Cowpea Aphid Research Articles

Studies on the Detection of Viruses Infecting Capsicum Species in the Northern Zone of Cross River State, Nigeria

The objective of this study was to determine the occurrence, detection, and geographical spread of viruses that infect pepper (Capsicum spp.) in six towns spanning two local government areas (Yala and Ogoja) in the northern zone of Cross River State. A total of 348 leaf samples from symptomatic and asymptomatic pepper plants were randomly collected from farmer's fields during a survey in 2023–2024. The samples were then preliminary tested using an antigen coated plate enzyme-linked immunosorbent assay (ACP-ELISA) with seven antibodies specific for ToLCV, Cowpea aphid borne mosaic virus (CABMV), Cucumber mosaic virus (CMV), Potato virus X (PVX), Tobacco mosaic virus (TMV), and Pepper veinal mottle virus (PVMV). The findings showed that the viruses that infect pepper in Yala had a high cumulative mean incidence, accounting for 56.9% (198 infected samples). Yache in Yala had the highest virus incidence at 90%, while Bansara in Ogoja had the lowest at 40%. At different rates, ToLCV, CMV, PVY, and PVMV were found in the samples; PVX, TMV, and CABMV were not found. The CMV virus was the most commonly discovered of them. Additionally, mixed infections between the viruses—between ToLCV and PVY in Yache and between CMV and PVMV in Bansara—were found. This is the first report on account of viruses found in pepper in the northern part of Cross River State. The findings show that the viruses that cause the infections are common and might potentially be a threat to the production of pepper in that region.

Differential regulation of glucosinolate-myrosinase mediated defense determines host-aphid interaction in Indian mustard Brassica juncea L.

India's oilseed economy falls short of self-sufficiency and is supplemented by huge imports every year. Increasing national productivity of the major oilseeds is confronted with yield losses due to diverse biotic and abiotic stresses. The productivity of Indian mustard (Brassica juncea Linnaeus), belonging to the family Brassicaceae, is significantly reduced due to damage caused by mustard aphids (Lipaphis erysimi Kaltenbach, Hemiptera: Aphididae). Rapid colonization by the nymphs makes it difficult to protect the crop through agrochemicals. Aphids release effector molecules to modulate the host-defence responses. Glucosinolates (GSLs) extensively found in Brassicaceae family, are hydrolysed by myrosinase into toxic compounds that deter herbivore insects. Here, we investigated the differential activation of the glucosinolate-myrosinase pathway in mustard manifesting susceptibility and resistance to different aphid species. Mustard plants were challenged by two different aphid species mustard aphid and cowpea aphid (Aphis craccivora Koch, Hemiptera: Aphididae) leading to complete host-susceptibility in one case and resistance in the other, respectively. Differential regulation of the GSL biosynthetic pathway and myrosinase activity was assessed by gene expression study and ultra-performance liquid chromatography quadrupole time-of-flight tandem mass spectrometry (UPLC- QToF-ESL-MS). Gene expression study identified selective transcriptional attenuation of the key GSL biosynthetic and myrosinase gene in mustard when challenged with mustard aphid. In contrary, the activation of GSL biosynthetic genes in conjunction with myrosinase at the transcriptional level was profound in mustard, when challenged with cowpea aphid. UPLC-MS analysis showed higher turnover in the hydrolysis of glucosinolates by myrosinase which led to concomitant generation of glucose as byproduct in response to cowpea aphid in mustard plants. GSL-myrosinase pathway is specifically attenuated by the successful aphid species in mustard and thus plays a pivotal role in determining the outcome of the B. juncea-aphid interaction. The results open up a new genetic modification strategy for developing resistance against aphids.

Biological Manifestation of Different Temperature Regimes and Certain Insecticides on Cheilomenes sexmaculata (Fab.) Preying on Cowpea Aphid, Aphis craccivora Koch

Background: Ladybird beetles are great bio-control agents and campodeiform grubs of these little predators are able to devour aphids in a voracious fashion. They feed on a wide array of aphid species most noticeably on the infamous black aphids or cowpea aphids Aphis craccivora (Koch). Methods: The growth and feeding potential of C. sexmaculata were studied in the laboratory of the Department of Entomology, Faculty of Agricultural Sciences (Institute of Agricultural Sciences), SOA Deemed to be University, Bhubaneswar, India at four different temperatures 20°C, 25°C, 30°C and 35°C during 2021-2022. Result: The life history parameters indicated that the duration of eggs, larvae, pupae, adult males and adult females was longest at 30°C and shortest at 20°C. Such variations were also observed in morphometry and feeding potential. The trend was 30°C greater than 25°C greater than 35°C greater than 20°C. In the case of feeding potential the trend was adult female greater than adult male greater than 4th instar greater than 3rd instar greater than 2nd instar greater than 1st instar across all temperatures. Adult females lived longer than males and thereby consumed more aphids than males. Maximum consumption was seen in case of adult female at 30°C which was 633±5.71 aphids and least feeding was seen at 20°C by 1st instar grub which was 8.9±0.56 aphids. The effect of insecticides in direct spray method indicated that dimethoate 30EC killed more ladybirds and clothianidin 50% WDG killed the least. This trend was strong across all temperatures and insect growth stages. The feed contamination method indicated that clothianidin 50% WDG, imidacloprid 17.8% SL and thiamethoxam 25% WG produced higher mortality rates than direct contamination method. All insecticides showed increased mortality up to 72 h and the mortality trend was 72 HAT greater than 48 HAT greater than 24 HAT. The mortality rate of immature individuals is higher than that of adults.

Predation Efficiency and Biological Control Potential of Micromus angulatus Against Aphis craccivora

Micromus angulatus (Neuroptera: Hemerobiidae) is a widely distributed and highly effective predator that shows promise as a biological control agent against agricultural pests, particularly Aphis craccivora, the cowpea aphid, which threatens leguminous crops globally. This study aimed to evaluate the predation behaviour, search efficiency, and intraspecific interference of M. angulatus at different developmental stages, including first- to third-instar larvae and adults, in controlling adult A. craccivora populations. The results demonstrated that all developmental stages of M. angulatus exhibited predatory behaviour towards adult aphids, with the functional response fitting the Holling Type II model. The instantaneous attack rates for first-, second-, and third-instar larvae and adults were 1.0017, 1.0448, 0.9581, and 0.9508, respectively; the handling times were 0.0158, 0.0051, 0.0016, and 0.0011 days, respectively; and the theoretical maximum daily predation rates were 63.2911, 196.0784, 625, and 909.0909 aphids, respectively. The pest control efficacies were 63.3989, 204.8672, 598.8311, and 864.3192, respectively. The search efficiency at each developmental stage was negatively correlated with aphid density, which decreased as the prey density increased, with second-instar larvae showing the greatest decrease and adults the least. When the aphid density was fixed, the daily predation rate of individual M. angulatus decreased with increasing conspecific density, indicating that predation was affected by its own density, with the interference effect equation being E = 0.6194P−0.87. These findings indicate that M. angulatus, especially in the third-instar larval and adult stages, has considerable potential as a biological control agent for managing A. craccivora populations in agricultural settings. This study contributes valuable insights for developing sustainable agricultural practices by decreasing reliance on chemical pesticides.

Selection of Aphis craccivora (Hemiptera: Aphididae) for Resistance to Thiamethoxam Insecticide under Laboratory Conditions1

Abstract The cowpea aphid, Aphis craccivora Koch (Hemiptera: Aphididae), is a polyphagous pest that causes yield losses in a variety of crops worldwide. Its management relies mainly on the use of chemical insecticides. This study followed the development of resistance to thiamethoxam in A. craccivora under laboratory conditions for 24 generations. The initial median lethal concentration (LC50) of thiamethoxam in a susceptible laboratory population of A. craccivora was 2.62 ppm. Exposure of surviving aphids in each generation to thiamethoxam caused an increase in the LC50 with each successive generation. After 24 generations, the LC50 had increased to 225.83 ppm, an 86.2-fold increase over the initial LC50. Resistance, as indicated by the increasing LC50, appeared as early as the second generation with a 1.4-fold increase over the initial generation. By the 14th generation, the LC50 had increased by 29-fold, and by the 16th generation, it had quickly increased by 69.4-fold. Our results indicate that A. craccivora populations repeatedly exposed to thiamethoxam in a cropping system can lead to rapid development of resistance to the insecticide. Any overuse or other misuse of the pesticide may lead to an even more rapid development of high levels of resistance to thiamethoxam within a short period of time. Elevated levels of the detoxifying enzymes, carboxylesterase, glutathione-S-transferase, and mixed function oxidases, in aphids exhibiting resistance as compared with the initial susceptible population indicated that the detoxifying enzymes, especially the carboxylesterases, are likely involved in facilitating the development of resistance to thiamethoxam in A. craccivora.

Realized heritability and fitness costs of flupyradifurone resistance in the cowpea aphid, Aphis craccivora Koch

The cowpea aphid, Aphis craccivora Koch (Homoptera: Aphididae) is a serious insect pest that infests legume crops. Flupyradifurone (FPF) is a butenolide insecticide that selectively targets sucking insects including aphids and whiteflies. However, the realized heritability (h2) and fitness costs associated with resistance to FPF have not yet been assessed with A. craccivora. In this study, A. craccivora showed the potential to develop resistance to FPF under continuous selection, with an overall mean estimated h2 of resistance of 0.21. Results of fitness costs showed no differences in the developmental time (except for N2 and N3), longevity, fecundity, adult pre-reproductive period (APRP), total pre-reproductive period (TPRP), and oviposition days (Od) of the FPF-R strain compared to the S-strain. In contrast, all population growth parameters, including the growth reproductive rate (GRR), net reproductive rate (R0), intrinsic rate of increase (r), finite rate of increase (λ), mean generation time (T), and doubling time (DT), were significantly lower in the FPF-R strain than in the S-strain. Fitness cost studies revealed that resistance to FPF decreased the relative fitness of the FPF-R strain to 0.76 compared with that of the S-strain. The estimation of realized heritable h2 and identification of resistance fitness costs provide a basis for designing insecticide resistance management (IRM) programs to sustain susceptibility in insect populations.

Screening of Cowpea Germplasm against Cowpea Aphid (Aphis craccivora Koch, 1854) under Artificial Conditions

Screening of Cowpea Germplasm against Cowpea Aphid (Aphis craccivora Koch, 1854) under Artificial Conditions

Pyramiding aphid resistance genes into the elite cowpea variety, Zaayura, using marker-assisted backcrossing

The cowpea aphid (Aphis cracivora) is a cosmopolitan insect pest that causes economic damage on cowpea. Although the pest persists at all the growth stages of the crop, in West Africa, aphids are the only major insect pests that farmers regularly control at the vegetative stage. Thus, deploying aphid-resistant crop varieties can reduce farmers' expenditure on insecticide. The availability of different biotypes of the pest and reports of resistance breakdown necessitates pyramiding of sources of aphid resistance to develop a more robust genotype for durable resistance. Two aphid-resistance genes, sourced from SARC-1-57-2 and IT97K-556-6, were introgressed through gene pyramiding technique into a farmers’ preferred cowpea variety, Zaayura, using marker-assisted backcrossing. A simple sequence repeat (SSR) marker, CP 171F/172R, and an allele-specific single nucleotide polymorphism (SNP) marker, 1_0912, were used for foreground selection of the SARC-1-57-2 and IT97K-556-6 aphid resistance genes, respectively. A stepwise backcross approach was used to introgress the major aphid resistance QTL (QAc-vu7.1) from IT97K-556-6 into Zaayura using the marker 1_0912 coupled with intermittent screening under artificial aphid infestation. After the fourth backcross generation, three heterozygous BC4F1 of Zaayura/TT97K-556-6 were intercrossed to Zaayura Pali to develop intercross F1 (ICF1). Three true ICF1 hybrids allowed to self to produce ICF2. Five (5) out of 48 ICF2 plants which were genotyped with the two foreground markers had the two aphid resistance genes fixed in the double homozygous dominant state. For background selection, out of 192 allele-specific markers screened, only 47 polymorphic markers were identified and used for the background analysis of the pyramided lines. The recurrent parent genome recovery ranged from 72 to 93.8 %. ICF2_Zaa/556/SARC-P6 had the highest recurrent parent genome and the least heterozygosity among the five improved lines. The five pyramided lines showed superior resistance under artificial aphid infestation as compared to the two donor parents with damage scores ranging from 2.0 to 2.3. On the field, however, there were no significant differences between the pyramided lines and their recurrent parent for all the agronomic traits measured except for grain yield. The pyramided lines do not only stand the chance of being released as new varieties but are also valuable genetic resources for other breeding programs that seek to improve cowpea for aphid resistance.

Isolation and Characterization of Native Entomopathogenic Fungi and Their Pathogenicity Against The Cowpea aphid

Isolation and Characterization of Native Entomopathogenic Fungi and Their Pathogenicity Against The Cowpea aphid

Insecticidal activity of essential oils and plant extracts on cowpea aphid

Aphid population’s reduction occurs through chemical management, but the indiscriminate use of these products can cause environmental impacts and health risks. This study aimed to determine the insecticidal effects of essential oils and plant extracts as an alternative for aphid control management. The experimental design was entirely randomised in a 5x5 factorial scheme with five replications. Essential oils of rosemary, citronella, corn mint, and hydroethanolic extracts of garlic and cinnamon at five concentrations (0, 10, 20, 40, 80 μL.L−1) were used. In the exposure period of 96 h, the cinnamon hydroethanolic extract and the essential oil of corn mint (Mentha arvensis) showed a greater effect on aphid mortality. The other products evaluated showed lower mortalities but with the potential to be effective with dosages above 80 μL.L−1.

One-Pot, Four-Component Reaction for the Design, Synthesis, and SAR Studies of Novel Pyridines for Insecticidal Bioefficacy Screening against Cowpea Aphid (Aphis craccivora).

In this paper, novel pyridines 2-8 were designed and synthesized via the one-pot, four-component reaction of 2-formylphenyl 4-tolylsulfonate with malononitrile, ammonium acetate, and phenols or 2-thioxo-1,3-thiazolidin-4-one or 6-aminopyrimidine-2,4(1H,3H)-dione under microwave irradiation in an aqueous solution of water and ethanol (1:1 ratio). The structures of new pyridines 2-8 were elucidated by elemental and spectral analyses such as IR, 1H NMR, and 13CNMR. This application has many advantages, such as having easy workup, eco-friendliness, reaction time being short (6-13 min), high production (94-98%), inexpensiveness, and avoiding the use of harmful solvents. Moreover, all compounds have been investigated as insecticidal agents against cowpea aphid (Aphis craccivora) insects, and the toxicity effect was studied, followed by the structure-activity relationship. From the LC50 values, it has been found that compounds 7 and 8 were excellent and promising insecticidal agents, with LC50 values of 0.05 and 0.09 ppm against nymphs and 0.93 and 1.01 ppm against adults of cowpea aphid. Furthermore, the obtained results indicated that compounds 2-8 can be applied as insecticidal agents for the control of cowpea aphids and to protect agricultural crops from this destructive pest, which effects crop production and causes major economic damage.

Green chemistry approach for rapid synthesis of indol-3-yl-4H-pyran derivatives, biological assessments, and toxicological activities against Cowpea aphid (Aphis craccivora)

From diverse or indole-3-carbaldehyde, certain unique indol-3-yl-4H-pyran derivatives were generated by condensing with different nucleophiles. IR, 1HNMR, and elemental studies have all confirmed their chemical structures. The green catalyst for the formation of indol-3-yl-4H-pyran derivatives is a zinc-linked amino acid complex [Zn(L-proline)2]. Furthermore, the environmental friendliness of this synthetic technique was investigated by assessing the reusability of the Zn(L-proline)2 complex over five consecutive cycles with no significant loss of catalytic activity. This novel process has showed substantial advantages in terms of safety, simplicity, stability, mild conditions, a short reaction time, excellent yields, and good purity without the use of organic solvents. The antibacterial properties of the compounds produced were investigated and discovered to be promising. To determine whether compounds are appropriate as possible insecticidal agents, the toxicological activity of the synthesized compounds against Cowpea aphid, Aphis craccivora, was tested using leaf dip bioassay technique toxicity studies performed in the laboratory. KEY WORDS: One pot synthesis, Zn(L-proline)2, Indole-3-carbaldehyde, Aqueous media, Microwave irradiation, Cowpea aphid, toxicological activity Bull. Chem. Soc. Ethiop. 2024, 38(4), 1077-1090. DOI: https://dx.doi.org/10.4314/bcse.v38i4.21

Discovery and properties of novel analogues of the aphid pheromones nepetalactone and nepetalactol.

Pheromones have unique advantages for pest control. Current aphid pheromone research focuses on alarm and sex pheromones. However, practical applications are limited so far, as (E)-β-farnesene has only been investigated to a small extent as an alarm pheromone and only male aphids are targeted by sex pheromones. Previous literature reports electrophysiological responses and repellent behavior of asexual aphids to nepetalactone (1B), therefore our objective was to modify nepetalactone's structure to identify key fragments responsible for repellent effects, as guidance for subsequent modifications and further investigation. In this study, seven derivatives were designed and synthesized based on nepetalactol (1A) and nepetalactone (1B) as lead compounds. Free-choice tests, conducted using cowpea aphids (Aphis craccivora), revealed that the lactone moiety was crucial for the repellent activity, and the removal of the carbonyl group eliminated the repelling effect. Compound (±)1I, an analogue of nepetalactone (1B), demonstrated a significantly higher repellent value than nepetalactone (1B) at three different concentrations, and even at 0.1 mg/mL it maintained a considerable repellent effect (26.5%). Electrostatic potential and density functional theory calculations supported the importance of the carbonyl group for the repellent effects. The newly discovered para-pheromone (±)1I shows improved repellent effects and potential for development as a novel biological control agent. Based on our innovative findings, analogues with improved efficacy and properties can be designed and prepared. Our research contributes to understanding the effects of structural modifications on pheromone activity and properties, which is crucial for exploring novel pheromone-based products for crop protection. © 2024 Society of Chemical Industry.

Proteomic Analysis of Cowpea Aphid <i>Aphis craccivora</i> Koch Salivary Gland Using LC-MS/MS Analysis

The present study identified 151 proteins from the salivary gland of cowpea aphid Aphis craccivora Koch, using LC-MS/MS analysis. These included enzymes mainly involved in the digestion and detoxification of secondary metabolites and proteins related to cell development and molecular function. Enzymes like peroxidase, trehalase, cytochrome P450 monooxygenase, glutathione peroxidase, esterase, peptidase, carboxypeptidase, maltase, and beta-galactosidase were prevalent in the proteome. Additionally, several proteins were assigned to cellular and molecular functions of salivary gland. These proteins may be involved in host-plant interactions. Comprehensively, these results provide a database for elucidating aphid-plant interactions at the molecular level in the future.

Genetics, genomics, and breeding of black gram [Vigna mungo (L.) Hepper

Black gram [Vigna mungo (L.) Hepper] is a highly nutritious grain legume crop, mainly grown in South and Southeast Asia, with the largest area in India, where the crop is challenged by several biotic and abiotic stresses leading to significant yield losses. Improving genetic gains to increase on-farm yields is the primary goal of black gram breeding programs. This could be achieved by developing varieties resistant to major diseases like mungbean yellow mosaic disease, urdbean leaf crinkle virus, Cercospora leaf spot, anthracnose, powdery mildew, and insect pests such as whitefly, cowpea aphids, thrips, stem flies, and bruchids. Along with increasing on-farm yields, incorporating market-preferred traits ensures the adoption of improved varieties. Black gram breeding programs rely upon a limited number of parental lines, leading to a narrow genetic base of the developed varieties. For accelerating genetic gain, there is an urgent need to include more diverse genetic material for improving traits for better adaptability and stress resistance in breeding populations. The present review summarizes the importance of black gram, the major biotic and abiotic stresses, available genetic and genomic resources, major traits for potential crop improvement, their inheritance, and the breeding approaches being used in black gram for the development of new varieties.

Preliminary Evaluation of Onion Bulb and Tobacco Leaf Extracts for Insect Control and Yield of Cowpea in the Southern Guinea Savanna of Nigeria

The study evaluated the effects of onion (Allium cepa) bulb and tobacco (Nicotiana tabacum) leaf extract on the insect pests and yield components of cowpea. The extracts were tested on number of the flower thrips, Megalurothrips sjostedti Trybom, the pod-sucking bug, Clavigralla tomentosicollis Stal, the pod borer, Maruca vitrata (F.) and cowpea aphid, Aphis craccivora Koch. Also evaluated were the dry seed weight, 100-seed weight, pod length, number of pods per plant, number of seeds per pod, pod load, pod damage and pod evaluation index. Field experiment was conducted in the Faculty of Agriculture, University of Ilorin, Ilorin, Nigeria. Plots were laid out in a randomized complete block design with three replications. Treatments included 10% (w/v) of each of onion bulb and tobacco leaf extracts, synthetic insecticide (Cypermethrin 1 L/ha) and untreated control. Results revealed that cowpea treated with the plant extracts had significantly (p<0.05) lower insect pest population than plants in untreated plots which suffered greater insect pest attack. However, plots treated with Cypermethrin produced significantly higher number of seeds per pod than other treatments. Nevertheless, tobacco leaf extract produced significantly (p<0.05) heavier 100-seed weight than other treatments including the control. It could be concluded that the plant extracts had potential to replace the synthetic insecticide for control of insect pests of cowpea, thus ensuring environmental safety.

Bioactivity of aqueous extracts of annonaceous from the amazon savannah of Roraima on the cowpea aphid

Aphis craccivora Koch (Hemiptera: Aphididae), known as the cowpea aphid, is a polyphagous pest that causes severe damage throughout the phenological cycle of several economically important crops. For the control of this hemiptera, as for most agricultural pests, the chemical method has been the most used. Considering the Integrated Pest Management - IPM, the use of plant extracts is an option that has been widely considered. Thus, this study aimed to evaluate the bioactivity of aqueous extracts of Annona glabra, A. hypoglauca, A. montana and A. squamosa leaves, obtained in the Amazonian Savanna of Roraima, Brazil, on A. craccivora under laboratory conditions. Regarding the biological aspects on the cowpea aphid, the toxicity and repellency were evaluated with and without chance of choice. It was verified that the aqueous extracts of the four species of the genus Annona cause mortality in both nymphal and adult stages of A. craccivora, besides presenting repellent effect for this aphid. Because the aqueous extracts of leaves of the studied species present promising effects against A. craccivora, additional field studies of bioactivity of these Annona species on the black aphid, as well as their activity on beneficial and non-target organisms are suggested.

Identification of salivary proteins of the cowpea aphid Aphis craccivora by transcriptome and LC-MS/MS analyses

Aphid salivary proteins mediate the interaction between aphids and their host plants. Moreover, these proteins facilitate digestion, detoxification of secondary metabolites, as well as activation and suppression of plant defenses. The cowpea aphid, Aphis craccivora, is an important sucking pest of leguminous crops worldwide. Although aphid saliva plays an important role in aphid plant interactions, knowledge of the cowpea aphid salivary proteins is limited. In this study, we performed transcriptomic and LC-MS/MS analyses to identify the proteins present in the salivary glands and saliva of A. craccivora. A total of 1,08,275 assembled transcripts were identified in the salivary glands of aphids. Of all these assembled transcripts, 53,714 (49.11%) and 53,577 (49.48%) transcripts showed high similarity to known proteins in the Nr and UniProt databases, respectively. A total of 2159 proteins were predicted as secretory proteins from the salivary gland transcriptome dataset, which contain digestive enzymes, detoxification enzymes, previously known effectors and elicitors, and potential proteins whose functions have yet to be determined. The proteomic analysis of aphid saliva resulted in the identification of 171 proteins. Tissue-specific expression of selected genes using RT-PCR showed that three genes were expressed only in the salivary glands. Overall, our results provide a comprehensive repertoire of cowpea aphid salivary proteins from the salivary gland and saliva, which will be a good resource for future effector functional studies and might also be useful for sustainable aphid management.

Potency of emulsifiable concentrate and nanoemulsion formulations as green insecticides against two insects, Aphis craccivora and Liriomyza trifolii

The current research aims to develop emulsifiable concentrates (EC) and nanoemulsions derived from the plant essential oils of Salvia officinalis (L.) and Melissa officinalis (L.) at a concentration of 5%. The toxicity of the prepared formulations was evaluated against two insect species, the cowpea aphid, Aphis craccivora (Koch), and the broad bean leafminer, Liriomyza trifolii (Burgess). EC preparations were formed by mixing the essential oils with Tween 80, vegetable, and mineral oils. The nanoemulsions were manufactured by mixing different ratios of the essential oils and the surfactant (Tween 80) into an aqueous solution, followed by an ultrasonic emulsification process. The results showed that both EC and nanoemulsions with a ratio of essential oil to Tween 80 of 1:2 after 10 min of sonication passed the physical characteristics. The particle droplet size, zeta potential, and transmission electron microscopy (TEM) were measured for the successful nanoemulsion formulations. The ultrasonication and stirring procedures lowered the amounts of essential oils during preparations of S. officinalis and M. officinalis nanoemulsions to 17% and 20%, respectively. The laboratory trials elucidated that EC formulations were more potent than nanoemulsions for two insect species after a short period of time. While the field experiments showed that nano-formulations were more efficient than EC formulations with time elapsing. The results suggested that the prepared nanoemulsions can be used as eco-friendly alternatives to synthetic insecticides for controlling A. craccivora and L. trifolii infestations.

Bioefficacy of engineered Beauveria bassiana with scorpion neurotoxin, LqqIT1 against cotton mealybug, Phenacoccus solenopsis and cowpea aphid, Aphis craccivora.

Cotton mealybug, Phenacoccus solenopsis (Tinsley) and cowpea aphid Aphis craccivora (Koch) are notorious polyphagous, hemipteran sap sucking insect pests. A recombinant toxin gene 'LqqIT1' from the scorpion Leiurus quinquestriatus quinquestriatus (Ehrenberg) was cloned in the pAL1 fungal expression vector and then expressed in the entomopathogenic fungus Beauveria bassiana (Balasmo) using genetic modification techniques. The genetically transformed B. bassiana strain (BbLqqIT1-3) and its un-transformed parent strain (Bb-C) were screened to infect the third instar nymphs of P. solenopsis and first instar nymph of A. craccivora through leaf treatment and topical application (spray) method at 1 * 107 spores per ml concentration. The recombinant strain BbLqqIT1-3 was highly pathogenic against A. craccivora but non pathogenic to P. solenopsis. BbLqqIT1-3 induced 72 and 43.33% mortality in A. craccivora nymphs 96 h after leaf treatment and topical application, respectively. The nymphs of A. craccivora infected with BbLqqIT1-3 displayed classical neurotoxic symptoms such as sluggishness, solublize and liquification of the body. Crude soluble toxin protein, BbLqqIT1a-CSE and Bb-WT-CSE was extracted from the BbLqqIT1-3 and Bb-C, respectively using ammonium sulphate precipitation method, and their oral toxicity was analyzed at 5 µg/ml concentration. The survival of the studied insects was negatively affected by the crude soluble toxin extracts. The LT50 values of BbLqqIT1a-CSE against P. solenopsis and A. craccivora were 22.18 and 17.69 h, respectively. Exposure to crude soluble toxin extracts also accounted for the imbalance of ionic concentrations in the hemolymph of treated insects such as hyperpotassemia (3.53-8.18 meq/ml) in the P. solenopsis and hypopotassemia (7.52-0.47 meq/ml) in A. craccivora. The transformed fungus BbLqqIT1-3 strain exhibited promising results in invitro study.