organisms.

Salivary effector DcE1 suppresses plant defense and facilitates the successful feeding of Asian citrus psyllid, Diaphorina citri.

Piercing-sucking insects secrete diverse repertoires of effectors into their hosts to weaken host defenses and promote infestation. The Asian citrus psyllid, Diaphorina citri Kuwayama, is the most destructive insect pest in citrus orchards because of its role as a vector for the huanglongbing pathogen, Candidatus Liberibacter asiaticus (CLas). However, specific effector proteins and their functions in D. citri remain unclear. We demonstrate that DcE1, a salivary protein gene from D. citri, is predominantly expressed in the salivary gland tissues and is delivered into host plants during feeding. Transient expression in tobacco leaves revealed that DcE1 was subcellularly localized in the cytoplasm and plasma membrane, where it inhibited BAX- and INF1-induced cell death, suppressed callose deposition, and activated the salicylic acid pathway by upregulating the expression of endo-β-1,3-glucanase NtBGL2 and regulatory protein NtNPR1. Further, DcE1 knockdown by double-stranded RNA (dsRNA) injection decreased the survival rates of D. citri and interrupted D. citri phloem-feeding on host plants. These results indicate that DcE1 is a novel effector that promotes plant susceptibility and enables D. citri feeding. These findings enhance our understanding of D. citri-plant interactions and offer a potential new target gene for the development of citrus protection strategies. © 2024 Society of Chemical Industry.

Efficacy and utility of isocycloseram a novel isoxazoline insecticide against urban pests and public health disease vectors.

Isoxazolines inhibit γ-aminobutyric acid chloride channels in insects and acarids by binding to postsynaptic receptors. This prevents chloride influx, leading to depolarization/hyperexcitation, paralysis, and death. Here, we evaluated the potential utility of a novel isoxazoline, isocycloseram, against several urban insect pests. Isocycloseram was active at low doses against the German cockroach, Blattella germanica (L.)[median lethal dose (LD50) 5-15 ng per insect at 72 h, topical assays]; Argentine ant (Linepithema humile Mayr), Pharaoh ant (Monomorium pharaonis (L.), common bed bug (Cimex lectularius (L.) (approximately 40 mg m-2, residual surface spray); Eastern subterranean termite (Reticulitermes flavipes (Kollar)and Formosan subterranean termite (Coptotermes formosanus Shiraki) (5 μg g-1 w/w, tunneling assays); and mosquito, Anopheles stephensi Liston (120 and 150 mg m-2 treated surfaces, aged indoors for 9 months). Additionally, cockroach gel bait at 1% isocycloseram (w/w) caused 95-100% mortality in German, American (Periplaneta americana (L.), and oriental (Blatta orientalis (L.) cockroaches within 5-14 days. Isocycloseram proved to be active against both laboratory and field populations of German cockroaches at doses lower or equal to those of other chemicals. Ants, bed bugs, and mosquitoes readily acquired lethal doses of isocycloseram from different surfaces treated with formulated products. Given its non-repellent nature, delayed effects, and activity at low rates, isocycloseram can be a very effective compound against subsocial, social, and other human disease vector insect pests. © 2024 Society of Chemical Industry.

Sublethal effects of neonicotinoids on insect pests

Sublethal effects of neonicotinoids on insect pests