Use Of Synthetic Chemical Pesticides Research Articles

Actinobacteria mediated synthesis of silver nanoparticles using Streptomyces diastaticus and their biological efficacy against human vector mosquitoes and agricultural insect pests.

Mosquitoes and agricultural insects were harmful to both public health and crops. Prolonged use of synthetic chemical pesticides for insect pest control was associated with resistance development and negative human and ecological effects. This study investigates the larvicidal activity of Ag-NPs produced using Streptomyces diastaticus against Culex quinquefasciatus, Anopheles stephensi, Aedes aegypti, Spodoptera litura, and Plutella xylostella. UV-Vis spectroscopy, XRD, SEM-EDX, FT-IR, TEM, DLS, and Zeta potential analysis were used to characterize the biosynthesized Ag-NPs. The results showed that biosynthesized Ag-NPs were more toxic to, A. stephensi, C. quinquefasciatus, and A. aegypti with LC50 values of 15.70, 11.10, and 17.53µg/mL, respectively. Biosynthesized Ag-NPs exhibited the highest antifeedant effects against S. litura (88.73%) and P. xylostella (92.36%) at 50µg/mL concentration. The mortality bioassay revealed considerable larvicidal activity against S. litura and P. xylostella larvae at greater doses of 50µg/mL, 80.67 and 84.05%, respectively. Morphogenetic variations were observed on treated larvae of C. quinquefasciatus, A. aegypti, and A. stephensi, S. litura, and P. xylostella with Ag-NPs. In the present investigation the impact of Ag-NPs on the antioxidant enzymes (SOD, CAT, and GPx), the activity of each enzyme were dramatically increased with higher concentrations resulting in significant differences. The study also found that Ag-NPs inhibited the detoxifying enzyme (GST and AChE) activity of target organisms. The histological structure of the treated and untreated larvae revealed structural changes between the midgut epithelial cells. As a consequence of these findings, the S. diastaticus-mediated Ag-NPs serve as a possible, eco-friendly biopesticide and alternative to synthetic chemicals for the control of human vector mosquitoes and destructive arthropod insect pests.

Bacillus velezensis LY7 promotes pepper growth and induces resistance to Colletotrichum scovillei

Anthracnose of pepper (Capsicum annuum L), caused by Colletotrichum scovillei, is one of the three major diseases of pepper that seriously impact yield and quality. As an alternative to the use of synthetic chemical pesticides, a variety of endophytic bacteria have been reported to be potential biocontrol agents with the ability to improve disease resistance and abiotic stress tolerance in host plants. However, the mechanisms of action by which these different bacterial biocontrol agents inhibit the onset and development of disease, in some cases, remains unclear. In the present study, the potential use of the endophytic bacterial strain Bacillus velezensis LY7, originally isolated from pepper leaves, as a biocontrol agent was evaluated. More specifically, the ability of LY7 to control anthracnose in pepper and promote growth was assessed in pot experiments in a greenhouse and in vitro assays. Results indicated that the use of B. velezensis LY7 enhanced the synthesis of jasmonic acid and other hormones in pepper plants, as well as increased disease resistance and plant growth. A 200 × dilution of LY7 fermentation broth reduced disease incidence up to 90.70 %, while also enhancing plant growth. The mechanism of action of LY7 was also evaluated. Results indicated that LY7 secreted an antibiotic protein possessing a cupin domain OS. RNA-sequence analysis of the transcriptome of C. scovillei at several timepoints after exposure to LY7 (24, 48, and 72 h) revealed the up- and down-regulation of several genes. More specifically, LY7 induced the expression of genes associated with biosynthesis pathways and transcription factors involved in anthracnose pathogenicity. Our results indicate that the LY7 strain of induces hormone synthesis in pepper plants that results in enhanced disease resistance and promotes growth, as well as enhances stress tolerance by enhancing antioxidant and defense-related enzyme activity. These results demonstrate the potential of using LY7 for the biocontrol of anthracnose in pepper plants.

Heterologous production of the insecticidal pea seed albumin PA1 protein by Pichia pastoris and protein engineering to potentiate aphicidal activity via fusion to snowdrop lectin Galanthus nivalis agglutinin; GNA)

BackgroundNew bioinsecticides with novel modes of action are urgently needed to minimise the environmental and safety hazards associated with the use of synthetic chemical pesticides and to combat growing levels of pesticide resistance. The pea seed albumin PA1b knottin peptide is the only known proteinaceous inhibitor of insect vacuolar adenosine triphosphatase (V-ATPase) rotary proton pumps. Oral toxicity towards insect pests and an absence of activity towards mammals makes Pa1b an attractive candidate for development as a bioinsecticide. The purpose of this study was to investigate if Pichia pastoris could be used to express a functional PA1b peptide and if it’s insecticidal activity could be enhanced via engineering to produce a fusion protein comprising the pea albumin protein fused to the mannose-specific snowdrop lectin (Galanthus nivalis agglutinin; GNA).ResultsWe report the production of a recombinant full-length pea albumin protein (designated PAF) and a fusion protein (PAF/GNA) comprised of PAF fused to the N-terminus of GNA in the yeast Pichia pastoris. PAF was orally toxic to pea (Acyrthosiphon pisum) and peach potato (Myzus persicae) aphids with respective, Day 5 LC50 values of 54 µM and 105 µM derived from dose–response assays. PAF/GNA was significantly more orally toxic as compared to PAF, with LC50 values tenfold (5 µM) and 3.3-fold (32 µM) lower for pea and peach potato aphids, respectively. By contrast, no phenotypic effects were observed for worker bumble bees (Bombus terristrus) fed PAF, GNA or PAF/GNA in acute toxicity assays. Confocal microscopy of pea aphid guts after pulse-chase feeding fluorescently labelled proteins provides evidence that enhanced efficacy of the fusion protein is attributable to localisation and retention of PAF/GNA to the gut epithelium. In contact assays the fusion protein was also found to be significantly more toxic towards A. pisum as compared to PAF, GNA or a combination of the two proteins.ConclusionsOur results suggest that GNA mediated binding to V-type ATPase pumps acts to potentiate the oral and contact aphicidal activity of PAF. This work highlights potential for the future commercial development of plant protein-based bioinsecticides that offer enhanced target specificity as compared to chemical pesticides, and compatibility with integrated pest management strategies.

Botanical pesticide ability to control black pod rot of cacao Phytophthora palmivora (Butl.) Butl in the field

The use of synthetic chemical pesticides for cacao black pod rot disease control to remove heavy metal residues on cacao beans needs to be reduced. This research aimed to find out the ability of botanical pesticides to lower BPR incidence, BPR infection rate, and botanical pesticides’ efficacy in controlling BPR. It was conducted at the Cacao Research Substation Garden of the Plantation and Horticulture Office of Southeast Sulawesi. The treatments experimented included control (no pesticide), CNSE, CNSE + CSLS, CNSE + whiteflower albizia bark extract, CNSE + siam weed leaf extract, CNSE + candle bush leaf extract, CNSE + whiteflower albizia bark extract + siam weed leaf extract + candle bush leaf extract, and synthetic pesticide with active ingredient copper oxysulfate at 345 g/L. Group-randomized trial was used as design in triplicate. The research results showed that the botanical pesticides of CNSE, and the was mixture with of CSLS, siam weed leaf extract, candle bush leaf extract, and whiteflower albizia bark extract were able to lower the disease incidence and slow down the infection rate of BPR. The lowest BPR incidence and infection rates were discovered in the CNSE + Siam weed leaf extract treatment, each at 38.90% and 0.087 per pod per week. The CNSE botanical pesticide mixed with Siam weed leaf extract, whiteflower albizia bark extract, and candle bush leaf extract demonstrated good efficacy above 50%, hence feasible to use as an alternative to chemical pesticides in BPR control.

Double transplantation as a climate resilient and sustainable resource management strategy for rice production in eastern Uttar Pradesh, north India

-Enhancing the productivity of rainfed crops, especially rice, while coping with climate adversities and saving critical natural resources is essential for ensuring the food and nutrition security of a growing population. With this context, the present study was undertaken to validate promising farm innovation and adaptation practices used by small-medium landholding farmers for rice cultivation in eastern Uttar Pradesh (UP), north India, as well as to examine the sustainability of innovative practices for large-scale adoption. For this, a 3-year study comprising extensive field surveys and experiments was undertaken to compare single transplantation (ST) and double transplantation (DT) in rice along with organic addition (farm-yard manure, FYM) on crop growth, yield, climate resilience, soil quality, and overall sustainability i.e., social (women involvements and labour productivity), environmental (water productivity and nutrient use efficiency), and economic (benefit:cost ratio) dimensions of sustainability. Field experiments were conducted in triplicate using two local rice varieties (MotiNP-360 and Sampurna Kaveri) in two agroclimatic zones, namely the middle Gangetic plains and the Vindhyan zone, in the Mirzapur district of eastern Uttar Pradesh. The DT practices of rice with and without farm yard manure (FYM) (replacing at a dose of 25% NPK) were evaluated over conventional methods of rice cultivation (i.e., ST, as control) and analysis was done periodically. The DT practice improved growth (p < 0.05), percent fertile tiller and grain (p < 0.05), and rice yield (15–20% higher than ST), while also improving soil quality, yield indices, water and labour productivity, and the benefit-cost ratio. The DT practice also resulted in early maturity (10–15 days earlier than ST), created more labour days for women, decreased lodging and pest/disease incidence, as well as a subsequent reduction in the use of synthetic chemical pesticides and associated environmental costs. Importantly, the residual effects of FYM application significantly improved (p < 0.05) the grain yield in subsequent years of cropping. Optimizing DT cultivation practices, preferably with FYM input for various agro-climatic regions, is essential for large-scale sustainable rice production under changing climatic conditions.

Pomelo seed oil: Natural insecticide against cowpea aphid.

Cowpea aphid (Aphis craccivora Koch) is a plant pest that causes serious damage to vegetable crops. Extensive use of synthetic chemical pesticides causes deleterious effects on consumers as well as the environment. Hence, the search for environmentally friendly insecticides in the management of cowpea aphids is required. The present work aims to investigate the aphicidal activity of pomelo seed oil (PSO) on cowpea aphids, the possible insecticidal mechanisms, its chemical constituent profile, as well as the toxicity of its primary compounds. The results of the toxicity assay showed that PSO had significant insecticidal activity against aphids with a 72-hour LC50 value of 0.09 μg/aphid and 3.96 mg/mL in the contact and residual toxicity assay, respectively. The enzymatic activity of both glutathione S-transferase (GST) and acetyl cholinesterase (AChE) significantly decreased, as well as the total protein content, after PSO treatment, which suggested that the reduction of AChE, GST, and the total protein content in aphids treated with PSO might be responsible for the mortality of A. craccivora. The GC-MS analysis revealed that PSO contained limonene (22.86%), (9Z,12Z)-9,12-octadecadienoic acid (20.21%), n-hexadecanoic acid (15.79%), (2E,4E)-2,4-decadienal (12.40%), and (2E,4Z)-2,4-decadienal (7.77%) as its five major compounds. Furthermore, (9Z,12Z)-9,12-octadecadienoic acid showed higher toxicity to aphids than both PSO and thiamethoxam (positive control). This study emphasized the potential of PSO as a natural plant-derived insecticide in controlling cowpea aphids and also provided a novel approach for the value-added utilization of pomelo seed.

In Silico Study of Eugenol and trans-Caryophyllene also Clove Oil Fumigant Toxicity on Tribolium castaneum

Alternative storage pest control that is more environmentally friendly than the use of synthetic chemical pesticides is to use botanical pesticides from plant essential oils, including clove (Syzygium aromaticum) which contains the main compounds eugenol and trans-caryophyllene. To study the various mechanisms of action of essential oils as botanical insecticides could use in silico approach through molecular docking. This study aims to predict the dominant binding mode(s) of a ligand with a protein of a known three-dimensional structure through docking. Then tested its fumigant activity on Tribolium castaneum. The docking results showed that the trans-caryophyllene and eugenol compounds had a more stable bond strength in the acetylcholinesterase enzyme T. castaneum than the control compound linalool. In addition, there is a synergy between eugenol and trans-caryophyllene when the two compounds interact with acetylcholinesterase. These results can be used as prediction material that trans-caryophyllene and eugenol have potential as protein acetylcholinesterase inhibitors of T. castaneum. After being tested in the laboratory, clove oil which contains two main compounds namely eugenol and trans-caryophylene has the potential to control T. castaneum with an LC50 value of 5,227 μL/L air. Keywords: Botanical insecticide, Caryophyllene, Docking, Eugenol, Fumigant,Syzygium aromaticum

Methyl Benzoate as a Promising, Environmentally Safe Insecticide: Current Status and Future Perspectives

The widespread use of synthetic chemical pesticides beginning in the late 1930s has contributed to the development of insecticide resistance of many important species of pest insects and plants. Recent trends in pesticide development have emphasized the use of more environmentally benign control methods that take into consideration environmental, food safety, and human health. Biopesticides (e.g., naturally occurring pesticidal compounds) are alternative pest management tools that normally have no negative impact on human health or the environment. Here we review methyl benzoate, a relatively new botanical insecticide that occurs naturally as a metabolite in plants, and whose odor is an attractant to some insects. Since 2016, many studies have shown that methyl benzoate is an effective pesticide against a range of different agricultural, stored product, and urban insect pests. Methyl benzoate has several important modes of action, including as a contact toxicant, a fumigant, an ovicidal toxin, an oviposition deterrent, a repellent, and an attractant. In this review, we summarize various modes of action of methyl benzoate and its toxicity or control potential against various kinds of arthropods, including agricultural pests and their natural enemies, and pollinators. We conclude that methyl benzoate is a very promising candidate for use in integrated pest management under either greenhouse or field conditions.

Larvicidal activity of selected medicinal plants against dengue vector Aedes aegypti

The use of synthetic chemical pesticides to control mosquitoes has resulted in a slew of issues, including practical, ecological, insecticide susceptibility, financial, and toxicity to co-inhabitant organisms. Therefore, new ways for eradicating Aedes aegypti using medicinal plant active bio compounds. The purpose of this study was to assess the larvicidal effectiveness of Aegle marmelos and Coleus aromaticus plants methanolic extracts against Ae. aegypti larvae and pupa. The 24 hour LC50 values for II, III, IV instars, and pupa for methanolic solvent leaf extracts of A. marmelos are 124.27ppm, 145.07ppm, 178.87ppm, and 225.99ppm, respectively. The LC50 value for C. aromaticus plant extract was 62.46 ppm in the II instar, 81.94 ppm in the III instar, 101.19 ppm in the IV instar, and 124.34 ppm in the pupa. A. marmelos II, III, IV instars, and pupa have LC90 values of 222.74ppm, 283.43ppm, 354.02ppm, and 439.73ppm, respectively, after 24 hr. C. aromaticus, respectively, 162.87 ppm for the II instar and 202.83ppm for the III instar.213.63 for the IV instar and 254.14ppm in the pupa.

UJI EFEKTIFITAS EKSTRAK BIJI PINANG (Arecha cathecu L.) TERHADAP MORTALITAS HAMA PENGGEREK POLONG KEDELAI (Etiella zinckenella Treitschke) DI LABORATORIUM

Pod Borer ( Etiella zinckenella ) is a major pest in soybean cultivation. The chemical pesticides used in agriculture are causing various detrimental effects on our health as well as on environment. Botanical pesticides such as betel nut ( Areca catechu L.) is an alternative pest control to reduce the use of synthetic chemical pesticides. This research was conducted in the plant pest laboratory, Faculty of Agriculture, Riau University. This study was conducted in order to found a concentration of betel nut seed extract ( Areca catechu L.) which is effective to control E. zinckenella in soybean crops. The experiment using a completely randomized design with six treatments. Betel nut seed extract concentration are 0 g L -1 of water, 20 g L -1 of water, 40 g L -1 of water, 60 g L -1 of water, 80 g L -1 of water, and 100 g L -1 of water and each treatment was repeated four times. The result showed 40 g L -1 of water of betel nut seed extract is effective concentration and able to kill 80% E. zinckenella larvae.

Insecticidal Activities Against Odontotermes formosanus and Plutella xylostella and Corresponding Constituents of Tung Meal from Vernicia fordii.

Simple SummaryOdontotermes formosanus (Shiraki) (O. formosanus) and Plutella xylostella (Linnaeus) (P. xylostella) are common industrial and agricultural pests with a wide distribution range, multiple host species, few natural predators, and rapid reproduction. The control of these pests relies heavily on synthetic chemical pesticides; however, environmental pollution and the rise of insect resistance induced by the excessive use of synthetic chemical pesticides pose serious challenges. The present study was designed to systematically evaluate the insecticidal activities of different extracts of tung meal against the above two pests and to reveal the chemical constituents of the main active parts. The result confirmed the remarkable insecticidal activity of tung meal and provided a theoretical basis for its development as a potential plant insecticide.The environmental pollution, pesticide resistance, and other associated problems caused by traditional chemical pesticides with limited modes of action make it urgent to seek alternative environmentally-friendly pesticides from natural products. Tung meal, the byproduct of the detoxified Vernicia fordii (Hemsl.) seed, has been commonly used as an agricultural fertilizer and as a pesticide. However, its active insecticidal extracts and ingredients remain elusive. In the present study, the contact toxicities of tung meal extracts against the agricultural and forest pests like O. formosanus and P. xylostella were examined. Our results showed that ethyl acetate and petroleum ether extracts showed the strongest toxicity against O. formosanus and P. xylostella, respectively. In order to further explore the chemical profiles of the ethyl acetate and petroleum ether extracts, UPLC-Q/TOF-MS and GC-MS analyses have been performed, and 20 and 29 compounds were identified from EA and PE extracts, respectively. The present study, for the first time, verified the noteworthy insecticidal activities on the aforementioned agricultural and forest pesticides and revealed the potential active parts and chemical composition, which are conducive to further exploiting the potential of tung meal as a natural plant-derived insecticide for biological control of agricultural and forest pests.

PEMANFAATAN METABOLIT SEKUNDER TUMBUHAN SEBAGAI PESTISIDA NABATI PADA HAMA TANAMAN HUTAN

The use of chemical pesticides is often carried out in excessive doses, so that this condition results in increased accumulation of pesticide residues in nature. The residue can kill non target organisms, there was an explosion of secondary pests and pest resistance. One effort to reduce the use of synthetic chemical pesticides is by substitution using botanical pesticides that are more environmentally friendly. Botanical pesticides that are easily biodegradable in nature, so it does not pollute the environment, it is relatively safe for humans and the presence of natural enemies. One of the most potential types of botanical pesticides is from the Meliaceae family, namely neem, mahogany, and suren. In this study, the content of secondary metabolites was tested for neem, mahogany and suren seeds. Toxicity properties against pests conducted through literature searches. The purpose of this study was to obtain information on the toxicity and content of secondary metabolite compounds from the three plant seed extracts against forest pests. The results showed that the extract of neem, mahogany and suren seeds contain compounds secondary metabolites from the saponins, tanins, flavonoids, alkoloids, and terpenoids. The compounds can be used as botanical pesticides to control pests of forest plants.

ENTOMOTOXICANT POTENTIAL OF ARAK SHOOT EXTRACT FOR THE CONTROL OF EPHESTIA CAUTELLA

The date, palm, Phoenix dactylifera is the most significant agricultural product in the Middle East region, in which Saudi Arabia is ranked as the top producing country. One of the most critical problems facing date production is insect infestation. Ephestia cautella is one of the most harmful insects to date, causing significant damage. Different techniques have been used against E. cautella through the use of synthetic chemical pesticides, but they have a negative impact on the environment. Recently, research has been directed towards seeking alternatives to these methods.In the current study, a biological system using Salvadora persica shoot extract for the control of E.cautellahas been evaluated. To this end, mortality rates LD50 and LD90 were determined when the different concentrations of the plant extract were applied at different developmental stages (larvae, pupa, and adult male/female) over a period of three days. Furthermore, some chemical constituents of the plant extract were determined by preliminary chemical tests and by using Gas chromatography–mass spectrometry (GC-MS). Results from current investigation have displayed that the mortality rate was dependent on both the developmental stage and concentrations of the plant extract. Total phenolics and the saponin content of the plant extract were detected. GC-MS analysis identified the potential chemical agents in the plant extract that may possess the insecticidal ability. In light of the current findings, it is clear that infestation of date palms by E.cautella can be controlled by using S. persica shoot extract. To optimize the implementation of this technique, we recommend that future research focus on testing other organic solvents and other plant parts so that the most biologically active biomolecules responsible for the control of E. cautella under date storage conditions can be accurately determined.

Effect of Gut Microbes from Eyprepocnemis alacris alacris (Serv. 1838) against Culex quinquefasciatus Say - An Ecofriendly Approach

Mosquitoes are on focus worldwide because of its role as vectors for devastating parasites and pathogens causing a threat to millions of people worldwide. Vector-borne diseases in mosquitoes are transmitted by females. However, ineffectiveness of insecticides increases the resistance in mosquitoes. The administration of new vector control strategies against the mosquitoes needs the implementation of microbial insecticides. In this study was commenced to determine the mortality of larvae using gut bacteria as of Eyprepocnemis alacris alacris (Serville, 1838) conflict to larvae laboratory conditions to identify an effective bacteria. The results indicated the existence of larvicidal activity in 106 isolates and were found to appear strongly effective activity in three isolates against Cx. quinquefasciatus. Cent per cent mortality was observed from each of the secondary metabolites. The recorded values of LC50 were 6.66, 7.13 and 7.64ppm and LC90 has been 115.90, 205.73 and 242.59 ppm respectively. The sequencing and phylogenetic analysis confirmed that these 3 isolates were identified as Klebsiella pneumoniae, Enterobacter xiangfangensis and Ochrobactrum intermedium respectively. Our results showed high larvicidal potential effect against to these bacteria. Outcome of these work highlight the alternative use of synthetic chemical pesticides to control mosquitoes.

Pengendalian Hama Penyakit Terpadu untuk Mengurangi Kerusakan pada Tanaman Padi di Desa Mekar Sari Kecamatan Gunung Sari

Until now farmers still use synthetic chemical pesticides in eradicating pests and diseases. On the one hand, the use of synthetic chemical pesticides is beneficial because of the poison power or the ability to kill pests and diseases that are high and fast, but the excessive use of toxic pesticides, in addition to the increasingly resistant pests and diseases to pesticide poisons, can also pollute the environment. In addition, pesticide poisons tend to increase in price, so that economically it does not increase production value. Community service is carried out in the form of agricultural counseling, carried out in Mekar Sari Village, Gunung Sari District, aiming that farmers have better knowledge and are willing to implement integrated pest and disease control (IPM) methods on rice plants. This counseling material was delivered with lecture techniques, then followed by question and answer sessions. The agricultural extension activities in Mekar Sari Village, Gunung Sari Subdistrict went smoothly and most of the extension participants were able to increase their knowledge to be better, so that they were expected to increase their understanding and be able to apply the technology

Growth and viability of entomopathogenic fungus Beauveria bassiana (Balsamo) Vuillemin in different alternative media

At present, the use of synthetic chemical pesticides become a threat to the biotic and abiotic environment. The use biological agents such as entomopathogen may become an alternative in supporting integrated pest management. One of entomopathogenic fungus that has been used in controlling pests is Beauveria bassiana. However, a good alternative media for the growth of B. bassiana is required to produce more optimal conidia density and germination. This study was aimed to determine the effect of several media on the growth of B. bassiana and its conidial density. The method used in this study was compeletely randomized design with 5 replications. The experimental treatment consisted of PDA, maize, rice, and mungbean. The result showed that there was no significant differences among maize, mungbean, and PDA media in supporting the growth of B. bassiana, with the means of colonies diameter at 8.91 cm, 8.89 cm, and 9.00 cm, respectively. Moreover, the growth rate, conidia density, and viability of the alternative media were not significantly different with PDA. Therefore, further research to determine other alternative media for the growth and viability of B. bassiana is needed.

Research and Development of Biopesticides: Challenges and Prospects

Even though pesticides have greatly contributed to boosting agricultural productivity and farmer income over the years, there have been concerns about the safety of some of these pest control products. Besides, there has been a growing demand for good quality and safe food in the recent past – as reflected in the stringent regulations on pesticide residue levels in produce. Biopesticides in comparison with conventional synthetic chemical pesticides are usually less toxic, generally affect only the target pest and closely related organisms, are often effective in relatively small quantities and decompose faster, resulting in lower exposure. Consequently, over the last few years, biopesticides have attracted global attention as a safer pest control strategy for incorporation into Integrated Pest Management (IPM) programmes. Besides, in the last decade, adoption of IPM programmes has significantly enhanced pest management practices and, in some cases, reduced pesticide use, consequently reducing the rise in demand for synthetic chemical pesticides. Also, the development of new synthetic chemical pesticides has declined considerably in the recent past, as regulations have become tighter, with products being withdrawn from the market, resulting in a more limited choice of chemical solutions such that biopesticides have become a more feasible option. Many countries have also increasingly lowered chemical Maximum Residue Levels for agricultural imports which have made it increasingly necessary to explore pest control options which would ensure reduced reliance on the use of synthetic chemical pesticides. In this paper, avenues of addressing challenges to biopesticide research and development are evaluated by seeking the inputs of a wide range of stakeholders, building on a recent international workshop with biopesticides practitioners from across the globe. Prospects for biopesticide application are detailed using a case study on the fall armyworm (Spodoptera frugiperda) in Africa.

Screening and partial characterization of d-endotoxins from some local Bacillus thuringiensis isolates for insecticidal activity against the spotted stem borer

Abstract. Kimani PG, Nyambaka H, Kasina M. 2018. Screening and partial characterization of d-endotoxins from some local Bacillus thuringiensis isolates for insecticidal activity against the spotted stem borer. Biofarmasi J Nat Prod Biochem 17: 21-38. Prolonged use of synthetic chemical pesticides is environmentally undesirable, causing the rapid development of resistance among insect pests. Kenya has unexplored potential in controlling lepidopteran pests by using proteinous delta-endotoxins sourced from local isolates of a naturally occurring bacterium, Bacillus thuringiensis Berliner (Bt). This study attempted to identify the insecticidal proteins in some Kenyan Bt isolates, characteristic of Cry1 and/or Cry2 proteins. It also aimed to test their efficacy as affected by different temperatures and their specificity on an invasive and prevalent lepidopteran stem borer, Chilo partellus (Swinhoe). Delta-endotoxin crystals were isolated and purified from cultures of twenty unidentified local Bt isolates using froth floatation and centrifugation. Total protein in the resulting suspensions was quantified using the Bradford assay method, and the approximate protein yield was 3.14 ±0.084 mg/mL of nutrient broth culture with a purity level of 54.8 % ±15.3 %. Leaf-dip bioassays used for testing the efficacy of the d-endotoxins against C. partellus. Among the isolates evaluated, Bt 44 and Bt 48 had the most potent d-endotoxin crystals towards the 1st instar larvae, leading to mortality of 62.6 % and 64.8 % respectively after 72 h. The effect of the d-endotoxins' concentration and temperature on larval mortality was examined for 72 hours at temperatures of 24°C, 27°C and 31°C and levels of 0.01 mg/mL, 0.1 mg/mL and 1.0 mg/mL. The resulting LC50 was 52.3 µg/mL and 42.0 µg/mL, while LT50 values were 76.7h and 60.9h for Bt 44 and Bt 48, respectively. Higher efficacy found at 24°C and 31°C than at 27°C, an indication that these d-endotoxins are tolerable for local conditions where temperatures are higher than in temperate regions. The relationship between concentration and temperature was significant for d-endotoxins of Bt 48 but not those of Bt 44. A major protein component of the d-endotoxins had a molecular weight Mr ~ 130 kDa, which generates a trypsin-resistant core of Mr ~ 70 kDa. Cry protein analysis detected more Cry1 in Bt 44 than Bt 48 ?-endotoxins and no Cry2 in either. However, cry gene analysis using PCR detected the presence of both cry1 and cry2 genes in the DNA of Bt 44 but none in Bt 51, a negative control from toxicity tests against the pest. The chromatographic analysis revealed some differences in the elution profiles of d-endotoxins of both Bt 44 and Bt 48, an indication that there may be different types and amounts of the Cry toxins in the crystals or even novel proteins. These findings indicate that the two local Bt isolates expressed Cry1, and probably Cry2 proteins can control C. partellus and may, therefore, become promising sources for ?-endotoxins for biopesticide development for controlling the pest.

Push-Pull Farming System Controls Fall Armyworm: Lessons from Africa

Fall armyworm (FAW) Spodoptera frugiperda invaded Africa, with the first detections being reported in Central and Western Africa in early 2016, and now affects at least 40 countries in Africa, causing up to total crop loss amounting to over $6.2 billion p.a. FAW is an invasive polyphagous pest that causes damage to economically important crops and has recently been reported in the Indian sub-continent. Effective control of FAW through use of synthetic chemical pesticides and genetically modified crops such as Bt maize faces challenges including improper use, unaffordability by smallholder farmers and development of resistance by the pest. Additionally, dispersal of FAW larvae into the lower maize plant canopy keeps them out of reach of topical insecticide applications. Integrated pest management (IPM) packages like the push-pull technology which eliminate pesticide use, and deploy natural processes are more suitable and cost-effective. Push-pull is a farming system intensification approach that involves attracting insect pests with trap plants (pull) such as Napier grass (Pennisetum purpureum) or Brachiaria grass, while driving them away from the main crop using a repellent intercrop (push), Desmodium spp., commonly known as desmodium, and attracting natural parasitoids and predators to the field. In the rhizosphere, chemicals secreted by desmodium roots inhibit attachment of germinated striga to maize or sorghum roots and abort germination of striga seeds which are rapidly depleted in the soil. Moreover, it improves soil fertility by fixing nitrogen, improving carbon sequestration, organic matter, moisture retention, and soil biota, and prevents further degradation of soil. The climate-adapted push-pull technology significantly reduces plant damage by FAW and is the first IPM management tool for the pest in Africa, and is well suited to agro-ecosystem intensification needs of smallholder mixed farming systems in Africa and beyond. Both the African and the Asian continents provide favourable climatic conditions for sustained reproduction of the FAW, which is expected to result in severe damage to crops; and being a new pest in both continents, it might have few natural enemies. Conventional control methods have limited effectiveness, as explained above. Therefore, an IPM approach that is compatible with mixed cropping farming systems of small and medium scale farmers is necessary. The climate adapted push-pull is the first demonstrated IPM management tool for the FAW in Africa. The technology combines this with other concomitant benefits including control of stemborers and the parasitic striga weeds, improvement of soil health through factors such as nitrogen fixation by desmodium, natural mulching, moisture retention and improvement of soil organic matter and soil biota. The combined benefits, including control of FAW, result in ecologically sustainable higher crop yields, and well suited to agro-ecosystem intensification needs of smallholder mixed farming systems in Africa and beyond.

Toxicity and enzyme inhibition activities of the essential oil and dominant constituents derived from Artemisia absinthium L. against adult Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera: Psyllidae)

The extensive use of synthetic chemical pesticides has led to negative effects on the environment and human health. Therefore, scientists are in search of natural products, especially those from plant sources, which are less hazardous, eco-friendly, and effective alternatives to the conventional pesticides. Essential oils are potential alternatives to the synthetic chemical pesticides. However, the toxicity of Artemisia absinthium against Asian citrus psyllid Diaphorina citri has not been documented. Therefore, here we focused on the A. absinthium essential oil (ABEO) extracted from the population grown under the climatic conditions of Pakistan’s high plateaus, as a natural pesticide for the control of the citrus psyllid. The results indicated that the oil caused significant acute mortalities in both topical and residual contact applications, with 50% lethal dose (LD50) and 50% lethal concentration (LC50) values of 5.2 μg/insect and 24.4 mg/mL. Among the constituents tested only carvacrol, (−)-α-bisabolol and chamazulene were toxic, with LD50 values of 6.9, 8.2, and 10.3 μg/insect via topical application and LC50 values of 28.5, 33.5, and 39.4 mg/mL via residual contact exposure. Several combinations of dominant constituents were both additive and synergistic when applied topically, especially carvacrol + (−)-α-bisabolol + chamazulene (1:1:1) displayed synergistic effect, with a poison ratio of 1.39. Furthermore, the essential oil and carvacrol inhibit acetylcholinesterase activity in citrus psyllid. It has been concluded that the essential oil and some of the compounds from A. absinthium might be developed as eco-friendly approaches for the control of citrus psyllid.