Use Of Insecticides In Agriculture Research Articles

Synthesis of novel direct Z-scheme heterojunction photocatalyst from WO3 nanoplates and SrTiO3 nanoparticles with abundant oxygen vacancies

Excessive use of insecticides in agriculture has raised a global concern owing to their environmental pollution. Various techniques are utilized for removal these compounds which one of the most efficient methods is photocatalytic degradation by heterojunction nanocomposites. Herein, a direct Z-scheme heterojunction nanocomposite with abundant oxygen vacancy defects was fabricated via simple hydrothermal treatment of WO3 nanoplate and SrTiO3 nanoparticle and was utilized as a powerful photocatalyst for decomposition of nitenpyram insecticide under illumination of simulated sunlight. The findings revealed that, the heterojunction nanocomposite with 30wt% of SrTiO3 has the best photocatalytic efficiency. Improvement of the photocatalytic ability may be ascribed to the existence of oxygen vacancy defects in heterojunction interfaces between two semiconductors, facilitating of charge carriers separation, and effective generation of the •O2− and •OH radicals. Furthermore, from the results of the radical capture studies, ESR techniques, and Mott-Schottky analyses, it can be concluded that the hydroxyl radical is the major oxidant for degradation of nitenpyram, and by modulating the charge carrier dynamics and regulation of the charge transfer pathways, a direct Z-scheme heterojunction nanocomposite is formed with improved photocatalytic efficiency. Additionally, the possible decomposition intermediates of nitenpyram were detected from the HPLC-MS analysis.

Agricultural Use of Insecticides Alters Homeostatic Behaviors and Cognitive Ability in Lymnaea stagnalis.

Lymnaea stagnalis is an ecologically important, stress-sensitive, freshwater mollusk that is at risk for exposure to insecticides via agricultural practices. We provide insight into the impact insecticides have on L. stagnalis by comparing specific behaviors including feeding, locomotion, shell regeneration, and cognition between snails collected at two different sites: one contaminated by insecticides and one not. We hypothesized that each of the behaviors would be altered in the insecticide-exposed snails and that similar alterations would be induced when control snails were exposed to the contaminated environment. We found no significant differences in locomotion, feeding, and shell regeneration of insecticide-exposed L. stagnalis compared with nonexposed individuals. Significant changes in feeding and shell repair were observed in nonexposed snails inhabiting insecticide-contaminated pond water. Most importantly, snails maintained and trained in insecticide-contaminated pond water did not form configural learning, but this cognitive deficit was reversed when these snails were maintained in insecticide-free pond water. Our findings conclude that insecticides have a primarily negative impact on this higher form of cognition in L. stagnalis. Environ Toxicol Chem 2023;00:1-12. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Phenotypic resistance to pyrethroid associated to metabolic mechanism in Vgsc-L995F-resistant Anopheles gambiae malaria mosquitoes.

Background: The indiscriminate use of insecticides in agriculture and public health lead to a selection of resistance mechanisms in malaria vectors compromising vector control tools and strategies. This study investigated the metabolic response in the Vgsc-L995F Anopheles gambiae Tiassalé resistance strain after long-term exposure of larvae and adults to deltamethrin insecticide. Methods: Vgsc-L995F An. gambiae Tiassalé strain larvae were exposed over 20 generations to deltamethrin (LS) and adults to PermaNet 2.0 (AS) and combining exposure at larvae and adult stages (LAS) and compared to unexposed (NS) group. All four groups were subjected to the standard World Health Organization (WHO) susceptibility tube tests using deltamethrin (0.05%), bendiocarb (0.1%) and malathion (5%). Vgsc-L995F/S knockdown-resistance ( kdr) mutation frequency was screened using multiplex assays based on Taqman real-time polymerase chain reaction (PCR) method. Additionally, expression levels of detoxification enzymes associated to pyrethroid resistance, including CYP4G16, CYP6M2, CYP6P1, CYP6P3, CYP6P4, CYP6Z1 and CYP9K1, and glutathione S-transferase GSTe2 were measured. Results: Our results indicated that deltamethrin resistance was a response to insecticide selection pressure in LS, AS and LAS groups, while susceptibility was observed in NS group. The vectors showed varied mortality rates with bendiocarb and full susceptibility to malathion throughout the selection with LS, AS and LAS groups. Vgsc-L995F mutation stayed at high allelic frequency level in all groups with a frequency between 87% and 100%. Among the overexpressed genes, CYP6P4 gene was the most overexpressed in LS, AS and LAS groups. Conclusion: Long-term exposure of larvae and adults of Vgsc-L995F resistant- An. gambiae Tiassalé strain to deltamethrin and PermaNet 2.0 net induced resistance to deltamethrin under a significant effect of cytochromes P450 detoxification enzymes. These outcomes highlight the necessity of investigating metabolic resistance mechanisms in the target population and not solely kdr resistance mechanisms prior the implementation of vector control strategies for a better impact.

Genomic-proteomic analysis of a novel Bacillus thuringiensis strain: toxicity against two lepidopteran pests, abundance of Cry1Ac5 toxin, and presence of InhA1 virulence factor.

Bacillus thuringiensis (Bt) is a biological alternative to the indiscriminate use of chemical insecticides in agriculture. Due to resistance development on insect pests to Bt crops, isolating novel Bt strains is a strategy for screening new pesticidal proteins or strains containing toxin profile variety that can delay resistance. Besides, the combined genomic and proteomic approaches allow identifying pesticidal proteins and virulence factors accurately. Here, the genome of a novel Bt strain (Bt TOL651) was sequenced, and the proteins from the spore-crystal mixture were identified by proteomic analysis. Toxicity bioassays with the spore-crystal mixture against larvae of Diatraea saccharalis and Anticarsia gemmatalis, key pests of sugarcane and soybean, respectively, were performed. The toxicity of Bt TOL651 varies with the insect; A. gemmatalis (LC50 = 1.45ngcm-2) is more susceptible than D. saccharalis (LC50 = 73.77ngcm-2). Phylogenetic analysis of the gyrB gene indicates that TOL651 is related to Bt kenyae strains. The genomic analysis revealed the presence of cry1Aa18, cry1Ac5, cry1Ia44, and cry2Aa9 pesticidal genes. Virulence factor genes such as phospholipases (plcA, piplc), metalloproteases (inhA), hemolysins (cytK, hlyIII, hblA, hblC, hblD), and enterotoxins (nheA, nheB, nheC) were also identified. The combined use of the genomic and proteomic data indicated the expression of Cry1Aa18, Cry1Ac5, and Cry2Aa9 proteins, with Cry1Ac5 being the most abundant. InhA1 also was expressed and may contribute to Bt TOL651 pathogenicity. These results provide Bt TOL651 as a new tool for the biocontrol of lepidopteran pests.

Phenotypic resistance to pyrethroid associated to metabolic mechanism in Vgsc-L995F-resistant Anopheles gambiae malaria mosquitoes

Background: The indiscriminate use of insecticides in agriculture and public health lead to a selection of resistance mechanisms in malaria vectors compromising vector control tools and strategies. This study investigated the metabolic response in the Vgsc-L995F Anopheles gambiae Tiassalé resistance strain after long-term exposure of larvae and adults to deltamethrin insecticide. Methods: We exposed, over 20 generations, Vgsc-L995F An. gambiae Tiassalé strain larvae to deltamethrin (LS) and adults to PermaNet 2.0 (AS) and combining exposure at larvae and adult stages (LAS) and compared to unexposed (NS) group. All four groups were subjected to the standard World Health Organization (WHO) susceptibility tube tests using deltamethrin (0.05%), bendiocarb (0.1%) and malathion (5%). Vgsc-L995F/S knockdown-resistance (kdr) mutation frequency was screened using multiplex assays based on Taqman real-time polymerase chain reaction (PCR) method. Additionally, expression levels of detoxification enzymes associated to pyrethroid resistance, including CYP4G16, CYP6M2, CYP6P1, CYP6P3, CYP6P4, CYP6Z1 and CYP9K1, and glutathione S-transferase GSTe2 were measured. Results: Our results indicated that deltamethrin resistance was a response to insecticide selection pressure in LS, AS and LAS groups, while susceptibility was observed in NS group. The vectors showed varied mortality rates with bendiocarb and full susceptibility to malathion throughout the selection with LS, AS and LAS groups. Vgsc-L995F mutation stayed at high allelic frequency level in all groups with a frequency between 87% and 100%. Among the overexpressed genes, CYP6P4 gene was the most overexpressed in LS, AS and LAS groups. Conclusion: Long-term exposure of larvae and adults of Vgsc-L995F resistant-An. gambiae Tiassalé strain to deltamethrin and PermaNet 2.0 net induced resistance to deltamethrin under a significant effect of cytochromes P450 detoxification enzymes. These outcomes highlight the necessity of investigating metabolic resistance mechanisms in the target population and not solely kdr resistance mechanisms prior the implementation of vector control strategies for a better impact.

A Modeling Approach for Assessing Ecological Risks of Neonicotinoid Insecticides from Emission to Nontarget Organisms: A Case Study of Cotton Plant.

The use of neonicotinoid insecticides in agriculture has posed threats to ecological systems, and there is a need to assess the ecological risks of neonicotinoids from emission to nontarget organisms. We introduced a modeling approach to assess the ecological risks of neonicotinoids using honeybee and earthworm as model organisms, and the simulation was flexible under different environmental conditions. Using the cotton plant as an example, the simulation results demonstrated that under current recommended application rates, the use of common neonicotinoid insecticides posed no threat to earthworms, with the simulated risk quotients (RQs) much lower than 1. However, the simulation for some neonicotinoid insecticides (e.g., acetamiprid) indicated that using these insecticides on cotton plants could threaten honeybees, with simulated RQs higher than 1. The variability analysis showed that in high-latitude regions, the unacceptable risk to honeybees posed by insecticide application can be further elevated due to cold, wet weather that results in relatively high insecticide levels in pollen and nectar. The model evaluation showed large overlaps of simulated risk intervals between the proposed and existing (BeeREX) models. Because the proposed and existing models have different simulation mechanisms, we recommend that these two models be used together to complement each other in future studies. Environ Toxicol Chem 2023;42:928-938. © 2023 SETAC.

Haematological alterations in a fresh water fish Anabas testudineus under cypermethrin exposure

Cypermethrin, a synthetic pyrethroid is a broad spectrum insecticide used extensively in households and agriculture fields to control the pests. Use of insecticides in agriculture to prevent the crop damage from pests come with a significant cost as they reach to the aquatic systems through irrigation and rain and deteriorates the water quality. It adversely affects the non-target organisms including fishes of the fresh water ecosystem. Pyrethroid insecticide cypermethrin was used for this investigation to study the alterations in blood biochemical of a fresh water fish Anabas testudineus. Acute toxicity of cypermethrin to the fish was determined for 24, 48, 72 and 96 hours. The LC50 value was measured 0.15 ppm, 0.20 ppm, 0.2 ppm and 0.30 ppm respectively by the regression equation. The sublethal concentration determined was 0.106 ppm. After exposure period of 30 days significant changes in the blood biochemical level was reported during the present study. Blood glucose, serum protein and serum cholesterol of cypermethrin treated fish exhibited hyperglycaemic, hypoproteinemic and hypercholesterolemic response. The present investigation come to a conclusion that cypermethrin alters the blood biochemistry of Anabas testudineus and hence, affects the fish health.

Antifeedant and larvicidal activity of bioactive compounds isolated from entomopathogenic fungi Penicillium sp. for the control of agricultural and medically important insect pest (Spodoptera litura and Culex quinquefasciatus)

The use of chemical insecticides in agriculture has posed several challenges to environment and ecosystem health. Pesticides of biological origin are considered to be suitable for sustainable environment. In the present study bioactive compounds from Penicillium sp. was isolated and tested for insecticidal activity on Spodoptera litura and Culex quinquefasciatus larvae. Ethyl acetate extract of Penicillium sp. were characterized using GC–MS and FT-IR analysis. GC–MS analysis showed 20 different bioactive compounds namely, Propanoic acid, ethyl ester, Acetic Acid, Propyl Ester, Isopentyl Acetate, Acetic Acid, 2-Methylpropyl Ester, Behenic alcohol, 1-Hexadecene, 1-Octadecene, 1-Hexacosanol, n-Hexadecanoic acid, 1-Tetradecanol, 1-Dodecene, Tetrydamine, and Octadecanoic acid. The presence of functional groups such as, chloroalkanes, sulfonates, phosphines, amines, carboxylic acid, alkanes, and isocyanates was identified by using FTIR. Ethyl acetate extract of Penicillium sp., were tested for larvicidal activity on Spodoptera litura and Culex quinquefasciatus larvae showed significant larval mortality after 48 h of exposure with LC50: 72.205 mg/ml: LC90: 282.783 mg/ml and LC50: 94.701 mg/ml: LC90:475.049 mg/ml respectively. High antifeedant activity was observed in 300 μg/ml at 48 h of crude extract exposure. The present study concludes that Penicillium sp., secondary metabolites are effective for control of Spodoptera litura and Culex quinquefasciatus larvae.

Fitness cost of malathion resistance in Egyptian Culex pipiens populations.

The extensive use of insecticides in agriculture and public health has resulted in the rapid development of insecticide resistance in mosquito populations. Therefore, in this study, we aimed to evaluate insecticide resistance costs on the fitness of Culex pipiens. Two Cx. pipiens field populations (Beheira malathion-resistant and Gharbia malathion-susceptible) were compared to the reference (sensitive) population. The biochemical composition and expression of four genes relevant to insecticide resistance were estimated in third instar larvae. Adult survival, female fecundity and egg hatchability were also determined. As per our findings, it was found that the total protein and carbohydrate contents in Beheira malathion-resistant larvae were significantly lower than that in the reference larvae. Beheira malathion-resistant larvae had higher phenoloxidase (PO) specific activity than the reference population. In terms of the relevant genes, only cytochrome P450 (CYP6F1) expression showed elevated levels in the Gharbia malathion-susceptible population compared to the Beheira malathion-resistant population. In esterases (Estα and Estβ) and glutathione S-transferase, the tested populations did not show any significant differences. Compared to the reference mosquito population, Gharbia malathion-susceptible Cx. pipiens males exhibited significantly longer median survival. Female fecundity and hatchability showed nonsignificant differences among the populations tested. In conclusion, malathion resistance can induce lower protein and carbohydrate contents, but higher PO activity in larvae.

Insecticidal Effect of Pistacia lentiscus (Anacardiaceae) Metabolites against Lobesia botrana (Lepidoptera: Tortricidae)

The extensive use of synthetic insecticides in agriculture poses a great risk for human health and the ecosystem, and mandates the development of safer alternatives derived from natural products. In the present study, we assessed the larvicidal effect of Pistacia lentiscus fruits, leaves, and bark extracts and their components on larvae of a major vine pest, Lobesia botrana. Pistacia lentiscus is an evergreen shrub or small tree possessing significant medicinal value with numerous therapeutic uses since antiquity. Using petri dish residual exposure and topical application bioassays we demonstrated that the fruit extract of P. lentiscus and its metabolites were toxic on L. botrana larvae. Extracts from leaves and bark showed no effect. Βioassay-guided fractionation of P. lentiscus fruit hexane extract led to the identification of its constituents with insecticidal properties on L. botrana larvae. Specifically, we have identified that the main contributor to the bioactivity of the hexane extract of P. lentiscus fruits is its major fraction, PLFHe2 (76.25%). Furthermore, we have found that PLFHe2 is a mixture of triglycerides and that the fatty acids responsible for the observed toxicity are oleic and linoleic acid.

Pengaruh Insektisida Klorpirifos Terhadap Struktur Histologi Intestinum Ikan Wader Pari (Rasbora lateristriata Bleeker, 1854)

Chlorpyrifos is one of commonly used insecticides. However, the use of insecticides in agriculture has negative impacts including lethal effect to non-target organisms. Wader pari fish is a type of freshwater fish that lives in rice fields or rivers and can be used as an indicator of water pollution. The purpose of this study was to determine the intestinal histological structure, the histopathological effect of chlorpyrifos on intestine, and population number of goblet cells, respectively. The treatment concentration of 0.001; 0.005; and 0.01 ppm were determined by preliminary trial and exposed for 168 hours. Fish behavior and water quality were monitored. The fish were still alive until the last day of exposure were then made intestinal histological preparations using the paraffin method and staining with Haematoxylin Eosin (HE), Mallory Acid Fuchsin (MAF), Periodic Acid Schiff (PAS). The results showed that the histological structure of the wader pari intestine consisted of mucosal tunica, submucosal tunica, muscularis tunica, and serous tunica. Furthermore, chlorpyrifos has a significant effect on population number of goblet cells. The intestine damages were edema, vacuolization, cloudy swelling, hemorrhage, lysis, and fusion of vili. It could be concluded that chlorpyrifos caused intestinal damage in wader pari fish.

Ecotoxicological Studies on the Action of Actara 25 WG Insecticide on Prussian Carp (Carassius gibelio) and Marsh Frog (Pelophylax ridibundus).

The toxic action of the Actara 25 WG insecticide (it contains 25% thiamethoxam as an active substance) in non-lethal doses was studied in two species of aquatic organisms—the Prussian carp (Carassius gibelio) and the marsh frog (Pelophylax ridibundus)—at two thermal levels, 6–8 °C (low temperature) and 18–20 °C (room temperature), respectively. In the Prussian carp, we recorded decreases in oxygen consumption and stimulation of the respiratory rhythm, changes that were more pronounced in the case of intoxicated fish and when the species were kept at room temperature. The histopathology of the lung in the frog illustrated the thickening of the conjunctival septum, an increase in the number of mucous cells, and an increase in the ratio between the diameter of the nucleus and the diameter of the pneumocyte. All of these changes were more pronounced in the animals kept at higher temperature. Our study looks at the extent to which temperature changes can influence the ability of poikilothermic organisms to withstand the presence of toxic substances in the environment as a result of the impact of the use of insecticides in agriculture. The two tested organisms are a common presence for the study area, which was affected in the last decade by climate change.

Historical samples reveal a combined role of agriculture and public-health applications in vector resistance to insecticides.

BACKGROUNDInsecticide resistance is the major threat to vector control and for the prevention of vector‐borne diseases. Because almost all insecticides used against insect vectors are or have been used in agriculture, a connection between agricultural insecticide use and resistance in insect vectors has been hypothesized. However, it is challenging to find a causal link between past agricultural use of insecticides and current resistance in vector populations without historical data series. Here we investigated the relative contribution across time of agricultural and public‐health insecticide applications in selecting for diflubenzuron (DFB) resistance in Culex pipiens populations. Using DNA sequencing, we looked for DFB resistant mutations in current and historical mosquito samples, dating back to the 1980s–1990s, when DFB was used in agriculture but not yet in mosquito control.RESULTSIn the samples collected before the introduction of DFB in vector control, we found the resistant mutation I1043M in rural regions but not any of the neighboring urban and natural areas, indicating that the selection pressure was derived by agriculture. However, after the introduction of DFB for vector control, the resistant mutations were found across all study areas showing that the initial selection from agriculture was further boosted by the selection pressure imposed by the mosquito control applications in the 2000s.CONCLUSIONSOur findings support a combined role of agricultural and public‐health use of insecticides in vector resistance across time and call for specific actions in integrated resistance management, including increased communication between agriculture and health practitioners. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Contributions of nearby agricultural insecticide applications to indoor residential exposures

BACKGROUND AND AIM: Pesticide exposure has been associated with adverse health effects; individuals may be exposed to pesticide drift from nearby agricultural fields. We evaluated relationships between agricultural insecticide applications and insecticide levels in carpet dust. METHODS: We measured concentrations (ng/g) of allethrin, azinphos-methyl, carbaryl, chlorpyrifos, cyfluthrin, cypermethrin, deltamethrin, diazinon, malathion, permethrin, phosmet, propoxur, tetramethrin in carpet-dust samples collected from 558 California homes. After using the California Pesticide Use Reporting database (reporting unit: ~2.59km2) to estimate agricultural insecticide use within buffers with radii of 0.5-, 1-, 2-, 3-, and 4km around each home, we calculated the density of use (kg/km2) during 30-, 60-, 180-, and 365-day periods prior to dust collection and evaluated relationships between insecticide density and concentrations in dust. We modeled natural-log transformed dust concentrations using Tobit regression for insecticides with 40% detection. For insecticides detected ≤40%, odds of detection were modeled with logistic regression. Models were adjusted for season, year, occupation, and home/garden uses. RESULTS:Detection frequencies ranged from 10% for allethrin, azinphos-methyl, and malathion to 80% for diazinon, chlorpyrifos, and permethrin. Chlorpyrifos applications within 1-4km of the residence during all time periods were associated with higher dust concentrations compared to homes without nearby applications. Carbaryl applications within 2-4km of homes 30- and 60-days prior to dust collection were associated with higher concentrations (30-days/2km, β any applications vs. none=8.2, 95%CI 1.8-37.6; 60-days/4km, β median density vs. none=4.2, 95%CI 1.1-15.7). Cyfluthrin and phosmet applications 180- and 365-days prior to dust collection were associated with higher odds of detection (365-days/4km, highest density vs. none: OR=2.2, 95%CI 1.2-4.0 and 6.2, 95%CI 3.3-12.0, respectively) compared to homes with no nearby use. CONCLUSIONS:Agricultural insecticide use within 4km of a home could be an important determinant of indoor contamination. Our findings provide valuable information for the development of exposure metrics for epidemiologic health studies. KEYWORDS: Pesticides, Exposures, Exposure assessment, Environmental epidemiology, Children's environmental health

Use of Insecticides in Agriculture and the Prevention of Vector-Borne Diseases: Population Knowledge, Attitudes, Practices and Beliefs in Elibou, South Côte d'Ivoire.

People’s knowledge, attitudes, practices and beliefs (KAPB) pertaining to malaria are generally well described. However, little is known about population knowledge and awareness of insecticide resistance in malaria vectors. The aim of this study was to investigate KAPB related to insecticide resistance in malaria vectors due to the use of insecticides in agriculture and the prevention against mosquitoes. In mid-2017, we carried out a cross-sectional survey in Elibou, South Côte d’Ivoire, employing a mixed methods approach. Quantitative data were obtained with a questionnaire addressed to household heads. Interviews were conducted with key opinion leaders, including village chiefs, traditional healers, heads of health centres and pesticide sellers. Focus group discussions were conducted with youth and elders. A total of 203 individuals participated in the questionnaire survey (132 males, 65%). We found that people had good knowledge about malaria and mosquitoes transmitting the disease, while they felt that preventing measures were ineffective. Pesticides were intensively used by farmers, mainly during the rainy season. Among the pesticides used, insecticides and herbicides were most commonly used. While there was poor knowledge about resistance, the interviewees stated that insecticides were not killing the mosquitoes anymore. The main reason given was that insecticides were diluted by the manufacturers as a marketing strategy to sell larger quantities. More than a third of the farmers used agricultural pesticides for domestic purposes to kill weeds or mosquitoes. We observed a misuse of pesticides among farmers, explained by the lack of specific training. In the community, long-lasting insecticidal nets were the most common preventive measure against malaria, followed by mosquito coils and insecticide sprays. The interviewees felt that the most effective way of dealing with insecticide resistance was to combine at least two preventive measures. In conclusion, population attitudes and practices related to insecticides used in agriculture and the prevention against mosquitoes could lead to resistance in malaria vectors, while people’s knowledge about insecticide resistance was limited. There is a need to raise awareness in communities about the presence of resistance in malaria vectors and to involve them in resistance management.

Kenneth Mellanby Commander of the Order of the British Empire (CBE) (1908–1993). The facts about scabies

Kenneth Mellanby was a distinguished biologist specialising in entomology. He helped to establish the first university in Nigeria and undertook pioneering work on the use of insecticides in agriculture. However, he will best be remembered for a series of experiments which he undertook on human volunteers during the Second World War. These experiments established the mechanism of transmission of scabies and allowed its effective control at a time when the condition had reached epidemic proportions, causing a significant adverse effect on public morale and military effectiveness. Mellanby's wartime monograph on scabies remains to this day the definitive work on the disease and is still studied by dermatologists. His subsequent book Human Guinea Pigs is a remarkable account of the privations to which wartime volunteers willingly submitted themselves in a way that would have never passed any current medical ethics committee.

Insecticide Risk in US Surface Waters: Drivers and Spatiotemporal Modeling

Although pesticide contamination in agricultural surface waters is a common phenomenon, large-scale studies dealing with the responsible drivers are rare. We used data from 259 publications reporting 5830 individual water or sediment concentrations of 32 insecticides and their metabolites in 644 US surface waters to determine the factors driving insecticide risks, that is, exceedance of regulatory threshold levels (RTLs). Multiple linear regressions (R2 adj. = 49.6-76.5) revealed that toxicity-normalized agricultural insecticide use (i.e. use divided by toxicity) was the most important driver. Burst rainfall erosivity and irrigation practices also had risk-promoting effects, whereas time, catchment size, and sampling interval had risk-demoting effects. A regression model (R2 adj. = 62.2, n = 1833) for small, medium, and large running waters was validated and used for risk mapping at the national scale, highlighting multiple regions, where the comparison of predicted insecticide concentrations with their RTLs indicate adverse conditions for aquatic organisms. Particularly in smaller streams, risks were most pronounced with an average RTL exceedance frequency of 27.7% in all grid cells (n = 9968). Finally, mixture toxicity was mainly (about 76.7%) explained by the most toxic compound in the mixture, causing ∼95.7% of RTL exceedances. Identifying the factors, which drive exposure for all relevant insecticide classes, and subsequently mapping these risks for surface waters of various sizes across the U.S., will support future risk management.

Evidence of insecticide resistance selection in wild Anopheles coluzzii mosquitoes due to agricultural pesticide use

BackgroundThe wetlands used for some agricultural activities constitute productive breeding sites for many mosquito species. Thus, the agricultural use of insecticide targeting other pests may select for insecticide resistance in malaria mosquitoes. The purpose of this study is to clarify some knowledge gaps on the role of agrochemicals in the development of insecticide resistance in malaria vectors is of utmost importance for vector control.MethodsUsing the CDC bottle test and the log-probit analysis, we investigated for the first time the resistance levels of Anopheles coluzzii mosquitoes to neonicotinoids, insecticides used exclusively for crop protection in Côte d’Ivoire. The study was conducted in two agricultural regions (Tiassale and Gagnoa) and one non-agricultural region (Vitre) between June and August 2017 using clothianidin, acetamiprid and imidacloprid.ResultsMosquito populations from Tiassale and Gagnoa (agricultural settings) were determined to be resistant to acetamiprid with mortality rates being < 85% at 24 h post-exposure. In Vitre (non-agricultural area) however, the mosquito population was susceptible to acetamiprid. In all three localities, mosquito populations were resistant to imidacloprid (mortality rates were 60% in Vitre, 37% in Tiassale, and 13% in Gagnoa) and completely susceptible to clothianidin (100% mortality). An. coluzzii represented 100% of mosquito collected in Gagnoa, 86% in Tiassale and 96% in Vitre.ConclusionsThis study provides strong evidence that agricultural use of insecticides can cause insecticide resistance in malaria vector populations. Insecticide resistance driven by agrochemical usage should be considered when vector control strategies are developed.

Elevated CO2, chlorpyrifos and biochar influence nitrification and microbial abundance in the rhizosphere of wheat cultivated in a tropical vertisol

Climate change is predicted to increase pest infestation and may lead to high use of insecticides in agriculture. Elevated CO2 and other climate factors affect soil microbial processes like nitrification. To regulate climate change biochar (BC) has been recommended for soil application. It is hypothesized that elevated CO2 and biochar may stimulate autolithotrophic nitrifiers and providing a matrix for microbial proliferation while chlorpyrifos inhibit nitrification through toxicity effect on soil microorganisms. To validate these hypotheses, Experiments were carried out to estimate nitrification in rhizosphere of wheat under the influence of elevated CO2, chlorpyrifos and biochar. The experimental factors were CO2 (400 ppm, 800 ppm), biochar (0%, 1%), and chlorpyrifos (0 ppm, 10 ppm). The parameters were nitrification rate, abundance of 16S rRNA gene of eubacteria, abundance of amoA gene, plant shoot and root biomass. Nitrification rate and microbial parameters were lowest in the treatment of CO2 400 ppm biochar 0% chlorpyrifos 10 ppm and high under CO2 800ppm biochar 1% chlorpyrifos 0 ppm. Chlorpyrifos inhibited nitrification rates by 3 folds. Similarly, the abundances of 16S rRNA gene copies of eubacteria, ammonia oxidizing bacteria were inhibited 1.36 and 2.68 times by chlorpyrifos. Plant parameters (shoot and root biomass) were highest under elevated CO2 biochar 1% and chlorpyrifos 0 ppm and lowest in CO2 400 ppm biochar 0% and chlorpyrifos 10 ppm. Principal component analysis denoted that PC1 contributed 93.28% variation and PC2 contributed 4.40% variation. Study concludes that chlorpyrifos inhibit nitrification while elevated CO2 and biochar may alleviate these negative impacts aiding in retaining soil function.

Botanical insecticides effectively control chickpea weevil, Callosobruchus maculatus

Health hazards associated with the excess use of chemical insecticides used for the post-harvest preservation of food grains has prompted the emphasis on the use of natural insecticides in agriculture. In this regards, botanical insecticides have emerged as one of the best, safer, green, eco-friendly, promising and sustainable alternatives for controlling insect pests. Therefore, present study was aimed to evaluate the insecticidal and repellent activities of extracts of various plants such as Azadirachta indica (kernel), Allium sativum (bulb), Curcuma longa (rhizome), Citrus sinensis (peel), Citrus limon (peel), Murraya koenigii (leaves) and Eucalyptus sp. (leaves) against the chickpea weevil, Callosobruchus maculatus (Coleoptera: Chrysomelidae). These extracts exhibited potent insecticidal and repellent effects on C. maculatus. After 5 days treatment, all these extracts showed varying degree of insecticidal and repellent activity against C. maculatus; A. indica produced highest mortality (58%) followed by A. sativum (52.66% mortality) and C. longa (49.33% mortality) whereas C. sinensis exerted the lowest mortality (12.45%) against C. maculatus. All these extracts also showed good repellent activity, A. indica showed the highest index of repellency (IR) (0.53) followed by A. sativum (IR = 0.66), C. longa (IR = 0.73) and M. koenigii (IR = 0.86). These plant extracts also protected the chickpea grains from damage due to the beetle, A. indica provided 95.63% protection to chickpea grains against damage. Among the various extracts, extracts of A. indica (kernel), A. sativum (bulb) and C. longa (rhizome) proved to be promising insecticides and repellent against chickpea insect pest and can be used as effective, safer and green insecticides and repellents to preserve and protect chickpea grains against coleopteran pest.