Pest Control Strategies Research Articles

Larval instars determination for the twig borer weevil (Coleoptera: Curculionidae) of Falcataria moluccana (Miq.) Barneby & Grimes in Moluccas, Indonesia

In establishing an integrated pest control strategy, it is important first to discover the life history of a potential agent, including the number of larval instars. The snout-weevil of the tribe Ithyporini Genus species (Coleoptera: Curculionidae) is a holometabolous insect that attacks Falcataria moluccana, a native tree of the Moluccas (Maluku), Indonesia. Preliminary observations show that their larvae feed and develop as a twig borer, making direct observation of their development complicated. This study aimed to determine the number of larval instars by measuring the head capsule width (HCW) and the growth pattern of larvae. As many as 940 larvae of all sizes were collected from three islands in Maluku Province: Ambon, Seram, and Haruku. Kernel density estimation (KDE) and Gaussian mixture model (GMM) were used for data analysis. The growth instars were verified using Brooks-Dyar’s rule. The results indicated four peaks in the frequency distribution from KDE, and cluster four showed the best-fit model from GMM. The growth ratio of HCW was 1.47, which also agrees with Brooks-Dyar’s rule that the growth ratio was consistent and followed a constant geometric. Thus, this research concluded that there were four instars for Ithyporini Gen. sp. larvae.

The Relationship Between Tomato Yellow Leaf Curl Virus Resistance Gene and Root Knot Nematode Meloidogyne spp. Resistance Gene in Tomato Plants

Tomato Mi-1.2 resists root-knot nematodes. Mi, or a similar gene, may also be responsible for resistance to Bemisia tabaci whitefly in Mi-bearing commercial tomato varieties. Mi-1.2 is the only resistance gene that fights root-knot nematodes, aphids, and whiteflies. Mi is useful in integrated pest control strategies because these pests are the most damaging to tomato crops worldwide. Ten tomato varieties were produced to determine which are resistant to TYLCV and the root-knot nematode Meloidogyne spp. and whether these genes are linked. TYLCV-free nurseries were used to grow these tomato varieties. To assess these cultivars’ sensitivity and resistance to TYLCV, they were transferred to the plastic house and planted during Bemisia tabaci insect activity. These types were planted in soil contaminated with nematode eggs and juvenal, vaccinated, and reported every 15 days for disease incidence. Class H cultivars were vulnerable to nematodes and the virus, while class Gres were TYLCV-resistant. The rest of the cultivars were TYLCV-resistant, nematode-resistant, or both.

Sustainable Strategies for the Control of Pests in Coffee Crops

Coffee is a worldwide commodity, and both coffee-producing and coffee-consuming countries have real concerns about environmental problems and economic growth strategies based on the efficient use of resources. Because this crop is a perennial, pests can significantly affect coffee production, causing considerable yield losses and threatening coffee supply and security. The presence of insects and control strategies for coffee pests is becoming a challenge. Environmental sustainability, conservation of biodiversity, and safety of the coffee seed must go hand in hand with the economic sustainability of coffee growers. This is especially important, as there has been an increase in demand for coffee and new consumer interest in differentiated quality coffee. Regular pest control methods based only on the use of synthetic pesticides are no longer effective or sustainable due to the development of insecticide resistance and negative effects on the environment, human health, and biodiversity. Thus, to ensure better control and ecological sustainability, it is crucial to reduce pesticide use by adopting original alternative strategies to maintain pest populations below the economic threshold level and towards reaching the European Green Deal. In this review, we collect information available for sustainable control of the principal coffee pests in Colombia: coffee berry borer (CBB), Hypothenemus hampei; Monalonion velezangeli; coffee root mealybugs; coffee leaf miner: Leucoptera coffeella; and the coffee red spider mite: Oligonychus yothersi. The control strategies include deep knowledge of the biology of insects and the coffee plant, their relationship with weather and habitats, as well as natural controllers. These control strategies do not involve the use of insecticides, are ecologically friendly and novel, and can be applied in other coffee-producing countries.

The Orco gene involved in recognition of host plant volatiles and sex pheromone in the chive maggot Bradysia odoriphaga

The insect olfactory recognition system plays a crucial role in the feeding and reproductive behaviors of insects. The odorant receptor co-receptor (Orco), as an obligatory chaperone, is critical for odorant recognition by way of forming heteromeric complexes with conventional odorant receptors (ORs). To investigate the biological functions of Orco in perceiving host plant volatiles and sex pheromone, the Orco gene was identified from the chive maggot Bradysia odoriphaga transcriptome data. Multiple sequence alignment reveals that BodoOrco exhibits an extremely high sequence identity with Orcos from other dipteran insects. The expression of BodoOrco is significantly higher in adults than in larvae and pupae, and the BodoOrco gene is primarily expressed in the antennae of both sexes. Furthermore, the Y-tube assay indicated that knockdown of BodoOrco leads to significant reductions in B. odoriphaga adults' response to all tested host plant volatiles. The dsOrco-treated unmated male adults show less attraction to unmated females and responded slowly compared with dsGFP control group. These results indicated that BodoOrco is involved in recognition of sex pheromone and host plant volatiles in B. odoriphaga and has the potential to be used as a target for the design of novel active compounds for developing ecofriendly pest control strategies.

Comparative Analysis of the Metabolic Profiles of Strains of Tribolium castaneum (Herbst) Adults with Different Levels of Phosphine Resistance Based on Direct Immersion Solid-Phase Microextraction and Gas Chromatography-Mass Spectrometry

The management of phosphine (PH3) resistance in stored grain pests is an essential component of implementing timely and effective pest control strategies. The prevailing standard method for PH3 resistance testing involves the exposure of adult insects to a specific concentration over a fixed period. Although it is widely adopted, this method necessitates an extensive period for assay preparation and diagnosis. To address this issue, this study employed Direct Immersion Solid-Phase Microextraction (DI-SPME) coupled with Gas Chromatography-Mass Spectrometry (GC-MS) to compare and analyze the metabolic profiles of PH3-sensitive (TC-S), PH3 weak-resistant (TC-W), and PH3 strong-resistant (TC-SR) Tribolium castaneum (Herbst) adults. A total of 36 metabolites were identified from 3 different PH3-resistant strains of T. castaneum; 29 metabolites were found to present significant differences (p < 0.05) across these groups, with hydrocarbon and aromatic compounds being particularly prevalent. Seven metabolites showed no significant variations among the strains, consisting of four hydrocarbon compounds, two iodo-hydrocarbon compounds, and one alcohol compound. Further multivariate statistical analysis revealed a total of three, two, and nine differentially regulated metabolites between the TC-S versus TC-W, TC-S versus TC-SR, and TC-W versus TC-SR groups, respectively. Primarily, these metabolites comprised hydrocarbons and iodo-hydrocarbons, with the majority being associated with insect cuticle metabolism. This study demonstrates that DI-SPME technology is an effective method for studying differentially expressed metabolites in T. castaneum with different levels of PH3 resistance. This approach may help to provide a better understanding of the development of insect PH3 resistance and act as a valuable reference for the establishment of rapid diagnostic techniques for insect PH3 resistance.

Role of phytochemicals and secondary metabolites from Mentha spicata in acetylcholine esterase inhibition for effective pest control of Tetranychus urticae Koch

ABSTRACTThe two-spotted spider mite (Tetranychus urticae Koch) poses a significant threat to global food production. However, the environmental risks associated with synthetic pesticides have necessitated the exploration of eco-friendly alternatives. Plant-based biopesticides utilizing secondary metabolites have emerged as promising strategies for pest management. This study aimed to extract and characterize Mentha spicata L. through biochemical analyses, GC-MS, and LC-QTOF-MS. The extract’s acaricidal, oviposition deterrence, and repellent properties were evaluated against Tetranychus urticae, revealing a pronounced time- and concentration-dependent effect over 96 hours, with an LC50 of 3 µg/mL. Furthermore, the impact of the extract on plant growth was assessed using tomato plants, demonstrating an enhancement in growth rate based on photosynthesis, weight, and oxidative stress markers analyses. Polyphenolics and terpenoids in M. spicata were identified as contributors to its biological activities, including antioxidant and free-radical scavenging properties. Molecular docking experiments targeting acetylcholine esterase (AChE) were conducted on the identified phytocompounds, indicating a high affinity for δ-3-Carene and Isoferuloyl C1 glucuronide. The pesticidal effects of these compounds were attributed to their competitive and synergistic inhibition of AChE. These findings highlight the potential of plant extracts, specifically M. spicata, as effective biopesticides in future pest control strategies. The utilization of secondary metabolites from plant sources offers a sustainable and environmentally friendly approach to combatting T. urticae infestations.

An Assessment of the Impact of Climate Change on Pest Infestation and Control Methods

Climate change has pervasive effects on agriculture, impacting various facets of production. The production of agricultural commodities is particularly susceptible to the influence of climate change. This is exemplified by the escalating losses incurred due to pests, which in turn, pose a significant threat to global food security. Notably, for every degree rise in temperature, insect predators are responsible for a substantial 10–25% reduction in production output. Climate change further exacerbates the situation by bolstering the diffusion, longevity, and adaptability of these pests. Alterations in temperature patterns lead to shifts in weather dynamics, while the emission of chemicals into the atmosphere induces noteworthy changes in the distribution, migration, and behavioral patterns of insect predators. Consequently, this exerts a palpable impact on the overall volume of sustenance generated worldwide. The predicament of crop infestations by insects and the resulting production losses is already a pressing concern for major agricultural powerhouses such as China, the United States, and France. This article delves into a comprehensive assessment of the repercussions of climate change on pest infestations, along with an exploration of viable pest control strategies.

Impact of Temperature on Insect Behavior in India

Purpose: The aim of the study was to investigate the Impact of Temperature on Insect Behavior in India.
 Methodology: The study adopted a desktop methodology. Desk research refers to secondary data or that which can be collected without fieldwork. Desk research is basically involved in collecting data from existing resources hence it is often considered a low cost technique as compared to field research, as the main cost is involved in executive’s time, telephone charges and directories. Thus, the study relied on already published studies, reports and statistics. This secondary data was easily accessed through the online journals and library
 Findings: Research on the impact of temperature on insect behavior in India has demonstrated significant findings. As temperatures continue to rise due to climate change, insects are exhibiting altered behaviors, affecting various ecosystems and agricultural practices. Studies indicate shifts in the timing of insect life cycles, including altered breeding patterns and earlier emergence from diapause. Additionally, rising temperatures have been associated with increased insect pest activity, posing threats to crop yields and ecosystem dynamics. These findings underscore the need for proactive measures to mitigate the consequences of changing insect behaviors in India, including adaptive agricultural strategies and ecosystem management practices.
 Unique Contribution to Theory, Practice and Policy: The Degree-Day Theory, Temperature-Dependent Activity Theory and Optimal Foraging Theory may be used to anchor future studies on the Impact of Temperature on Insect Behavior in India. Pest control strategies should be tailored to account for temperature-dependent shifts in insect activity patterns, thereby optimizing the timing and choice of control measures. Policymakers should recognize the critical role of temperature in shaping insect behavior and its cascading effects on ecosystems, food security, and public health.
 Keywords: Temperature, Insect, Behavior 
 ©2023 by the Authors. This Article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0

Evaluation of different high doses aqueous plant extracts for the sustainable control of Aedes aegypti mosquitoes under laboratory conditions

Aedes aegypti mosquitoes represent a significant public health hazard as they serve as vectors for a variety of arboviral infections, including Dengue, Zika, and Chikungunya. This necessitates the development of efficacious vector control strategies. The current study conducted at the Medical Entomology laboratory of the Nuclear Institute for Food and Agriculture (NIFA) Peshawar, Pakistan, evaluated the potential use of locally sourced aqueous-based plant extracts against different life stages of Aedes aegypti mosquitoes. The utilization of plant extracts, including Parthenium hysterophorus, Nicotiana tabacum, Melia azedarach, and Fagonia indica, offers a potentially effective and ecologically sustainable strategy for pest control. The above excerpts present environmentally friendly alternatives that are biodegradable and have a little impact on the environment. These alternatives are in contrast to synthetic pesticides and contribute to the promotion of sustainable and ecologically responsible methods of pest control. The study tested various plant extracts, specifically those from Parthenium hysterophorus, Nicotiana tabacum, Melia azedarach, and Fagonia indica. These were examined at high concentrations to assess their toxicity to the mosquito species. The extract of P. hysterophorus demonstrated impressive efficacy, displaying 100 % effectiveness across all mosquito life stages. This was closely followed by N. tabacum, F. indica, and M. azedarach in decreasing order of efficacy. To better understand the potency of these plant extracts, their LC50 values were determined after 24, 48, and 72 h post-exposure. LC50 values, a common measure in toxicology, indicate the concentration at which 50 % of the test organisms are killed. Among the tested extracts, M. azedarach exhibited the highest LC50 values (1.703 %, 2.142 %, 2.640 %), implying lower toxicity, while P. hysterophorus showed the lowest LC50 values (0.120 %, 0.420 %, 0.975 %), indicating high toxicity to Aedes aegypti mosquito larvae. Based on the comparative analysis of toxicity, the extracts' efficiency order was established as follows: P. hysterophorus extracts > N. tabacum extracts > F. indica extracts > M. azedarach extracts. These findings suggest that P. hysterophorus and N. tabacum, particularly at a 3 % concentration, hold promising potential as components in eco-friendly integrated vector management (IVM) strategies. This approach would serve as an alternative to the traditional reliance on synthetic pesticides, which often pose environmental and health risks due to their residual toxicity.

Population dynamics and insecticide resistance in Tuta absoluta (Lepidoptera: Gelechiidae), an invasive pest on tomato in Kenya

Tuta absoluta feeds on solanaceous plants with preference on tomato. Management of the pest is mostly with chemical insecticides. This study identified insecticide resistant populations and predicted resistance to insecticides. Insecticide resistance development was modelled using system thinking, and system dynamics approaches. The model showed the pest resistance development is alarming with an exponential increase of the resistance strength mostly in recent years. Furthermore, we used seven insecticide-resistance gene markers to resolve the population structure and genetic differentiation of insecticide-resistant populations in Kenya. The genes for resistance (knockdown resistance (kdr) mutations, acetylcholinesterase (AChE) and voltage gated sodium channel (para)) were detected in all populations. Population structure analyses separated T. absoluta populations into three genetic clusters with resistant genes that are interconnected. A better insight on the population dynamics and the genetic structure T. absoluta resistant genes in Kenya will help estimate resistance strength and determine the most effective pest control strategies.

Silencing the rhythm gene AgCLK-1 reduced feeding of Aphis gossypii

The cotton aphid Aphis gossypii Glover is an important cotton pest, and means of controlling this insect is a primary research focus. Although biological rhythm is an important mechanism that regulates numerous insect processes and activities, its role in cotton aphid has not been elucidated. In the present study, four highly-expressed circadian rhythm genes were selected from the cotton aphid genome database and their physicochemical properties and protein structures were analyzed. These genes were in the Takeout, Timeless, and Timeless interacting-related families, and the corresponding proteins contained highly-conserved Swis and TIMELESS domains. Gene expression analysis at multiple developmental stages revealed differing expression patterns between the four genes. AgCLK-1 had the highest relative expression of the four, especially during the nymph period. Silencing AgCLK-1 caused a significant refusal of the cotton aphids to feed at 1, 3, and 5 d of treatment. These results demonstrated that AgCLK-1 played a key role in regulating the feeding behavior of cotton aphid. This new functional understanding provides novel insights into cotton aphid biology and suggests new targeting strategies for agricultural pest control.

Does monitoring pests pay off? a bioeconomic assessment of Drosophila suzukii controls.

Drosophila suzukii is a significant invasive pest that has caused high management costs and economic losses for blueberry growers in the United States. The status quo control strategy commonly used by growers is to apply pesticides proactively and frequently to reduce infestation. Recent studies have shown that the calendar-based spraying strategy might be unsustainable in the long term, making the reduction of pesticide reliance a top priority for the berry industry. Incorporating pest monitoring into the control strategy could be an option to improve efficiency while reducing pesticide usage. This study assesses the economic implications of monitoring-based control strategies compared to calendar-based spraying control strategies for organic blueberry production in Oregon. We combine a D. suzukii population model into the economic simulation framework, evaluate two monitoring methods (adult trapping and fruit sampling), and identify the profit-maximizing control strategy under different scenarios. In the baseline scenario, control strategies that incorporate fruit sampling exhibit the highest average profits. Although the status quo control strategy (spraying every 3 days) generates higher average revenue than monitoring-based strategies, the cost from the higher number of pesticide application offsets the returns. This study uses a novel bioeconomic simulation framework to show that incorporating fruit sampling can be a promising tool to reduce pesticide reliance while controlling D. suzukii infestation. These findings provide clearer information on the economic viability of using monitoring-based pest control strategies in organic berry production, and the assessment framework sheds light on the economics of pest management. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Effective delivery and selective insecticidal activity of double-stranded RNA via complexation with diblock copolymer varies with polymer block composition.

Chemical insecticides are an important tool to control damaging pest infestations. However, lack of species specificity, the rise of resistance and the demand for biological alternatives with improved ecotoxicity profiles means that chemicals with new modes of action are required. RNA interference (RNAi)-based strategies using double-stranded RNA (dsRNA) as a species-specific bio-insecticide offer an exquisite solution that addresses these issues. Many species, such as the fruit pest Drosophila suzukii, do not exhibit RNAi when dsRNA is orally administered due to degradation by gut nucleases and slow cellular uptake pathways. Thus, delivery vehicles that protect and deliver dsRNA are highly desirable. In this work, we demonstrate the complexation of D. suzukii-specific dsRNA for degradation of vha26 mRNA with bespoke diblock copolymers. We study the ex vivo protection of dsRNA against enzymatic degradation by gut enzymes, which demonstrates the efficiency of this system. Flow cytometry then investigates the cellular uptake of Cy3-labelled dsRNA, showing a 10-fold increase in the mean fluorescence intensity of cells treated with polyplexes. The polymer/dsRNA polyplexes induced a significant 87% decrease in the odds of survival of D. suzukii larvae following oral feeding only when formed with a diblock copolymer containing a long neutral block length (1:2 cationic block/neutral block). However, there was no toxicity when fed to the closely related Drosophila melanogaster. We provide evidence that dsRNA complexation with diblock copolymers is a promising strategy for RNAi-based species-specific pest control, but optimisation of polymer composition is essential for RNAi success. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The Effect of Cuelure on Attracting and Feeding Behavior in Zeugodacus tau (Walker) (Diptera: Tephritidae).

As a vital pest control strategy, trapping plays an important role in the system of monitoring, catching and killing fruit flies. Cuelure (4-(4-acetoxyphenyl)-2-butanone, CL) is a male lure that attracts Zeugodacus tau and also stimulates feeding in this species. In this study, the attraction of Z. tau to CL and its subsequent feeding behavior were investigated. Under the significant influence of age and time of day, the attraction of CL to Z. tau was found to be optimal when flies were 14 days old, and the number of flies trapped increased with trapping duration. It was determined that consumption can improve the mating success and female adult fertility of Z. tau. After the observation period, the mating success rate of flies that ingested CL was significantly higher than that of the control group and was maintained at a higher level. It was found that parental consumption of CL could accelerate the development of eggs and larvae, resulting in increased pupation and emergence rates. The results of this study will further clarify the dynamic relationship between pest and lure, and provide a research basis for navigating the integrated management of Z. tau in the field.

In vitro efficacy of Boswellia carterii resin extracts formulated as an emulsifiable concentrate against Tetranychus urticae and phytopathogenic fungi

Contemporary agriculture heavily relies on pesticides for pest eradication and disease management. Consequently, current study was carried out to assess the acaricidal/antifungal efficacy of emulsifiable concentrate (10 % EC) derived from Boswellia carterii (B. carterii) against adult females of Tetranychus urticae (T. urticae), and five fungal pathogens. The meticulous examination of the chemical constitution of the crude extracts derived from the resin of B. carterii was conducted through the employment of the venerable technique known as Gas-Liquid Chromatography (GLC). The formulated petroleum-ether extract (FPEE) and formulated ethyl-acetate extract (FEAE) of B. carterii at a concentration of 10 mg ml−1 exhibited notable antioxidant activity with rates of 62.0 % and 90.8 %, respectively. In vitro, the FEAE exhibited potent inhibition against all the tested phytopathogenic fungi at different concentrations, whereas FPEE showed comparatively less efficacy. Interestingly, at 4000 ppm concentration, FEAE completely ceased the mycelial growth compared with the control. Moreover, following a span of 72 h of intervention, FPEE exhibited a greater degree of toxicity towards mature females of the T. urticae. This was evidenced by the LC50 value of 422.52 parts per million (ppm) for FPEE, which surpassed the LC50 value of 539.50 ppm observed for FEAE. In summary, the present study indicates that B. carterii resin formulated as an emulsifiable concentrate (10 % EC) can offer a natural and effective alternative for integrated pest management, thereby reducing reliance on synthetic pesticides and offering a more environmentally sustainable strategy for pest control.

Exploring the Significance of Insects in Ecosystems: A Comprehensive Examination of Entomological Studies

The dynamic and expansive field of entomology is poised for transformative changes, thanks to technological advancements and the emergence of new avenues of research. Traditional methodologies like specimen collection and observation are increasingly being complemented by state-of-the-art techniques such as environmental DNA (eDNA) analysis, CRISPR genome editing, remote sensing, and artificial intelligence. The eDNA methodology, for example, offers a non-invasive approach to monitor elusive or endangered insect species, thereby enriching biodiversity databases. Genome editing technologies like CRISPR have enabled nuanced manipulation of insect genes, providing a deeper understanding of their physiology and behavior. Moreover, artificial intelligence and machine learning contribute to automated species identification and predictive modeling of insect populations, offering invaluable insights for conservation efforts. In terms of emerging fields, insect neurobiology, microbiomics, and environmental entomology are gaining prominence. Neurobiological studies are dissecting the neural substrates of insect behaviors, which not only deepen our basic biological understanding but also have implications in robotics and AI. Microbiomics explores the symbiotic relationships between insects and their microbial communities, revealing avenues for novel pest control strategies. Environmental entomology focuses on the impacts of habitat change and climate variability on insect populations, which is crucial for biodiversity conservation. Acknowledging the concerted efforts of researchers, academic institutions, and funding bodies is essential, as these stakeholders shape the field's future direction. Thus, entomology stands at the cusp of a new era, enriched by technological innovations and multidisciplinary approaches. These advancements hold the promise of significantly broadening our understanding of insects' roles in ecosystems, their adaptability, and their importance in maintaining ecological balance. This future direction not only provides exciting prospects for scientific inquiry but also brings forth substantial implications for the sustainable management of ecosystems and conservation policy.

Molecular mechanism of sex pheromone perception in male Mythimna loreyi revealed by in vitro system.

Mythimna loreyi is an important agricultural pest with a sensitive sex pheromone communication system. To clarify the pheromone binding proteins (PBPs) and pheromone receptors (PRs) involved in sex pheromone perception is important for both understanding the molecular olfactory mechanism and developing a new pest control strategy in M. loreyi. First, the electroantennogram (EAG) assay showed that male M. loreyi displayed the highest response to the major sex pheromone component Z9-14:Ac, and higher responses to two minor components, Z7-12:Ac and Z11-16:Ac. Second, the fluorescence competition binding assay showed that PBP1 bound all three pheromones and other tested compounds with high or moderate affinity, while PBP2 and PBP3 each bound only one pheromone component and few other compounds. Third, functional study using the Xenopus oocyte system demonstrated that, of the six candidate PRs, PR2 was weakly sensitive to the major pheromone Z9-14:Ac, but was strongly sensitive to pheromone analog Z9-14:OH; PR3 was strongly and specifically sensitive to a minor component Z7-12:Ac; PR4 and OR33 were both weakly sensitive to another minor component, Z11-16:Ac. Finally, phylogenetic relationship and ligand profiles of PRs were compared among six species from two closely related genera Mythimna and Spodoptera, suggesting functional shifts of M. loreyi PRs toward Spodoptera PRs. Functional differentiations were revealed among three PBPs and six PRs in sex pheromone perception, laying an important basis for understanding the molecular mechanism of sex pheromone perception and for developing new control strategies in M. loreyi. © 2023 Society of Chemical Industry.

Fusion dsRNA in targeting salivary protein genes enhance the RNAi-based aphid control

RNA interference (RNAi) is a promising tool for pest control and relies on sequence-specific gene silencing. Salivary proteins are cooperatively secreted into plants to guarantee the feeding of aphids; thus they have potential to develop as selective targets for RNAi-based pest control strategy. For this purpose, we firstly analyzed 18 salivary proteomes of various aphid species, and these salivary proteins can be mainly categorized into seven functional groups. Secondly, we created a work-flow for fusion dsRNA design that can target multiple genes but were selectively safe to beneficial insects. Based on this approach, seven fusion dsRNAs were designed to feed the green peach aphid, which induced a significant reduction in aphid fitness. Among them, ingestion of dsperoxidase induced the highest mortality in aphids, which was also significantly higher than that of traditional dsRNAs in targeting three peroxidases separately. In addition, dsperoxidase-fed green peach aphids triggered the highest H2O2 content of host plants as well as the attraction to natural enemies (ladybeetle and parasitic wasp) but repellent to other control aphids. Our results indicate that the fusion dsRNA design approach can improve aphid control capacity, and the fusion dsRNA targeting salivary protein-encoding genes can enhance the direct and indirect defenses of host plants, thus providing a new strategy for RNAi-based aphid control.

Dynamic analysis and control of a rice-pest system under transcritical bifurcations.

A decision model is developed by adopting two control techniques, combining cultural methods and pesticides in a hybrid approach. To control the adverse effects in the long term and to be able to evaluate the extensive use of pesticides on the environment and nearby ecosystems, the novel decision model assumes the use of pesticides only in an emergency situation. We, therefore, formulate a rice-pest-control model by rigorously modelling a rice-pest system and including the decision model and control techniques. The model is then extended to become an optimal control system with an objective function that minimizes the annual losses of rice by controlling insect pest infestations and simultaneously reduce the adverse impacts of pesticides on the environment and nearby ecosystems. This rice-pest-control model is verified by analysis, obtains the necessary conditions for optimality, and confirms our main results numerically. The rice-pest system is verified by stability analysis at equilibrium points and shows transcritical bifurcations indicative of acceptable thresholds for insect pests to demonstrate the pest control strategy.

Involvement of cyclic nucleotide-gated channels in soybean cyst nematode chemotaxis and thermotaxis

The soybean cyst nematode (SCN) is one of the most damaging pests affecting soybean production. SCN displays important host recognition behaviors, such as hatching and infection, by recognizing several compounds produced by the host. Therefore, controlling SCN behaviors such as chemotaxis and thermotaxis is an attractive pest control strategy. In this study, we found that cyclic nucleotide-gated channels (CNG channels) regulate SCN chemotaxis and thermotaxis and Hg-tax-2, a gene encoding a CNG channel, is an important regulator of SCN behavior. Gene silencing of Hg-tax-2 and treatment with a CNG channel inhibitor reduced the attraction of second-stage juveniles to nitrate, an attractant with a different recognition mechanism from the host-derived chemoattractant(s), and to host soybean roots, as well as their avoidance behavior toward high temperatures. Co-treatment of ds Hg-tax-2 with the CNG channel inhibitor indicated that Hg-tax-2 is a major regulator of SCN chemotaxis and thermotaxis. These results suggest new avenues for research on control of SCN.