Sap-sucking Insect Pests Research Articles

The tiered-evaluation of the effects of transgenic cry1c rice on Cyrtorhinus lividipennis, a main predator of Nilaparvata lugens

T1C-19, a newly developed transgenic cry1C rice line, expresses cry1C under the control of the maize ubiquitin promoter, and is highly resistant to lepidopteran pests of rice. Cyrtorhinus lividipennis is the major predator of the eggs and young nymphs of Nilaparvata lugens, which is the main non-target sap-sucking insect pest of Bt rice. C. lividipennis may be exposed to Cry1C protein, thus biosafety evaluations of transgenic cry1C rice on C. lividipennis should be conducted before the commercialization of T1C-19. In the current study, we tested the direct toxicity of elevated doses of Cry1C to C. lividipennis, effects of T1C-19 on the life-table parameters of C. lividipennis via preying planthoppers, and effects of T1C-19 on the population density and dynamics in rice fields. No detrimental effects on development, survival, female ratio and body weight of C. lividipennis were caused by direct exposure to elevated doses of the Cry1C protein or prey-mediated exposure to realistic doses of the protein. The population density and dynamics did not significantly differ between C. lividipennis in T1C-19 and non-transgenic rice fields. Thus, transgenic cry1C rice had no negative effects on C. lividipennis. This is the first report of the effects of transgenic cry1C rice on C. lividipennis.

Map-based Cloning and Characterization of the BPH18 Gene from Wild Rice Conferring Resistance to Brown Planthopper (BPH) Insect Pest.

Brown planthopper (BPH) is a phloem sap-sucking insect pest of rice which causes severe yield loss. We cloned the BPH18 gene from the BPH-resistant introgression line derived from the wild rice species Oryza australiensis. Map-based cloning and complementation test revealed that the BPH18 encodes CC-NBS-NBS-LRR protein. BPH18 has two NBS domains, unlike the typical NBS-LRR proteins. The BPH18 promoter::GUS transgenic plants exhibited strong GUS expression in the vascular bundles of the leaf sheath, especially in phloem cells where the BPH attacks. The BPH18 proteins were widely localized to the endo-membranes in a cell, including the endoplasmic reticulum, Golgi apparatus, trans-Golgi network, and prevacuolar compartments, suggesting that BPH18 may recognize the BPH invasion at endo-membranes in phloem cells. Whole genome sequencing of the near-isogenic lines (NILs), NIL-BPH18 and NIL-BPH26, revealed that BPH18 located at the same locus of BPH26. However, these two genes have remarkable sequence differences and the independent NILs showed differential BPH resistance with different expression patterns of plant defense-related genes, indicating that BPH18 and BPH26 are functionally different alleles. These findings would facilitate elucidation of the molecular mechanism of BPH resistance and the identified novel alleles to fast track breeding BPH resistant rice cultivars.

Screening and Functional Analyses of Nilaparvata lugens Salivary Proteome.

Most phloem-feeding insects secrete gelling and watery saliva during the feeding process. However, the functions of salivary proteins are poorly understood. In this study, our purpose was to reveal the components and functions of saliva in a rice sap-sucking insect pest, Nilaparvata lugens. The accomplishment of the whole genome and transcriptome sequencing in N. lugens would be helpful for elucidating the gene information and expression specificity of the salivary proteins. In this study, we have, for the first time, identified the abundant protein components from gelling and watery saliva in a monophagous sap-sucking insect species through shotgun proteomic detection combined with the genomic and transcriptomic analysis. Eight unknown secreted proteins were limited to N. lugens, indicating species-specific saliva components. A group of annexin-like proteins first identified in the secreted saliva displayed different domain structure and expression specificity with typical insect annexins. Nineteen genes encoding five annexin-like proteins, six salivaps (salivary glands-specific proteins with unknown function), seven putative enzymes, and a mucin-like protein showed salivary gland-specific expression pattern, suggesting their importance in the physiological mechanisms of salivary gland and saliva in this insect species. RNA interference revealed that salivap-3 is a key protein factor in forming the salivary sheath, while annexin-like5 and carbonic anhydrase are indispensable for N. lugens survival. These novel findings will greatly help to clarify the detailed functions of salivary proteins in the physiological process of N. lugens and elucidate the interaction mechanisms between N. lugens and the rice plant, which could provide important targets for the future management of rice pests.

Double-Stranded RNA-Mediated Silencing of Sodium Channel and Ultraspiracle Genes inAphis gossypii(Hemiptera: Aphididae)

Overuse of chemical insecticides such as organophosphates, pyrethroids, and endosulfan in managing notorious sap-sucking insect pests such as the melon aphid, Aphis gossypii Glover, resulted in insecticide resistance. To combat the above and bring out the novel pest control strategy, we implemented ribonucleic acid interference (RNAi), a reverse genetics tool in silencing the target genes. RNAi is a sequence-specific gene-silencing mechanism triggered by double-stranded ribonucleic acid (dsRNA). The efficiency of RNAi is reliant upon concentration of dsRNA, mode of delivery, gene targets, insect species, etc. The objective of the present study was to assess the extent of down-regulation by using two different concentrations of dsRNA specific to sodium channel ( AgSCN ) and ultraspiracle genes ( AgUSP ) (0.0625 and 0.125 µg/µl) with two time intervals (48 and 96 h) through oral delivery. The extent of declined gene expression and percentage mortality chronicled for sodium channel and USP is proportional to the dsRNA concentration. Thus, our study affirms the outlook in the development of RNAi which can form a potent species-specific tool in the management of insect pests such as A. gossypii .

Ethylene Contributes to maize insect resistance1-Mediated Maize Defense against the Phloem Sap-Sucking Corn Leaf Aphid.

Signaling networks among multiple phytohormones fine-tune plant defense responses to insect herbivore attack. Previously, it was reported that the synergistic combination of ethylene (ET) and jasmonic acid (JA) was required for accumulation of the maize insect resistance1 (mir1) gene product, a cysteine (Cys) proteinase that is a key defensive protein against chewing insect pests in maize (Zea mays). However, this study suggests that mir1-mediated resistance to corn leaf aphid (CLA; Rhopalosiphum maidis), a phloem sap-sucking insect pest, is independent of JA but regulated by the ET-signaling pathway. Feeding by CLA triggers the rapid accumulation of mir1 transcripts in the resistant maize genotype, Mp708. Furthermore, Mp708 provided elevated levels of antibiosis (limits aphid population)- and antixenosis (deters aphid settling)-mediated resistance to CLA compared with B73 and Tx601 maize susceptible inbred lines. Synthetic diet aphid feeding trial bioassays with recombinant Mir1-Cys Protease demonstrates that Mir1-Cys Protease provides direct toxicity to CLA. Furthermore, foliar feeding by CLA rapidly sends defensive signal(s) to the roots that trigger belowground accumulation of the mir1, signifying a potential role of long-distance signaling in maize defense against the phloem-feeding insects. Collectively, our data indicate that ET-regulated mir1 transcript accumulation, uncoupled from JA, contributed to heightened resistance to CLA in maize. In addition, our results underscore the significance of ET acting as a central node in regulating mir1 expression to different feeding guilds of insect herbivores.

Development and feeding effect of frosted scaleParthenolecanium pruinosum Cocquillet (Hemiptera: Coccidae) on selectedVitis vinifera L. cultivars

Background and Aims Frosted scale is a sap-sucking insect pest that feeds on several commercial Vitis vinifera cultivars across several wine regions of Australia. The ability to develop and the impact of its feeding activity on grapevines have not been documented. We have closed this knowledge gap through a study that examined the development and feeding effect of frosted scale on Pinot Noir, Riesling and Sauvignon Blanc. Methods and Results A replicated glasshouse experiment was established by allocating the potted rootlings of the three cultivars into two treatment regimes, control (uninfested) and treated (infested with frosted scale) grapevines in the summer months between November 2011 and March 2012. Frosted scale population was relatively high on Riesling, moderate on Pinot Noir and least on Sauvignon Blanc. The presence of frosted scale significantly reduced leaf chlorophyll concentration and the number of internodes per vine. An increasing number of scales did not significantly affect the chlorophyll concentration in any cultivar. An increasing number of scales did significantly decrease the number of internodes per vine. The proportion of dropped leaves in all cultivars exposed to frosted scale was higher than that of control plants. Riesling dropped more leaves than Pinot Noir or Sauvignon Blanc. Conclusions An increase in first and second instar populations of frosted scale feeding mainly on grapevine leaves was observed. This feeding may reduce leaf chlorophyll and the number of internodes per vine. Pinot Noir, Riesling and Sauvignon Blanc were all susceptible to frosted scale feeding under glasshouse conditions, but individual cultivar performance varied. Significance of the Study Grapegrowers could expect frosted scale population and loss of vine vigour to increase on highly susceptible cultivars, such as Riesling. Further studies regarding cultivar differences in response to frosted scale feeding are necessary to clarify these results.

Temperature and Development Impacts on Housekeeping Gene Expression in Cowpea Aphid, Aphis craccivora (Hemiptera: Aphidiae).

Quantitative real-time PCR (qRT-PCR) is a powerful technique to quantify gene expression. To standardize gene expression studies and obtain more accurate qRT-PCR analysis, normalization relative to consistently expressed housekeeping genes (HKGs) is required. In this study, ten candidate HKGs including elongation factor 1 α (EF1A), ribosomal protein L11 (RPL11), ribosomal protein L14 (RPL14), ribosomal protein S8 (RPS8), ribosomal protein S23 (RPS23), NADH-ubiquinone oxidoreductase (NADH), vacuolar-type H+-ATPase (ATPase), heat shock protein 70 (HSP70), 18S ribosomal RNA (18S), and 12S ribosomal RNA (12S) from the cowpea aphid, Aphis craccivora Koch were selected. Four algorithms, geNorm, Normfinder, BestKeeper, and the ΔCt method were employed to evaluate the expression profiles of these HKGs as endogenous controls across different developmental stages and temperature regimes. Based on RefFinder, which integrates all four analytical algorithms to compare and rank the candidate HKGs, RPS8, RPL14, and RPL11 were the three most stable HKGs across different developmental stages and temperature conditions. This study is the first step to establish a standardized qRT-PCR analysis in A. craccivora following the MIQE guideline. Results from this study lay a foundation for the genomics and functional genomics research in this sap-sucking insect pest with substantial economic impact.

A Comprehensive Selection of Reference Genes for RT-qPCR Analysis in a Predatory Lady Beetle, Hippodamia convergens (Coleoptera: Coccinellidae).

Reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) is a reliable, rapid, and reproducible technique for measuring and evaluating changes in gene expression. To facilitate gene expression studies and obtain more accurate RT-qPCR data, normalization relative to stable reference genes is required. In this study, expression profiles of seven candidate reference genes, including β-actin (Actin), elongation factor 1 α (EF1A), glyceralde hyde-3-phosphate dehydro-genase (GAPDH), cyclophilins A (CypA), vacuolar-type H+-ATPase (ATPase), 28S ribosomal RNA (28S), and 18S ribosomal RNA (18S) from Hippodamia convergens were investigated. H. convergens is an abundant predatory species in the New World, and has been widely used as a biological control agent against sap-sucking insect pests, primarily aphids. A total of four analytical methods, geNorm, Normfinder, BestKeeper, and the ΔCt method, were employed to evaluate the performance of these seven genes as endogenous controls under diverse experimental conditions. Additionally, RefFinder, a comprehensive evaluation platform integrating the four above mentioned algorithms, ranked the overall stability of these candidate genes. A suite of reference genes were specifically recommended for each experimental condition. Among them, 28S, EF1A, and CypA were the best reference genes across different development stages; GAPDH, 28S, and CypA were most stable in different tissues. GAPDH and CypA were most stable in female and male adults and photoperiod conditions, 28S and EF1A were most stable under a range of temperatures, Actin and CypA were most stable under dietary RNAi condition. This work establishes a standardized RT-qPCR analysis in H. convergens. Additionally, this study lays a foundation for functional genomics research in H. convergens and sheds light on the ecological risk assessment of RNAi-based biopesticides on this non-target biological control agent.

Fine mapping of GRH3 conferring resistance to green rice leafhopper in rice (Oryza sativa L.)

Green rice leafhopper (GRH) is a major sap-sucking insect pest that causes large annual yield losses in rice by transmitting the rice dwarf virus or spreading sooty mold fungi. Genetic resistance is the most effective approach to control GRH as well as the spread of diseases. We performed a genetic analysis to detect the GRH resistant region in rice cv. ‘Cheongnam’ using bulk segregant analysis of the F2 population derived from a cross between GRH-resistant cv. ‘Cheongnam’ and GRH-susceptible cv. ‘Junam’. Two simple sequence repeat (SSR) markers, RM6818 and RM20142, demonstrated polymorphism between the parents, and between the resistant and susceptible bulks, and were located at the same region of GRH3 on chromosome 6. GRH3 was narrowed down to an interval between the RM20132 and RM20152 SSR markers, covering a 435-kb region of the ‘Nipponbare’ genome. We tested 1,000 individuals of the F2 population and 20 germplasm accessions and determined that GRH resistance co-segregated with SSR markers RM20142 and RM20145, which reside within the 435-kb region. This result demonstrates that these closely linked SSR markers are a convenient tool for the selection of GRH-resistant lines and cultivars.

Molecular and insecticidal characterization of a novel Cry-related protein from Bacillus thuringiensis toxic against Myzus persicae.

This study describes the insecticidal activity of a novel Bacillus thuringiensis Cry-related protein with a deduced 799 amino acid sequence (~89 kDa) and ~19% pairwise identity to the 95-kDa-aphidicidal protein (sequence number 204) from patent US 8318900 and ~40% pairwise identity to the cancer cell killing Cry proteins (parasporins Cry41Ab1 and Cry41Aa1), respectively. This novel Cry-related protein contained the five conserved amino acid blocks and the three conserved domains commonly found in 3-domain Cry proteins. The protein exhibited toxic activity against the green peach aphid, Myzus persicae (Sulzer) (Homoptera: Aphididae) with the lowest mean lethal concentration (LC50 = 32.7 μg/mL) reported to date for a given Cry protein and this insect species, whereas it had no lethal toxicity against the Lepidoptera of the family Noctuidae Helicoverpa armigera (Hübner), Mamestra brassicae (L.), Spodoptera exigua (Hübner), S. frugiperda (J.E. Smith) and S. littoralis (Boisduval), at concentrations as high as ~3.5 μg/cm2. This novel Cry-related protein may become a promising environmentally friendly tool for the biological control of M. persicae and possibly also for other sap sucking insect pests.

Bt Rice Expressing Cry2Aa Does Not Harm Cyrtorhinus lividipennis, a Main Predator of the Nontarget Herbivore Nilapavarta lugens

T2A-1 is a newly developed transgenic rice that expresses a synthesized cry2Aa gene driven by the maize ubiquitin promoter. T2A-1 exhibits high resistance against lepidopteran pests of rice. The brown planthopper, Nilapavarta lugens (Stål), is a main nontarget sap-sucking insect pest of rice, and Cyrtorhinus lividipennis (Reuter) is the major predator of the eggs and young nymphs of planthoppers. As C. lividipennis may expose to the Cry2Aa protein via N. lugens, it is therefore essential to assess the potential effects of transgenic cry2Aa rice on this predator. In the present study, three experiments were conducted to evaluate the ecological risk of transgenic cry2Aa rice to C. lividipennis: (1) a direct feeding experiment in which C. lividipennis was fed an artificial diet containing Cry2Aa at the dose of 10-time higher than that it may encounter in the realistic field condition; (2) a tritrophic experiment in which the Cry2Aa protein was delivered to C. lividipennis indirectly through prey eggs or nymphs; (3) a realistic field experiment in which the population dynamics of C. lividipennis were investigated using vacuum-suction. Both direct exposure to elevated doses of the Cry2Aa protein and prey-mediated exposure to realistic doses of the protein did not result in significant detrimental effects on the development, survival, female ratio and body weight of C. lividipennis. No significant differences in population density and population dynamics were observed between C. lividipennis in transgenic cry2Aa and nontransgenic rice fields. It may be concluded that transgenic cry2Aa rice had no detrimental effects on C. lividipennis. This study represents the first report of an assessment continuum for the effects of transgenic cry2Aa rice on C. lividipennis.

Diversity and localization of bacterial endosymbionts from whitefly species collected in Brazil.

Whiteflies (Hemiptera: Aleyrodidae) are sap-sucking insect pests, and some cause serious damage in agricultural crops by direct feeding and by transmitting plant viruses. Whiteflies maintain close associations with bacterial endosymbionts that can significantly influence their biology. All whitefly species harbor a primary endosymbiont, and a diverse array of secondary endosymbionts. In this study, we surveyed 34 whitefly populations collected from the states of Sao Paulo, Bahia, Minas Gerais and Parana in Brazil, for species identification and for infection with secondary endosymbionts. Sequencing the mitochondrial Cytochrome Oxidase I gene revealed the existence of five whitefly species: The sweetpotato whitefly Bemisia tabaci B biotype (recently termed Middle East-Asia Minor 1 or MEAM1), the greenhouse whitefly Trialeurodes vaporariorum, B. tabaci A biotype (recently termed New World 2 or NW2) collected only from Euphorbia, the Acacia whitefly Tetraleurodes acaciae and Bemisia tuberculata both were detected only on cassava. Sequencing rRNA genes showed that Hamiltonella and Rickettsia were highly prevalent in all MEAM1 populations, while Cardinium was close to fixation in only three populations. Surprisingly, some MEAM1 individuals and one NW2 population were infected with Fritschea. Arsenopnohus was the only endosymbiont detected in T. vaporariorum. In T. acaciae and B. tuberculata populations collected from cassava, Wolbachia was fixed in B. tuberculata and was highly prevalent in T. acaciae. Interestingly, while B. tuberculata was additionally infected with Arsenophonus, T. acaciae was infected with Cardinium and Fritschea. Fluorescence in situ hybridization analysis on representative individuals showed that Hamiltonella, Arsenopnohus and Fritschea were localized inside the bacteriome, Cardinium and Wolbachia exhibited dual localization patterns inside and outside the bacteriome, and Rickettsia showed strict localization outside the bacteriome. This study is the first survey of whitely populations collected in Brazil, and provides further insights into the complexity of infection with secondary endosymionts in whiteflies.

Effect of entomopathogenic Aspergillus strains against the pea aphid, Acyrthosiphon pisum (Hemiptera: Aphididae)

Aphids (Homoptera: Aphididae) are sap-sucking insect pests that feed on several plants of agronomical importance. Entomopathogenic fungi are valuable tools for potential aphid control. As part of a selection process, laboratory bioassays were carried with five different concentrations of Aspergillus clavatus (Desmazieres), Aspergillus flavus (Link) and Metarhizium anisopliae ((Metschnikoff) Sorokin) spores against the pea aphid, Acyrthosiphon pisum (Harris). Aspergillus isolates induced higher mortalities than M. anisopliae, which is a well-known entomopathogen in the literature. Lethal concentrations (LC50 and LC90) were 1.23 × 103 and 1.34 × 107 spores/ml for A. flavus, 4.95 × 102 and 5.65 × 107 spores/ml for A. clavatus, and 3.67 × 103 and 9.71 × 107 spores/ml for M. anisopliae 5 days after treatment. Mycelia development and sporulation on adult cadavers were observed 48 h after incubation. The intrinsic growth rate of A. pisum decreased with increased spore concentration for all fungal strains, suggesting an increase in pathogen fitness related to a consumption of host resources. In conclusion, Aspergillus species could be useful in aphid control as pest control agents despite their saprophytic lifestyle. This is also to our knowledge the first report of A. clavatus and A. flavus strains pathogenic to aphids.

Development of Transgenic Rice Harbouring Mutated Rice 5-Enolpyruvylshikimate 3-Phosphate Synthase (Os-mEPSPS) and Allium sativum Leaf Agglutinin (ASAL) Genes Conferring Tolerance to Herbicides and Sap-Sucking Insects

Globally, weeds and sap-sucking insects are major constrains in rice production. We have combined two desired traits for resistance to glyphosate and sapsuckers by transgenic overexpression of mutated rice 5-enolpyruvylshikimate3-phosphate synthase (Os-mEPSPS) and garlic leaf lectin (Allium sativum leaf agglutinin, ASAL) in a high yielding IR-64 rice cultivar. Polymerase chain reaction (PCR), southern and genome walking analyses showed stable integration of transgenes in genomes of transgenic lines. The molecular analysis of transgenic lines revealed effective expression of both Os-mEPSPS and ASAL transcripts and their respective proteins and imparted resistance to glyphosate and brown planthopper. In planta brown hopper assays in the progenies of independent rice transgenic lines exhibit enhanced ASAL expression that imparts substantial level of resistance, reduced survival and fecundity of brown hoppers by ~74 and ~68 %, respectively. The glyphosate and sap-sucking insect pest-resistant transgenic rice lines showed normal phenotype and no growth penalty or fitness costs. The double transgenic traits co-segregated as a single unit in the subsequent generations. In spite of the presence of several herbicide- and insect-resistant GM rice crops in the market, there is a need to develop new transgenic rice lines by selecting the transgenes from homologous and/or edible crop sources that circumvent the biosafety issues raised by regulatory bodies regarding the acceptance of these products for human consumption. In this scenario, the transgenic rice varieties generated in this study serve as a novel genetic resource in rice breeding aimed at durable resistance to glyphosate and sap-sucking insect pests.

Phloem-specific expression of the lectin gene from Allium sativum confers resistance to the sap-sucker Nilaparvata lugens

Rice production is severely hampered by insect pests. Garlic lectin gene (ASAL) holds great promise in conferring protection against chewing (lepidopteran) and sap-sucking (homopteran) insect pests. We have developed transgenic rice lines resistant to sap-sucking brown hopper (Nilaparvata lugens) by ectopic expression of ASAL in their phloem tissues. Molecular analyses of T0 lines confirmed stable integration of transgene. T1 lines (NP 1-2, 4-3, 11-6 & 17-7) showed active transcription and translation of ASAL transgene. ELISA revealed ASAL expression was as high as 0.95% of total soluble protein. Insect bioassays on T2 homozygous lines (NP 18 & 32) revealed significant reduction (~74-83%) in survival rate, development and fecundity of brown hoppers in comparison to wild type. Transgenics exhibited enhanced resistance (1-2 score) against brown hoppers, minimal plant damage and no growth penalty or phenotypic abnormalities.

SiRNA Machinery in Whitefly (Bemisia tabaci)

BackgroundRNA interference has been emerged as an utmost tool for the control of sap sucking insect pests. Systemic response is necessary to control them in field condition. Whitefly is observed to be more prone to siRNA in recent studies, however the siRNA machinery and mechanism is not well established.Methodology/Principal FindingsTo identify the core siRNA machinery, we curated transcriptome data of whitefly from NCBI database. Partial mRNA sequences encoding Dicer2, R2D2, Argonaute2 and Sid1 were identified by tblastn search of homologous sequences from Aphis glycines and Tribolium castaneum. Complete encoding sequences were obtained by RACE, protein sequences derived by Expasy translate tool and confirmed by blastp analysis. Conserved domain search and Prosite-Scan showed similar domain architecture as reported in homologs from related insects. We found helicase, PAZ, RNaseIIIa, RNaseIIIb and double-stranded RNA-binding fold (DSRBF) in Dicer2; DsRBD in R2D2; and PAZ and PIWI domains in Argonaute2. Eleven transmembrane domains were detected in Sid1. Sequence homology and phylogenetic analysis revealed that RNAi machinery of whitefly is close to Aphids. Real-time PCR analysis showed similar expression of these genes in different developmental stages as reported in A. glycines and T. castaneum. Further, the expression level of above genes was quite similar to the housekeeping gene actin.Conclusions/SignificanceAvailability of core siRNA machinery including the Sid1 and their universal expression in reasonable quantity indicated significant response of whitefly towards siRNA. Present report opens the way for controlling whitefly, one of the most destructive crop insect pest.

Receptors of Garlic (Allium sativum) Lectins and Their Role in Insecticidal Action

Garlic (Allium sativum) lectins are promising candidate molecules for the protection against chewing (lepidopteran) as well as sap sucking (homopteran) insect pests. Molecular mechanism of toxicity and interaction of lectins with midgut receptor proteins has been described in many reports. Lectins show its effect right from sensory receptors of mouth parts by disrupting the membrane integrity and food detection ability. Subsequently, enter into the gut lumen and interact with midgut glycosylated proteins like alkaline phosphatase (ALP), aminopeptidase-N (APN), cadherin-like proteins, polycalins, sucrase, symbionin and others. These proteins play critical role in life cycle of insect directly or indirectly. Lectins interfere with the activity of these proteins and causes physiological disorders leading to the death of insects. Lectins further transported across the insect gut, accumulated in various body parts (like haemolymph and ovary) and interact with intracellular proteins like symbionin and cytochrome p450. Binding with cytochrome p450 (which involve in ecdysone synthesis) might interfere in the development of insects, which results in growth retardation and pre-mature death.

Repellence property of traditional plant leaf extracts against Aphis gossypii Glover and Phenacoccus solenopsis Tinsley

Aphid, Aphis gossypii Glover (Hemiptera: Aphididae) and mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) are major polyphagous pests in Vadodara agricultural fields. To control these sap sucking insect pests; farmers are using broad spectrum insecticides which are toxic to non target insects. Therefore, the objective of this study is to control these pests by using biorational control methods. Hence, laboratory assays were carried out to evaluate the repellent property of leaf extracts of three indigenous native botanicals namely; Azadirachta indica A. Juss; Eucalyptus globules L. and Ocimum basilicum L. against aphids and mealybugs. The methanol extract of leaf was isolated by using soxhlet method. The leaf extracts were applied against aphids and mealybugs at dose levels of 1, 2, 4, 8 and 10%. Observations were made at 12 and 24 h. After 24 h of release of aphids and mealybugs, the highest repellency was recorded in A. indica leaf extract which gives 99.0 and 97.0% followed by E. globules leaf extract giving 96.0 and 93.0%. While minimum repulsion was seen in O. basilicum leaf extract 91.0 and 88.0%, respectively. As the dose increases, the repellent effect also increased irrespective of the plant extracts. The use of such plant extracts can control the population of serious pests like aphids and mealybugs in an environmental friendly way. Key words: Aphid, mealybug, biorational control, botanicals, Azadirachta indica, Eucalyptus globules, Ocimum basilicum.

Exploring the Insecticidal Potentiality of <i>Amorphophallus paeonifolius</i> Tuber Agglutinin in Hemipteran Pest Management

Hemipteran group of sap sucking insect pests cause worldwide crop destruction. The role of mannose specific monocot lectins have recently been worked out in hemipteran pest management. The present article demonstrates the insecticidal efficacy of a new mannose specific agglutinin, isolated from tubers of Amorphophallus paeonifolius (AMTL) against a wide range of hemipteran insects. The 25 kDa dimeric protein was found to inhibit the survivability of hemipteran insects namely, Lipaphis erysimi, Aphis gossypii and Dysdercus cingulatus quite efficiently, as analysed by synthetic diet based bioassay experiments. Surface Plasmon Resonance study detected binding of insecticidal AMTL to insect gut brush border membrane vesicle (BBMV) protein, an absolute prerequisite for conferring toxicity against target insects. Further ligand blot analysis spotted a ~74 kDa glycoprotein as putative receptor of AMTL from the total BBMV protein fraction of Lipaphis erysimi. Phylogenetic analysis showed a significant relatedness of AMTL to the previously established monocot lectin Galanthus nivalis agglutinin (GNA) in terms of their conserved mannose binding domains, agglutinating ability of rabbit erythrocytes and insecticidal efficacies. These information project AMTL as a promising candidate in preventing crop loss caused due to hemipteran insect attack.

Efficacy of a Cladosporium sp. fungus against Helicoverpa armigera (Lepidoptera: Noctuidae), other insect pests and beneficial insects of cotton

A strain of the fungus Cladosporium sp. (RM16) from an egg of Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) was assessed as a potential biocontrol agent for this pest. Pathogenicity of the fungus was tested against H. armigera eggs and larvae, cotton aphids (Aphis gossypii Glover; Homoptera: Aphididae), and silverleaf whitefly type B (Bemisia tabaci Gennadius; Hemiptera: Aleyrodidae). The pathogenicity of the fungus to the predatory red and blue beetles (Dicranolaius bellulus Guérin-Méneville; Coleoptera: Melyridae), transverse ladybird beetles (Coccinella transversalis Fabricius; Coleoptera: Coccinellidae), green lacewings (Mallada signatus Schneider; Neuroptera: Chrysopidae) and damsel bugs (Nabis kinbergii Reuter; Hemiptera: Nabidae), was also assessed in the laboratory. Fungus treatment resulted in failure to hatch of up to 64% of H. armigera eggs (compared with 11% in the controls) and mortality of 54% of first instar H. armigera larvae (compared with 5% in the controls). In contrast, it was not pathogenic to later instar H. armigera larvae. Cladosporium RM16 was also efficacious against the sap-sucking insect pests of cotton that were tested. No significant harmful effect of the fungus was found on any of the four beneficial predatory insects assessed in this study. Cladosporium RM16 has the potential as biological control agent to support integrated pest management in cotton farming systems, although this needs intensive study.