Insect Pest Control Strategies Research Articles

Alcohol dehydrogenase 5 of Helicoverpa armigera interacts with the CYP6B6 promoter in response to 2-tridecanone.

Alcohol dehydrogenase 5 (ADH5) is a member of medium‐chain dehydrogenase/reductase family and takes part in cellular formaldehyde and S‐nitrosoglutathione metabolic network. 2‐tridecanone (2‐TD) is a toxic compound in many Solanaceae crops to defend against a variety of herbivory insects. In the broader context of insect development and pest control strategies, this study investigates how a new ADH5 from Helicoverpa armigera (HaADH5) regulates the expression of CYP6B6, a gene involved in molting and metamorphosis, in response to 2‐TD treatment. Cloning of the HaADH5 complementary DNA sequence revealed that its 1002 bp open reading frame encodes 334 amino acids with a predicted molecular weight of 36.5 kD. HaADH5 protein was purified in the Escherichia coli Transetta (pET32a‐HaADH5) strain using a prokaryotic expression system. The ability of HaADH5 protein to interact with the 2‐TD responsive region within the promoter of CYP6B6 was confirmed by an in vitro electrophoretic mobility shift assay and transcription activity validation in yeast. Finally, the expression levels of both HaADH5 and CYP6B6 were found to be significantly decreased in the midgut of 6th instar larvae after 48 h of treatment with 10 mg/g 2‐TD artificial diet. These results indicate that upon 2‐TD treatment of cotton bollworm, HaADH5 regulates the expression of CYP6B6 by interacting with its promoter. As HaADH5 regulation of CYP6B6 expression may contribute to the larval xenobiotic detoxification, molting and metamorphosis, HaADH5 is a candidate target for controlling the growth and development of cotton bollworm.

Plant Health Newsletter: Media Monitoring No. 8

EFSA Supporting PublicationsVolume 16, Issue 9 1317E Plant Health NewsletterOpen Access Plant Health Newsletter: Media Monitoring No. 8 European Food Safety Authority (EFSA), European Food Safety Authority (EFSA)Search for more papers by this author European Food Safety Authority (EFSA), European Food Safety Authority (EFSA)Search for more papers by this author First published: 13 September 2019 https://doi.org/10.2903/sp.efsa.2019.EN-1317 Question number: EFSA-Q-2017-00519 Compiled in November 2017 AboutPDF ToolsExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat References Arora AK & Douglas AE (2017) Hype or opportunity? Using microbial symbionts in novel strategies for insect pest control. Journal of Insect Physiology 103: 10– 17. http://dx.doi.org/10.1016/j.jinsphys.2017.09.011 Volume16, Issue9September 20191317E This article also appears in:Horizon Scanning for Plant Health ReferencesRelatedInformation

A Review of the Bioactivity of Plant Products Against Aedes aegypti (Diptera: Culicidae)

Abstract The mosquito Aedes aegypti L. (Diptera: Culicidae) is a disease vector for several pathogens that affect human health worldwide. Therefore, there is a need to produce synthetic chemicals that can effectively control mosquitoes; however, these chemicals can also cause a range of environmental and health problems. In the present review, we compiled all available information from the literature between 2005 and 2018 on plant products that have been used to control A. aegypti and tabulated their modes of action. This review classifies these plant-based products according to their bioactivities (toxicity, repellency, feeding deterrence, and oviposition deterrence) and provides new insights, findings, and patterns of their application. Plants contain a wide spectrum of chemical compounds that can effectively control mosquito populations; therefore, they should be developed to control diseases transmitted by mosquitoes. Plant products are mostly safe for human, animal, and environmental health. Moreover, because of the diversity and low use of plant-derived compounds as insect control agents, mosquitoes have not acquired resistance to them. The present review indicated that the bioactivities of many plant compounds can effectively control A. aegypti in laboratory conditions, and the comprehensive cataloging and classification of natural plant product bioactivities in this review will facilitate the search for new applications of these substances in insect pest control strategies.

Glucosylation of (Z)-3-hexenol informs intraspecies interactions in plants: A case study in Camellia sinensis.

Plants emit a variety of volatiles in response to herbivore attack, and (Z)-3-hexenol and its glycosides have been shown to function as defence compounds. Although the ability to incorporate and convert (Z)-3-hexenol to glycosides is widely conserved in plants, the enzymes responsible for the glycosylation of (Z)-3-hexenol remained unknown until today. In this study, uridine-diphosphate-dependent glycosyltransferase (UGT) candidate genes were selected by correlation analysis and their response to airborne (Z)-3-hexenol, which has been shown to be taken up by the tea plant. The allelic proteins UGT85A53-1 and UGT85A53-2 showed the highest activity towards (Z)-3-hexenol and are distinct from UGT85A53-3, which displayed a similar catalytic efficiency for (Z)-3-hexenol and nerol. A single amino acid exchange E59D enhanced the activity towards (Z)-3-hexenol, whereas a L445M mutation reduced the catalytic activity towards all substrates tested. Transient overexpression of CsUGT85A53-1 in tobacco significantly increased the level of (Z)-3-hexenyl glucoside. The functional characterization of CsUGT85A53 as a (Z)-3-hexenol UGT not only provides the foundation for the biotechnological production of (Z)-3-hexenyl glucoside but also delivers insights for the development of novel insect pest control strategies in tea plant and might be generally applicable to other plants.

Distinct binding affinities of odorant-binding proteins from the natural predator Chrysoperla sinica suggest different strategies to hunt prey

Chrysoperla sinica is an important natural predator of many notorious agricultural pests. Understanding its olfactory mechanism can help enhance the effectiveness of C. sinica in biological control. In the present study, we investigated the tissue expression patterns of 12 odorant-binding protein (OBP) genes from C. sinica (CsinOBPs). The results of quantitative real-time polymerase chain reaction (qPCR) showed that CsinOBP1, CsinOBP2, CsinOBP3, CsinOBP4, CsinOBP6, CsinOBP7, CsinOBP9, CsinOBP10, and CsinOBP12 were predominantly expressed in the antennae of both sexes, indicating their roles in olfaction. Additionally, the qPCR analysis revealed that the 12 CsinOBP genes had distinct expression patterns, while the motif-pattern investigation suggested that the OBPs had different ligands. The ligand-binding assay showed that CsinOBP1 and CsinOBP10 had broader binding spectra than did the other OBPs. Thus, CsinOBP1 was able to bind not only plant volatiles (such as farnesol, cis-3-hexenyl hexanoate, geranylacetone, β-ionone, 2-tridecanone, and trans-nerolidol) but also the aphid alarm pheromone (E)-β-farnesene. On the other hand, CsinOBP2 and CsinOBP6 exhibited relatively narrow binding spectra, only binding ethyl benzoate. The study also identified several compounds that can potentially be used to develop slow-release agents attracting C. sinica and to improve search strategies for insect pest control.

Evaluating trap cropping strategies for insect pest control through simulation models

Fil: Fenoglio, Maria Silvina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Cordoba. Instituto Multidisciplinario de Biologia Vegetal. Universidad Nacional de Cordoba. Facultad de Ciencias Exactas Fisicas y Naturales. Instituto Multidisciplinario de Biologia Vegetal; Argentina

Diversity and phylogenetic analysis of endosymbiotic bacteria of the date palm root borer Oryctes agamemnon (Coleoptera: Scarabaeidae).

BackgroundThe date palm root borer Oryctes agamemnon (Coleoptera: Scarabaeidae) is one of the major pests of palms. In Saudi Arabia, both larvae and adults of Oryctes are particularly troublesome, especially during the establishment of young date palm orchards. Endosymbiotic bacteria are known to have a key role in food digestion and insecticide resistance mechanisms, and therefore are essential to their host insect. Identification of these bacteria in their insect host can lead to development of new insect pest control strategies.ResultsMetagenomic DNA from larval midgut of the date palm root borer, O. agamemnon, was analyzed for endosymbiotic bacterial communities using denatured gradient gel electrophoresis (DGGE) utilizing 16S rRNA genes. The DGGE fingerprints with metagenomic DNA showed predominance of eleven major operational taxonomic units (OTUs) identified as members of Photobacterium, Vibrio, Allomonas, Shewanella, Cellulomonas, and Citrobacter, as well as uncultured bacteria, including some uncultured Vibrio members. DGGE profiles also showed shifts in the dominant bacterial populations of the original soil compared with those that existed in the larval midguts. The endosymbiotic bacterial community was dominated by members of the family Vibrionaceae (54.5%), followed by uncultured bacteria (18.2%), Enterobacteriaceae (9.1%), Shewanellaceae (9.1%), and Cellulomonadaceae (9.1%). Phylogenetic studies confirmed the affiliation of the dominant OTUs into specified families revealed by clustering of each phylotype to its corresponding clade. Relative frequency of each phylotype in larval midguts revealed predominance of Vibrio furnisii and Vibrio navarrensis, followed by uncultured bacterial spp., then Cellulomonas hominis, Shewanella algae, and Citrobacter freundii.ConclusionAnalysis of metagenomic DNA for endosymbiotic bacterial communities from the midgut of Oryctes larvae showed strong selection of specific bacterial populations that may have a key role in digestion, as well as other benefits to the larvae of O. agamemnon. Determination of the distinct endosymbiotic community structure and its possible biological functions within the insect could provide us with basic information for future pest control research.

How insects survive desiccation and cold

Peptides designed on the basis of capa, which controls insect renal tubule function, may provide new strategies for insect pest control.

Sugarcane giant borer transcriptome analysis and identification of genes related to digestion.

Sugarcane is a widely cultivated plant that serves primarily as a source of sugar and ethanol. Its annual yield can be significantly reduced by the action of several insect pests including the sugarcane giant borer (Telchin licus licus), a lepidopteran that presents a long life cycle and which efforts to control it using pesticides have been inefficient. Although its economical relevance, only a few DNA sequences are available for this species in the GenBank. Pyrosequencing technology was used to investigate the transcriptome of several developmental stages of the insect. To maximize transcript diversity, a pool of total RNA was extracted from whole body insects and used to construct a normalized cDNA database. Sequencing produced over 650,000 reads, which were de novo assembled to generate a reference library of 23,824 contigs. After quality score and annotation, 43% of the contigs had at least one BLAST hit against the NCBI non-redundant database, and 40% showed similarities with the lepidopteran Bombyx mori. In a further analysis, we conducted a comparison with Manduca sexta midgut sequences to identify transcripts of genes involved in digestion. Of these transcripts, many presented an expansion or depletion in gene number, compared to B. mori genome. From the sugarcane giant borer (SGB) transcriptome, a number of aminopeptidase N (APN) cDNAs were characterized based on homology to those reported as Cry toxin receptors. This is the first report that provides a large-scale EST database for the species. Transcriptome analysis will certainly be useful to identify novel developmental genes, to better understand the insect’s biology and to guide the development of new strategies for insect-pest control.

Insecticidal activity of plant lectins and potential application in crop protection.

Lectins constitute a complex group of proteins found in different organisms. These proteins constitute an important field for research, as their structural diversity and affinity for several carbohydrates makes them suitable for numerous biological applications. This review addresses the classification and insecticidal activities of plant lectins, providing an overview of the applicability of these proteins in crop protection. The likely target sites in insect tissues, the mode of action of these proteins, as well as the use of lectins as biotechnological tools for pest control are also described. The use of initial bioassays employing artificial diets has led to the most recent advances in this field, such as plant breeding and the construction of fusion proteins, using lectins for targeting the delivery of toxins and to potentiate expected insecticide effects. Based on the data presented, we emphasize the contribution that plant lectins may make as tools for the development of integrated insect pest control strategies.

Strategy for Insect Pest Control in Cocoa

Farming systems in cocoa over the last three decades have involved the use of new hybrid plant varieties, which produce pods throughout the year, intensified fertilizer use, and misguided pesticide applications by some farmers. Resource availability in terms of abundance of feeding and breeding sites and ecological disruption as a consequence of climate change and bad agronomic practices have increased the importance of insect pests on cocoa. Historically the major management tool for hemipteran pests has been calendar spraying with conventional insecticides. Considerable progress was made at the turn of the last century by replacing organochlorine insecticides for cocoa mirid control. But inappropriate timing and inefficient application is probably reducing the viability of otherwise acceptable products in some areas. Integrated Pest Management (IPM) strategy for mirids and other insect control should involve great investment in pest surveillance, and be based primarily on the use of cultural practices of removal of excess chupons, shade management and Opinion Article Adu-Acheampong et al.; AJEA, 6(6): 416-423, 2015; Article no.AJEA.2015.099 417 host variety resistance. These practices must primarily aim at minimising mirid-associated dieback disease and stink bug deformation of pods, and should be supplemented in some cases by the use of insecticides (up to two applications in February to May at 28-days intervals) depending on the pest populations, damage levels as well as intensity of activity of pollinating insects, with additional two applications during September to December when pest problems may arise. Improved methods of monitoring and prediction should assist in early identification of specific problems in different farms. The rotational use of different active ingredients should also take into account factors such as application methods, compatibility and correct timing. Careful planning is necessary to formulate a flexible control system.

Insect trehalase: physiological significance and potential applications.

Trehalose, a non-reducing disaccharide, is widespread throughout the biological world. It is the major blood sugar in insects playing a crucial role as an instant source of energy and in dealing with abiotic stresses. The hydrolysis of trehalose is under the enzymatic control of trehalase. The enzyme trehalase is gaining interest in insect physiology as it regulates energy metabolism and glucose generation via trehalose catabolism. The two forms of insect trehalase namely, Tre-1 and Tre-2, are important in energy supply, growth, metamorphosis, stress recovery, chitin synthesis and insect flight. Insect trehalase has not been reviewed in depth and the information available is quite scattered. The present mini review discusses our recent understanding of the regulation, mechanism and biochemical characterization of insect trehalase with respect to its physiological role in vital life functions. We also highlight the molecular and biochemical properties of insect trehalase that makes it amenable to competitive inhibition by most glycosidase inhibitors. Due to its crucial role in carbon metabolism in insects, application of inhibitors against trehalose can form a promising area towards formulating strategies for insect pest control.

Identification, functional characterization and phylogenetic analysis of double stranded RNA degrading enzymes present in the gut of the desert locust, Schistocerca gregaria

RNA interference (RNAi) has become a widely used reverse genetics tool in eukaryotes and holds great potential to contribute to the development of novel strategies for insect pest control. While previous studies clearly demonstrated that injection of dsRNA into the body cavity of the desert locust, Schistocerca gregaria, is highly effective to induce gene silencing effects, we observed that the RNAi response is much less sensitive to orally delivered dsRNA. In line with this, we report on the presence of a potent dsRNA degrading activity in the midgut juice. Four different dsRNase sequences that belong to the DNA/RNA Non-specific Nuclease superfamily were retrieved from a transcriptome database of the desert locust. Surprisingly, we have found that, in the publicly available eukaryote nucleotide sequence databases, the presence of this group of enzymes is restricted to insects and crustaceans. Nonetheless, phylogenetic analyses predict a common origin of these enzymes with the Endonuclease G (EndoG) Non-specific Nucleases that display a widespread taxonomic distribution. Moreover, in contrast to the Sg-endoG transcript, the four Sg-dsRNase transcripts appear to be specifically expressed in the gut. Finally, by means of RNAi, we provide evidence for an important contribution of dsRNase2 to the dsRNA degrading activity that is present in the gut lumen of S. gregaria.

Bugs in Transition: The Dynamic World of Wolbachia in Insects

Bugs in Transition: The Dynamic World of Wolbachia in Insects

RNA‐sequencing analysis reveals abundant developmental stage‐specific and immunity‐related genes in the pollen beetle Meligethes aeneus

The pollen beetle (Meligethes aeneus) is a major pest of oilseed rape (Brassica napus) and other cruciferous crops in Europe. Pesticide-resistant pollen beetle populations are emerging, increasing the economic impact of this species. We isolated total RNA from the larval and adult stages, the latter either naïve or immunized by injection with bacteria and yeast. High-throughput RNA sequencing (RNA-Seq) was carried out to establish a comprehensive transcriptome catalogue and to screen for developmental stage-specific and immunity-related transcripts. We assembled the transcriptome de novo by combining sequence tags from all developmental stages and treatments. Gene expression data based on normalized read counts revealed several functional gene categories that were differentially expressed between larvae and adults, particularly genes associated with digestion and detoxification that were induced in larvae, and genes associated with reproduction and environmental signalling that were induced in adults. We also identified many genes associated with microbe recognition, immunity-related signalling and defence effectors, such as antimicrobial peptides (AMPs) and lysozymes. Digital gene expression analysis revealed significant differences in the profile of AMPs expressed in larvae, naïve adults and immune-challenged adults, providing insight into the steady-state differences between developmental stages and the complex transcriptional remodelling that occurs following the induction of immunity. Our data provide insight into the adaptive mechanisms used by phytophagous insects and could lead to the development of more effective control strategies for insect pests.

Inducible expression of a fusion gene encoding two proteinase inhibitors leads to insect and pathogen resistance in transgenic rice

Plant proteinase inhibitors (PIs) are considered as candidates for increased insect resistance in transgenic plants. Insect adaptation to PI ingestion might, however, compromise the benefits received by transgenic expression of PIs. In this study, the maize proteinase inhibitor (MPI), an inhibitor of insect serine proteinases, and the potato carboxypeptidase inhibitor (PCI) were fused into a single open reading frame and introduced into rice plants. The two PIs were linked using either the processing site of the Bacillus thuringiensis Cry1B precursor protein or the 2A sequence from the foot-and-mouth disease virus (FMDV). Expression of each fusion gene was driven by the wound- and pathogen-inducible mpi promoter. The mpi-pci fusion gene was stably inherited for at least three generations with no penalty on plant phenotype. An important reduction in larval weight of Chilo suppressalis fed on mpi-pci rice, compared with larvae fed on wild-type plants, was observed. Expression of the mpi-pci fusion gene confers resistance to C.suppressalis (striped stem borer), one of the most important insect pest of rice. The mpi-pci expression systems described may represent a suitable strategy for insect pest control, better than strategies based on the use of single PI genes, by preventing insect adaptive responses. The rice plants expressing the mpi-pci fusion gene also showed enhanced resistance to infection by the fungus Magnaporthe oryzae, the causal agent of the rice blast disease. Our results illustrate the usefulness of the inducible expression of the mpi-pci fusion gene for dual resistance against insects and pathogens in rice plants.

Comparison of the effects of three plant protein inhibitors on α-glucosidase of Sunn pest, Eurygaster integriceps Putton

The Sunn pest is a serious pest of wheat and the other cereals. In this study, the effects of proteinaceous extracts of chickpea, bean and rice against the Sunn pest α-glucosidase was investigated. Results showed that chickpea seed extract has an inhibitory effect on α-glucosidase activity of the Sunn pest gut but bean and rice seed extracts did not affect the enzyme activity. The effects of various concentrations of chickpea seed extract on α-glucosidase activity of gut were dose dependant. There were significant differences between the control and different treatments. Also, results showed that the effect of chickpea seed extracts on the α-glucosidase of the Sunn pest gut was pH dependant. Thus, our results showed that chickpea seed extract, but not bean and rice seed extract, has biological activity against the Sunn pest α-glucosidase and it could contribute towards the development of new insect pest control strategies.

Cover Caption

RNA interference (RNAi) has been considered as a potential strategy for insect pest control especially for sucking insects, for example, planthoppers, aphids and psyllids. Metamorphosis is a unique developmental model of insects. Therefore, using RNAi technology, regulating the key genes during insect growth and development will not affect other organisms. This strategy probably realizes biological and ecological safety of insect pest control. Photo in cover shows a brown planthopper Nilaparvata lugens molting. Photo provided by Prof. Xue‐Xia Miao.

Feasibility, limitation and possible solutions of RNAi‐based technology for insect pest control

Numerous studies indicate that target gene silencing by RNA interference (RNAi) could lead to insect death. This phenomenon has been considered as a potential strategy for insect pest control, and it is termed RNAi-mediated crop protection. However, there are many limitations using RNAi-based technology for pest control, with the effectiveness target gene selection and reliable double-strand RNA (dsRNA) delivery being two of the major challenges. With respect to target gene selection, at present, the use of homologous genes and genome-scale high-throughput screening are the main strategies adopted by researchers. Once the target gene is identified, dsRNA can be delivered by micro-injection or by feeding as a dietary component. However, micro-injection, which is the most common method, can only be used in laboratory experiments. Expression of dsRNAs directed against insect genes in transgenic plants and spraying dsRNA reagents have been shown to induce RNAi effects on target insects. Hence, RNAi-mediated crop protection has been considered as a potential new-generation technology for pest control, or as a complementary method of existing pest control strategies; however, further development to improve the efficacy of protection and range of species affected is necessary. In this review, we have summarized current research on RNAi-based technology for pest insect management. Current progress has proven that RNAi technology has the potential to be a tool for designing a new generation of insect control measures. To accelerate its practical application in crop protection, further study on dsRNA uptake mechanisms based on the knowledge of insect physiology and biochemistry is needed.

Effect of irradiation and insect pest control on rots and sensory quality of two varieties of stored ware white yams in Ghana

The coffee bean weevil, Araecerus fasciculatus Degeer (Coleoptera: Curculionidae) is associated with rots in stored yam tubers. The current study was designed to assess the effect of irradiation and other insect pest control strategies on rots and sensory quality of stored yams. 450 tubers each of two varieties of white yam (Dioscorea rotundata Poir) namely ‘Puna’ and ‘Asana’ were divided into two groups with half irradiated and the other half not irradiated. The two groups were then further divided into three sub-groups. The first sub-group was treated with a chemical insecticide ‘Superguard’ (400g/l Pirimiphos-methyl and 75 g/l Permethrin) against A. fasciculatus infestation whilst the second sub-group was placed in insect-proof boxes with no chemical treatment. The third sub-group was neither chemically treated nor placed in insect-proof boxes. They were all then stored in improved yam barns for four months after curing in February. Sprouts that developed on the non-irradiated tubers were broken off weekly. They were examined for rots and weight loss over the storage period. Sensory evaluation was conducted on the tubers at the end of storage to determine whether the treatments affected their sensory quality. It was observed that the irradiation and chemical insecticide treatments did not have significant effect (p>0.05) on percent rots and weight loss while the effect of storage on these parameters was significant (P