Use Of Insecticides Research Articles

Ecologically Based Management of Pineapple Mealybug Wilt: Controlling Dysmicoccus brevipes Mealybug Populations with Salicylic Acid Analogs and Plant Extracts

Mealybug wilt of pineapple (MWP) is a destructive disease worldwide caused by a parasitic complex that includes Pineapple Mealybug Wilt-associated Viruses (PMWaVs) and mealybugs (Dysmicoccus brevipes), which concurrently act as vectors for these viruses. Reducing the mealybug population is key to managing MWP, which is achieved in intensive production systems through the use of insecticides. SA (salicylic acid), ASM (acibenzolar-S-methyl), BABA (β-aminobutyric acid), and MeSA (methyl salicylate) are key components of systemic acquired resistance (SAR), the defense mechanism of plants against biotrophic agents such as mealybugs. In this study, these compounds were applied either as pure chemicals and/or as a major constituent of plant extracts. Both the Hawaiian hybrid MD-2 and Queen Victoria tissue culture plants, as well as suckers used for vegetative propagation, were treated with these compounds by direct application on the soil of pineapple pots. Subsequently, five mealybugs were released on each plant or each daughter plant in case of a transgenerational experiment; then, after 45 days, the number of mealybugs was counted. Exogenous SA, ASM, and MeSA reduced the population of mealybugs by a minimum of 50% and up to 80%. These SAR-inducing treatments could be an interesting alternative for controlling mealybugs and are already used in other pathosystems. The SAR mechanisms behind this effect are yet to be confirmed by molecular and enzymatic markers. ASM and MeSA are promising treatments for pineapples using tissue culture plants or traditional shoots.

Compatibility of Entomopathogenic Nematodes with Chemical Insecticides for the Control of Drosophila suzukii (Diptera: Drosophilidae).

The spotted-wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), is a pest that reduces the productivity of small fruits. Entomopathogenic nematodes (EPNs) and chemical insecticides can suppress this pest, but the compatibility of the two approaches together requires further examination. This laboratory study evaluated the compatibility of Steinernema brazilense IBCBn 06, S. carpocapsae IBCBn 02, Heterorhabditis amazonensis IBCBn 24, and H. bacteriophora HB with ten chemical insecticides registered for managing D. suzukii pupae. In the first study, most insecticides at the recommended rate did not reduce the viability (% of living infective juveniles (IJs)) of S. braziliense and both Heterorhabditis species. The viability of S. carpocapsae was lowered by exposure to spinetoram, malathion, abamectin, azadirachtin, deltamethrin, lambda-cyhalothrin, malathion, and spinetoram after 48 h. During infectivity bioassays, phosmet was compatible with all the EPNs, causing minimal changes in infectivity (% pupal mortality) and efficiency relative to EPN-only controls, whereas lambda-cyhalothrin generally reduced infectivity of EPNs on D. suzukii pupae the most, with a 53, 75, 57, and 13% reduction in infectivity efficiency among H. bacteriophora, H. amazonensis, S. carpocapsae, and S. brazilense, respectively. The second study compared pupal mortality caused by the two most compatible nematode species and five insecticides in various combinations. Both Heterorhabditis species caused 78-79% mortality among D. suzukii pupae when used alone, and were tested in combination with spinetoram, malathion, azadirachtin, phosmet, or novaluron at a one-quarter rate. Notably, H. bacteriophora caused 79% mortality on D. suzukii pupae when used alone, and 89% mortality when combined with spinetoram, showing an additive effect. Novaluron drastically reduced the number of progeny IJs when combined with H. amazonensis by 270 IJs and H. bacteriophora by 218. Any adult flies that emerged from EPN-insecticide-treated pupae had a shorter lifespan than from untreated pupae. The combined use of Heterorhabditis and compatible chemical insecticides was promising, except for novaluron.

Identification of an Entomopathogenic Fungus, Pseudozyma flocculosa (Traquair, Shaw & Jarvis), and Its Efficacy against Tetranychus urticae Koch

The two-spotted spider mite, Tetranychus urticae Koch, is one of the most important agricultural pests worldwide, with chemical application being the primary control method. However, frequent heavy use or misuse of insecticides has accelerated the development of varying degrees of resistance in T. urticae. This makes the chemical control of this mite more challenging. Biocontrol methods have attracted much attention due to their safety and environment-friendly impact. Based on previous observations that the population of T. urticae was infected by unknown pathogenic fungi, we isolated, identified, and evaluated the pathogenicity of the fungi from infected mites. Through available morphological and molecular identification, the fungus was identified as Pseudozyma flocculosa. The virulence activity of the strain was evaluated at different concentrations of spore suspension (106–109 conidia/mL) using a spraying method. The strain showed pathogenic activity against the T. urticae in adult females that varied with different concentrations and temperatures. Meanwhile, the P. flocculosa also had a significant toxic effect on the developmental stages of T. urticae. In the laboratory bioassay, the mortality rate of the tested mites reached 100% at 9 d after P. flocculosa treatment. Additionally, a wettable powder processed with P. flocculosa conidia was applied on the T. urticae in the greenhouse and the control efficacy reached up to 90% at 7 d after treatment. The results showed a high insecticidal activity of P. flocculosa against T. urticae, indicating that this fungus possesses great potential for use as a bio-insecticidal agent.

AsOBP1 is required for bioallethrin repellency in the malaria vector mosquito Anopheles sinensis.

The use of insecticides, primarily pyrethroids, is a pivotal strategy for mosquito control globally. Bioallethrin, the first commercially available volatile pyrethroid, can elicit spatial (i.e., noncontact) repellency to mosquitoes through the coactivation of olfactory receptor neurons and sodium channels. However, the olfactory mechanism of the repellency elicited by bioallethrin in mosquitoes is still unclear. Here, we demonstrated the involvement of AsOBP1 in the bioallethrin repellency in Anopheles sinensis, one of the main vectors of vivax malaria in China and other Southeast Asian countries. The behavioral and electrophysiological analyses in AsOrco-/- mutant found that the spatial repellency elicited by bioallethrin depended on the odorant receptor (OR)-mediated olfactory pathway. Furthermore, the repellency was reduced in the AsOBP1-/- mutant and a pyrethroid-resistant strain, in which the expression of AsOBP1 was significantly decreased. Moreover, recombinant AsOBP1 protein bound to bioallethrin in an in vitro competition assay. These results indicate that activation of the AsOBP1-mediated olfactory pathway is an important component of bioallethrin repellency. Our research lays the foundation for further elucidation into the olfactory mechanism of bioallethrin repellency and the behavioral modifications of pyrethroid-resistant mosquitoes.

Insecticide resistance status of Aedes aegypti in border areas of Yunnan Province.

Aedes aegypti is a main vector of arboviral diseases, principally dengue, chikungunya, and Zika. Insecticides remain the most effective vector control method. Pyrethroid is the main insecticide currently used, and the long-term use of insecticides can cause mosquitoes to develop knockdown resistance. Studying the mutation sites and genotypes of Ae. aegypti can reveal the mutation characteristics and regional distribution of the kdr gene in an Ae. aegypti population. Testing for a correlation between the mutation rate in various populations and pyrethrin resistance can clarify the resistance mechanism. The bioassay results showed that all 15 populations are resistant. In the study of the kdr gene, three non-synonymous mutations were identified in the DNA of first generation females from the wild Ae. aegypti population: S989P (TCC-CCC), V1016G (GTA-GGA), and F1534C (TTC-TGC). The mortality rate of the various populations was correlated with the mutation rate at the V1016G + F1534C locus, but not the S989P + V1016G locus. Aedes aegypti populations in border regions of Yunnan Province are resistant to permethrin and beta-cyfluthrin. The insecticidal effect of beta-cyfluthrin is stronger than that of permethrin. The mutation rate at sites V1016G + F1534C is negatively correlated with the mortality of Ae. aegypti based on bioassays. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The efficacy of botanical pesticides in controlling coffee berry borer, Hypothenemus hampei (Ferrari, 1867) (Coleoptera: Curculionidae): A meta-analysis

Coffee berry borer pest (CBB) is one of the main pests that has a significant impact on coffee production and quality. In Indonesia, the utilization of plant-based pesticides has promising prospects in controlling CBB. The purpose of this study is to provide information on the impact of different types of plant pesticide on CBB mortality through a measurable algorithm analysis. A literature search was performed using Scopus, Web of Science, Google Scholar, Researchgate, and ScienceDirect. A linear mixed model (LMM) was applied to evaluate the effect of botanical pesticide application on the mortality rate of CBB. A total of 14 plant families were included in meta-regression analysis for estimating the effect size of each family. The average effect of pesticide exposure to CBB analyzed using LMM was 0.039 which mean that botanical pesticidal exposure has significant effect on the mortality rate of CBB (P<0.05). The results of this study suggested that the use of botanical insecticide especially derived from plants belonging to Family Anacardiaceae was significantly effective in controlling CBB.

Effectiveness of Citronella and Basil Essential Oil Spray as Repellents against Aedes aegypti Mosquitoes

Background: In 2023, Dengue Fever cases in Indonesia reached 35,694 cases from January to May. Dengue Fever is caused by the bite of Aedes aegypti mosquitoes. Mosquito control efforts have been widely conducted, including the use of chemical insecticides. The use of chemical insecticides can lead to environmental contamination and cause skin irritation. An alternative approach that can be taken is to use natural insecticides. One of the natural insecticides that can be used as a repellent is citronella and basil essential oils. Citronella and basil essential oils contain geraniol and citronellal, which can cause mortality in mosquitoes. This study intends to evaluate the effectiveness of a spray mixture of basil leaves and citronella essential oil as a mosquito repellent. Materials and Methods: Aedes aegypti mosquitoes, basil leaf essential oil, citronella essential oil, propylene glycol, glycerin, butylated hydroxytoluena and etanol 96% v/v. Subsequently, an evaluation of physical properties was conducted, including organoleptic testing, pH, and viscosity evaluation, as well as irritation and repellent activity test. Results: The spray formulations in the control and F1 are clear in color, while F2 and F3 are clear with a slightly yellowish hue. The scent produced has the characteristic smell of citronella. The pH and viscosity tests resulted in pH values consistent with the skin's pH range of 4.5-7 and viscosity within the range of 1-1000 Cp. The spray formulation did not irritate after 48 hours of observation. The results of the effectiveness test indicate that F2 can protect against mosquito bites for 1 hour, while F3 can protect for 3 hours. Conclusion: Citronella essential oil and basil leaves are effective as a repellent for the Aedes aegypti mosquito for 3 hours of use in concentration 15%.

Emulsion from the oil of the seed of Euterpe oleracea (açaí): study of activity and safety against Aedes aegypti

Euterpe oleracea is an oleaginous plant found in the Amazon, the oil from this seed is a promising raw material for various industries. Zika, Chikungunya and Dengue, whose vetora is the Aedes aegypti, are public health problems and their main form of control is the use of insecticides. The objetive was to carry out the physical-chemical characterization of the oil from the assai seed and to evaluate its activity in the face of the Aedes aegypti. Physico-chemical characterization, FTIR, thermal analysis and determination of fatty acids by CG of oil, larvicide activity and emulsion pupicide containing oil from the seed of E. oleracea front Aedes aegypti and acute toxicity of emulsion were performed. The physical and chemical parameters are within the expected range in the literature. The oil was thermally stable up to 304.48 °C, with a melting peak of 25.22 °C. The fatty acid profile averaged 72% unsaturated fatty acids. Infrared spectroscopy showed strains referring to the general structure of the triglyceride. Aedes aegypti larvicide and pupicidal activity were observed and was not considered toxic to mammals after the acute toxicity test.

Post-harvest Problems of Cowpeas Faced by Farmers in Madagali Local Government Area of Adamawa State, Nigeria

Post-harvest losses in cowpea have been a problem for cowpea farmers in Madagali Local Government Area. These losses are mainly due to insect pest attacks and spillage during post-harvest handling operations. To determine the post-harvest problems of cowpea. Five farming communities were selected, and twenty cowpea farmers from each community represented the entire population, resulting in a total of one hundred farmers. Structured questionnaires were used to collect data from the respondents. The questionnaires were scored using a 4-point Likert scale. The collected data were subjected to descriptive statistics using Microsoft Excel. According to the study, the majority of farmers asserted that steel drums were the best storage technique, with the highest mean score of 3.39, while rhomboidal storage techniques had the lowest mean score of 2.15 in the study area. Pests had the highest mean score of 3.12, which was considered the major problem in cowpea storage, while lack of knowledge about the storage facility had the lowest mean score of 1.94 and was considered a minor storage problem in the study area. However, the use of proper insecticides had the highest mean score of 3.32 and was considered the best method of pest control for cowpea in the study area, while the use of silos with a mean score of 2.16 was considered a less effective method for controlling pests in cowpea in the study area. Most farmers store their cowpea for five to six months to prevent pest damage.

Impact of pre-inoculation of soybean seeds with Bradyrhizobium spp. applied 60 days before sowing

The pre-inoculation of soybean seeds optimizes sowing process, enhancing biological nitrogen fixation, seed quality, and overall crop yield. This study aimed to evaluate the efficacy of pre-inoculating soybean seeds with the commercial inoculant Biofix Premium (Bradyrhizobium diazoefficiens SEMIA 5080 and Bradyrhizobium japonicum SEMIA 5079, 5x10^9 CFU/mL), along with a cell protector and chemical treatment. Four soybean trials were performed in Paraná, São Paulo, Minas Gerais, and Goiás states during the 2021/2022 agricultural year, utilizing a randomized complete block design with four treatments and six replications. The treatments were: 1- Control (no inoculation); 2- Fertilization with 200 kg.ha-1 of nitrogen; 3- Commercial standard seed inoculation (50 mL/50 kg of seeds) on the sowing day; 4- Seed inoculation with Biofix Premium (125 mL/100 kg of seeds), Protetor Ultra (0.5 mL/kg), Potenzial TS (0.2 mL/kg), and CoMo Platinum (100 mL/ha), applied 60 days before planting. Results showed that Biofix Premium applied 60 days before sowing, formed nodules and nodule mass similar to the comercial inoculant applied at sowing day. This led to a similar nitrogen fixation, chlorophyll content, shoot dry mass accumulation, grain yield, and nitrogen content compared to the comercial inoculant applied at sowing day. Yield gains with Biofix Premium ranged from 5-8% compared to the control (without inoculation), with no significant differences from the commercial seed inoculation applied on the sowing day. The use of insecticides and fungicides together with Biofix Premium, Protector Ultra, and Potenzial TS is recommended in the pre-inoculation of soybean seeds up to 60 days before sowing, without compromising plant nodulation and crop yield

Kdr mutations and deltamethrin resistance in house flies in Abu Dhabi, UAE

BackgroundThe house fly, Musca domestica, is a significant carrier of diseases that can impact public health. Repeated use of pyrethroid insecticides may act as a selection pressure for mutations and amino acid substitutions in the house fly voltage-sensitive sodium channel (VSSC), which ultimately confers resistance. The objectives of this study were to determine the presence of knockdown resistance (kdr) mutations using molecular tools and to set up a CDC bottle bioassay specific for house flies in the United Arab Emirates (UAE) to screen for deltamethrin resistance.MethodsAdult flies were collected from 19 locations in Abu Dhabi, UAE, and DNA was extracted, followed by PCR amplification of specific alleles (PASA) and conventional PCR using several primers to amplify regions of the VSSC gene. Sanger sequencing was performed on PCR products. We also designed primers that detect four kdr mutations using complementary DNA (cDNA) in reverse transcriptase (RT)-PCR followed by Sanger sequencing. Additionally, a CDC bottle bioassay was set up for detecting deltamethrin resistance in adult house flies.ResultsIn PASA, the primers successfully amplified the target bands (480, 280 and 200 bp). The kdr allele was found in flies collected from 18 of the 19 locations, at the highest and lowest prevalence of 46.9% and 9.4%, respectively. Resistant homozygous (RR) insects constituted 5.0% of the tested populations, and heterozygous (RS) insects accounted for 36.5%. The RR genotype was prevalent in house flies collected at 10 of 19 sampling locations. House fly populations were mostly in Hardy–Weinberg equilibrium, except in three locations. In addition to verifying the presence of the previously identified kdr mutation L1014F, in this study we detected two kdr mutations, L1014H and T929I, that have not previously been reported in the UAE. Also, for the first time in the UAE, a CDC bottle bioassay for deltamethrin resistance was used, which found that 60 min and 4.5 µg/ml were the diagnostic time and dose, respectively. Using this assay, we detected deltamethrin resistance in house flies from two of 16 locations, with a resistance level of 12.5%.ConclusionsUsing DNA sequencing, we confirmed the presence of a known kdr mutation and uncovered two new kdr mutations in house flies from Abu Dhabi. Additionally, we detected deltamethrin resistance in these flies using a CDC bottle bioassay. Further research is recommended to comprehensively identify more kdr mutations in UAE house fly populations and assess their impacts on control strategies.Graphical

Resistance of mosquitoes to Lambda-Cyhalothrin and DDT in a Niger Delta Region of Nigeria.

The escalation of insecticide resistance across the World Health Organization (WHO) African region calls for the routine monitoring of insecticide resistance in mosquitoes. While pyrethroids are recommended for use and dichlorodiphenyltrichloroethane (DDT) has been prescribed, it is imperative to reevaluate their efficacy across diverse geographical settings. The extent of resistance among mosquitoes to DDT and lambda-cyhalothrin remains understudied in Ika North East, Delta State, Nigeria, where the yellow fever virus was reported in 2019. We investigated the susceptibility of female mosquitoes to DDT (4%) and lambda-cyhalothrin (0.05%) in this specific study area. Adult female mosquitoes of Anopheles gambiae, Culex quinquefasciatus, and Aedes albopictus, aged between 2 and 4 days, were subjected to these insecticides utilizing the WHO bioassay method. The assessment of knockdown was done between 10 and 60 min, then mortality after 24 h. C. quinquefasciatus and A. albopictus mosquitoes exposed to DDT and lambda-cyhalothrin exhibited high susceptibility, resulting in complete mortality (100%); however, A. gambiae displayed resistance, with mortality rates of 19% and 76%, respectively . Notably, A. gambiae mosquitoes exposed to piperonyl butoxide (PBO)-DDT and PBO-lambda-cyhalothrin exhibited enhanced mortality, reaching 95% (indicating suspected resistance) and 100% (indicating susceptibility), respectively. Knockdown time (KDT) for 50% in mosquitoes exposed to lambda-cyhalothrin ranged from 3.94 to 33.51 min. Similarly, KDT model for 95% ranged from 19.04 to 84.15 min. Among the tested mosquito species, Culex mosquitoes exhibited the shortest knockdown resistance time for lambda-cyhalothrin, recorded at 3.94 min. Similarly, the KDT for DDT ranged from 24.97 to 187.06 min for 50% mortality and from 61.04 to 431.03 min for 95% mortality, respectively. Anopheles mosquitoes exposed to PBO + DDT recorded the lowest KDT. Our study underscores the potential of exercising caution in the use of DDT and lambda-cyhalothrin insecticides for the control of mosquitoes due to emerging resistance.

“Potential pathogens detection in Spodoptera frugiperda larvae maintained under laboratory conditions”

The microbiome of Spodoptera frugiperda plays a fundamental role during its biological cycle, since a great diversity of microorganisms interact through different mechanisms to maintain homeostasis. Their functions include, for example, defense against pathogens, degradation and the supply of functional molecules, among others. However, factors such as changes in diet, the use of insecticides, antibiotics, environmental factors, age or sex can interfere with the microbiome causing dysbiosis. Therefore, the objective of this work was to perform a metagenomic analysis of healthy and dead larvae with symptoms of infection to detect potential pathogenic agents. The results show that the genus Enterococcus presented an average relative abundance of 89.2% in healthy larvae and an average of 94.75% in dead larvae. The presence of Pseudomonas was also detected, with an average relative abundance of 10.8% in healthy larvae and 0.5% in dead larvae. While Acetobacter presented an average relative abundance in dead larvae of 4.5%. Interestingly, readings corresponding to viruses were 0.004% in healthy larvae and 1.48% in dead larvae, which were related to pathogenic viruses of the baculovirus family. The detection of potential pathogens that can affect S. frugiperda during rearing is of most importance to avoid their dispersal or affecting the colony.

MATHEMATICAL MODELING OF THE SPREAD OF VECTOR BORNE DISEASES WITH INFLUENCE OF VERTICAL TRANSMISSION AND PREVENTIVE STRATEGIES

This work is aimed at formulating a mathematical model of the spread of vector-borne diseases with influence of vertical transmission and preventive strategies. Vector borne diseases are caused by viruses, bacteria, and parasites typically conveyed by mosquitoes. Certain illnesses transmitted by vectors include West Nile Virus, Malaria, Zika virus, Dengue fever, Rift valley fever, and Viral encephalitis induced by pathogens like bacteria, viruses, and parasites. The positive solutions of the model are presented and the theory of basic reproduction number was used to study the model dynamical behaviour. When reduces; the diseases are wiped out of the population with time and vice versa. The disease free and endemic equilibria states of the model were determined and investigated to be locally and globally stable.We incorporated the use of Insecticide –Treated Nets (ITN), Indoor Residual Sprayings (IRS) and condom usage as preventive measures in the presence of treatment. Numerical simulations show that complete intervention measures, that is, the use of ITN, IRS and condom usage while placing the infected on treatment have valuable impact on the spread of vector-borne diseases.

Rearing Neoseiulus cucumeris and Amblyseius swirskii (Mesostigmata: Phytoseiidae) on non-target species reduces their predation efficacy on target species

Abstract In Florida, strawberries are prone to infestation by Tetranychus urticae Koch (twospotted spider mite; Trombidiformes: Tetranychidae) and Scirtothrips dorsalis Hood (chilli thrips; Thysanoptera: Thripidae). Management of these pests using conventional insecticides is becoming difficult, thereby forcing many growers to adopt the use of commercially available biological control agents including Neoseiulus cucumeris Oudemans and Amblyseius swirskii Athias-Henriot (both Mesostigmata: Phytoseiidae). These predators are mass reared on prey different from T. urticae, and their prey switching capacity is unknown. Therefore, the objective of this study was to compare the predation capacity of A. swirskii and N. cucumeris feeding on familiar and unfamiliar prey. Thus, using T. urticae as a non-familiar prey model organism, a no choice test was conducted where A. swirskii and N. cucumeris were each provided with Acarus spp. (commonly used as prey for commercial rearing of predatory mites) as familiar prey and eggs, deutonymphs, and adult females of T. urticae as unfamiliar prey. Prey consumption was recorded at 12, 24, 36 and 48 h. Our results show that both A. swirskii and N. cucumeris exhibited higher prey consumption when prey was familiar (Acarus spp.) compared to unfamiliar prey. Additionally, both predators showed higher consumption of eggs compared to T. urticae nymphs and adults. In 12 h, both predators had consumed 50 % of eggs, however, 36–48 h were required for 50 % of the T. urticae adults and nymphs to be consumed. Therefore, strawberry growers utilizing these predatory mites ought to refrain from the use of insecticides known to be detrimental to predatory mites for a period of at least 48 h to allow the predators to adjust to the new prey and environment.

Exploring biocidal effects of methyl salicylate and limonene toward <em>Trogoderma granarium</em> Everts

The khapra beetle, Trogoderma granarium, poses a significant threat as a post-harvest pest in stored products and stands out as a crucial quarantine concern globally. Unlike many other stored product pests, this species proved challenging to manage using conventional insecticides and alternative non-chemical methods. The exploration of plant-based natural products, particularly essential oils, as alternatives arises in response to challenges associated with the prolonged use of synthetic insecticides. While essential oils show promising activity, their use encounters challenges associated with standardization. This study investigates the feasibility of employing some single chemical compounds widespread in several essential oils with insecticidal activity as candidate insecticides, specifically limonene and methyl salicylate in contact/fumigation bioassays toward T. granarium adults. The results showed that methyl salicylate caused a lethal time of 50% (LT50) at the dose of 1 mg after 7.40 hours of exposure. The LT50 calculated for limonene was 86.83 hours while positive control using deltamethrin, used at the recommended dose of the manufacturer, was 5.20 hours after exposure. These data suggest that methyl salicylate can be exploited as a candidate for further tests in field conditions toward T. granarium also in consideration of its relative low toxicity for humans.

Patterns of insecticide uses and its impact on the health of the farmers in Tangail district of Bangladesh

Appropriate and judicious application of insecticide is the most effective measure of crop protection against the injury and damage of insect pests. However, the tendency of the farmers is to apply insecticide without maintaining proper dose, time and precautionary measures. This study was conducted in Dhanbari and Madhupur upazilas of the Tangail district during July to October 2020 to find out the patterns of insecticide use on summer vegetables and the potential risks of insecticides on the health of farmers. Data were collected from randomly selected 120 farmers through a pre-tested questionnaire. The majority of farmers within the study area obtained information regarding specific insect pests and the recommended insecticide from local retailer shops 81.7%), whereas information on insecticide dosage was primarily gathered from experts (91.7%). In the study area, farmers applied insecticides once/twice a season (66.7%). The survey report showed that 60.0% of the farmers applied insecticides without reading the label information, while all the farmers applied insecticides using hand driven sprayer machine between the hours of 10 am to 3 pm. Results revealed that 63.3% of the farmers took a moderate protective measures, but 93.3% did not consider pre-harvest Interval (PHI). A considerable portion of farmers (48.3%) kept pesticide bottles and packaging alongside other inputs, while most respondents (96.6%) disposed of these items in the fields. It was found that 70.0% of the farmers were acquainted with health hazards, 56.6% knew about water pollution, 54.1% knew about reduction of pollinators due to insecticide application. Based on the perspectives of the participants, it was also found that, 60.0% farmers suffered from physical weakness, 55.0% suffered in loss of appetite, 38.3% suffered in eye irritation, 28.3% experienced in body itching, and 12.7% suffered urinary and sexual disorder. Ann. Bangladesh Agric. (2023) 27 (1): 31-39

Metabolomic Approaches in Assessing the Insecticidal Activity of the Extracts from Argemone ochroleuca Sweet (Papaveraceae) Against Three Diverse Crop Pests of Economic Importance.

For years, crop protection from pest attack, has been dominated by the use of synthetic insecticides. However, many of them can cause severe environmental problems and human health. In this context, the use of plant extracts constitutes an alternative to avoid this kind of contaminants. In this work, we investigated the chemical constituents and insecticidal activity of different extracts of leaves and stems of Argemone ochroleuca Sweet (Papaveraceae) against three economically important pests Sitophilos zeamais (Coleoptera:Curculionidae), Galleria mellonella (Lepidoptera:Pyralidae) and Xyleborus ferrugineus (Coleoptera:Scolytidae). A GC-MS analysis mostly revealed the presence benzylisoquinoline alkaloids such as allocryptopine, protopine, among others. For the insecticidal activity, after nine hours of contact, the methanolic leaves extract showed a 100 % of mortality, followed by the dichloromethane stems extract with up to 93 % of mortality. The results suggest that the benzylisoquinoline alkaloids are involved in the insecticidal activity through the octopaminergic system of the tested insects.

Defense Responses of Different Rice Varieties Affect Growth Performance and Food Utilization of Cnaphalocrocis medinalis Larvae

Rice leaf folder, Cnaphalocrocis medinalis (Guenée), is one of the most serious pests on rice. At present, chemical control is the main method for controlling this pest. However, the indiscriminate use of chemical insecticides has non-target effects and may cause environmental pollution. Besides, leaf curling behavior by C. medinalis may indirectly reduce the efficacy of chemical spray. Therefore, it is crucial to cultivate efficient rice varieties resistant to this pest. Previous studies have found that three different rice varieties, Zhongzao39 (ZZ39), Xiushui134 (XS134), and Yongyou1540 (YY1540), had varying degrees of infestation by C. medinalis. However, it is currently unclear whether the reason for this difference is related to the difference in defense ability of the three rice varieties against the infestation of C. medinalis. To explore this issue, the current study investigated the effects of three rice varieties on the growth performance and food utilization capability of the 4th instar C. medinalis. Further, it elucidated the differences in defense responses among different rice varieties based on the differences in leaf physiological and biochemical indicators and their impact on population occurrence. The results showed that the larval survival rate was the lowest, and the development period was significantly prolonged after feeding on YY1540. This was not related to the differences in leaf wax, pigments, and nutritional components among the three rice varieties nor to the feeding preferences of the larvae. The rate of superoxide anion production, hydrogen peroxide content, and the activity of three protective enzymes were negatively correlated with larval survival rate, and they all showed the highest in YY1540 leaves. Compared to other tested varieties, although the larvae feeding on YY1540 had higher conversion efficiency of ingested food and lower relative consumption rate, their relative growth was faster, indicating stronger food utilization capability. However, they had a lower accumulation of protein. This suggests that different rice varieties had different levels of oxidative stress after infestation by C. medinalis. The defense response of YY1540 was more intense, which was not conducive to the development of the larvae population. These results will provide new insights into the interaction mechanism between different rice varieties and C. medinalis and provide a theoretical basis for cultivating rice varieties resistant to this pest.

Reducing pest pressure and insecticide use by increasing hedgerows in the landscape

Reducing pesticide use while maintaining agricultural production is a key challenge. Ecological theory predicts that landscape simplification is likely to increase insect pest outbreaks and limit their control by natural enemies, and this situation could boost insecticide use. Some studies have indeed detected that simpler landscapes were associated with higher insecticide use, but very few have demonstrated that this association is caused by landscape effects on pest abundance. Here, we analysed insecticide use and pest pressure in response to landscape simplification across 557 arable farms across France. Accounting for potentially confounding covariates, we found that lower cover of hedgerows in the landscape, but not semi natural areas, were associated with higher on-farm insecticide use. We also found that greater hedgerow coverage was associated with lower aphid pest pressure. Specifically, increasing the landscape-scale cover of hedgerows from 1 % to 3 % meant that insecticide use was halved. These findings suggest that restoring hedgerow cover at the landscape scale should be targeted in order to speed-up the ecological intensification of agriculture.