Agricultural Insecticides Research Articles

Composition of soil organic matter drives total loss of dieldrin and dichlorodiphenyltrichloroethane in high-value pastures over thirty years.

The residues of dieldrin and dichlorodiphenyltrichloroethane (DDT), internationally-banned agricultural insecticides, continue to exceed government guidelines in some surface soils 30 years after use. Little is known regarding the soil factors and microbial community dynamics associated with the in-situ biodegradation of these organochlorine chemicals. We hypothesised that soil organic matter, a key factor affecting microbial biomass and diversity, affects the biodegradation and total loss of the pollutants 30 years after use. We sampled 12 contaminated paddocks with residue concentrations monitoring data since 1988 that represent two different agricultural surface-soils. The total loss and current concentrations of the residues was correlated with soil physicochemical properties, microbial biomass carbon, microbial community diversity indices and microbial community abundance. Current dieldrin and DDT residue concentrations were positively correlated with soil organic matter and clay contents. However, key indicators for loss of residues after 23-30 years were low carbon-to‑nitrogen ratios, high microbial-C-to-total-C ratios and high fungal community evenness. The results support the composition of soil organic matter as an important factor affecting degradation of organochlorines and that co-metabolism of dieldrin and DDT could be enhanced by manipulating the composition of soil organic matter to cater for a broad diversity of microbial function.

Quantifying Pesticide Exposure Risk for Monarch Caterpillars on Milkweeds Bordering Agricultural Land

Monarch butterflies are undergoing a long-term population decline, which has led to a search for potential causes underlying this pattern. One poorly studied factor is exposure to non-target pesticides on their primary host-plant, the common milkweed A. syriaca, during larval development. This species frequently grows near agricultural fields in the Midwestern U.S., but the spectrum of pesticides encountered by monarch caterpillars on milkweed leaves is unknown. Further, it is unclear whether pesticide exposure can be avoided by isolating restored milkweed patches at sites far from cropland. Over two years, we analyzed 1,543 milkweed leaves across seven sites in northwestern Indiana for the presence and concentration of a range of commonly used agricultural insecticides, fungicides, and herbicides. Additionally, we tested the ability of local (i.e., nearest linear distance to crop field) and landscape-level (i.e., % of corn/soybean in 1 km radius) variables to predict the presence of pesticides on focal milkweeds. Overall, we detected 14 pesticides—4 insecticides, 4 herbicides, 6 fungicides—on milkweeds that varied widely in their prevalence and concentration. The neonicotinoid clothianidin, the only pesticide for which toxicity data are available in monarchs, was detected in 15-25% of plants in June with nearly 60% of milkweeds at some sites testing positive (mean conc. = 0.71 and 0.48 ng/g in 2015 and 2016, respectively); however, no samples from July or August contained clothianidin. The related neonicotinoid thiamethoxam and the pyrethroid deltamethrin were detected in most (>75%) samples throughout the season, but only in the second year of the study. For thiamethoxam, isolating milkweeds 50-100 m from the nearest corn or soybean field tended to decrease the concentration and likelihood of detecting residues, whereas landscape composition surrounding milkweed sites had comparatively weak predictive power. These data suggest that monarch caterpillars frequently consume a diversity of pesticides in their diet; the lethal or sublethal impacts of this exposure remain to be tested.

Water temperature interacts with the insecticide imidacloprid to alter acute lethal and sublethal toxicity to mayfly larvae

ABSTRACTIncreased temperatures and exposure to agricultural insecticides are increasingly threatening freshwater ecosystems worldwide. However, their combined effects are still poorly understood. We investigated the individual and interactive effects of water temperature and imidacloprid, the most widely used neonicotinoid insecticide, on larvae of two New Zealand mayflies, Deleatidium spp. and Coloburiscus humeralis. Ninety-six-hour bioassays with imidacloprid were performed at 9, 12, 15, 18, 21 and 24°C, in a full-factorial design. Mayfly survivorship and sub-lethal responses of impairment and moulting were recorded. We documented synergistically increased mayfly mortality and immobility with exposure to imidacloprid at higher temperatures, implying temperature-enhanced toxicity of imidacloprid. Survivorship of both mayflies was synergistically reduced by the combination of imidacloprid exposure and increasing temperatures. The same interaction also affected mobility of C. humeralis and moulting frequency of Deleatidium. Our findings suggest that developing a more thorough understanding of temperature-contaminant interactions may be important to allow better protection of aquatic ecosystems.

Resistance of Culex pipiens pipiens (Diptera: Culicidae) to Pirmiphos-Methyl and Possible Link to Insecticide Usage in Agriculture and Public Health in Tunisia

Mosquito resistance to insecticides remains a growing concern in North Africa. The heavy reliance on insecticides and their recurrent and oftentimes inappropriate application are key sources for resistance, which is a potential threat to the global public health. Four populations of Culex pipiens pipiens were sampled from four areas of Tunisia, with the areas characterized by contrasting agricultural activity and usage of insecticides for vector control. Bioassays were performed to determine the level of resistance in each population to pirmiphos-methyl insecticide. Comparison of resistance ratios among the populations suggested a possible link of pirmiphos-methyl resistance with agricultural activity and insecticide usage. Little or no cross-resistance was observed with pirmiphos-methyl and either organophosphates or pyrethroids commonly used in those areas. Detoxification enzymes and target site (acetylcholinesterase) were involved in the observed resistance. Overall, the results of the present study suggest the role of insecticide usage and other activities in the immediate area in impacting the development of insecticide resistance in mosquitoes, with a possible major factor being agricultural activities.

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.

Toxicolgical impact of chlorpyrifos and ameliorative potentials of vitamin e on nuclear abnormalities in erythrocytes of <i>Heteroclarias</i>

Chlorpyrifos is commonly used as an agricultural insecticide which is extremely toxic to non-target organisms like fish. The effect of chlorpyrifos and ameliorative potentials of vitamin E on nuclear abnormalities in the erythrocytes of Heteroclarias was investigated. Juveniles Heteroclarias were exposed to varying concentrations (0, 1, 2, 3, 4 and 5 ppm) of chlorpyrifos for 96 hours and fed on varying concentrations (50, 250, 500 and 1000 mg/kg diet) of vitamin E for 28 days. The LC50 value was calculated as 2.4 ppm. After the exposure period, the fish were sacrificed and blood was collected for micronucleus assay. Different abnormalities such as micronucleated, binucleated, multinucleated and altered cells were evident in the erythrocytes of chlorpyrifos-exposed fish compared to control. The micronucleus induction and percentage frequency increased (P<0.05) as the concentration of chlorpyrifos increased, but, decreased (P<0.05) in the groups ameliorated with vitamin E. However, a gradual decrease occurred as the concentration of vitamin E inclusion in the diet increased with a great reduction (P<0.05) in the group fed on 500 mg vitamin E/kg diet. This study revealed that chlorpyrifos induced micronucleus formation, but, 500mg vitamin E/kg diet is capable of minimizing micronucleus formation in Heteroclarias.Keywords: Amelioration, Chlorpyrifos, Heteroclarias, Micronucleus, vitamin E

The Molecular Recognition Of The Insecticide Sulfoxaflor By Nicotinic Receptors Is Based On Atomic Interactions Identical To Bee‐Harming Neonicotinoids

Neonicotinoids, sometimes called ‘neonics’, are a class of insecticides targeting neuronal nicotinic acetylcholine receptors, which belong to the family of pentameric ligand-gated ion channels (pLGICs) or Cys-loop receptors. The widespread application of these neurotoxic insecticides in agriculture is tied to the worldwide decline of bee populations, due to their sublethal effects on bee memory, behavior and reproduction. In 2018, the member states of the European Union, agreed on a ban of most neonicotinoids, with exemption for greenhouses. However, a new generation of sulfoximine-based insecticides, such as sulfoxaflor, has recently been introduced to the agricultural market claiming they are chemically distinct from neonicotinoids. Using the acetylcholine binding protein (AChBP) as a well-established tool for structural studies of nicotinic receptors, we engineered AChBP variants that reliably mimic the neurotransmitter binding site of honeybee nicotinic receptors. Three-dimensional structures of sulfoxaflor-bound receptors reveal, despite the distinct chemistry claim, that the molecule is recognized through receptor interactions that are virtually identical to neonicotinoids. This observation suggests that sulfoximine- and neonicotinoid-type insecticides share a common mode of action, and that the legislative ban on certain insecticides should, as a precaution, be expanded based on pharmacological activity at their target receptors rather than on chemical composition. Crystal structure of an insect nicotinic receptor mimic (iAChBP) in complex with the insecticide sulfoxaflor. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Many faces of arsenic

Abstract Arsenic (As) is a natural component of the Earth’s crust. Due to its specific properties, arsenic became e.g. the favorite poison in the 19th century in Europe, a component of an effective insecticide and herbicide in agriculture, a specific chemical weapon during World War II and a medication used to treat various diseases. The bad reputation of this element was confirmed after World War II, when arsenic-based chemical weapons were dumped on the seabed and became a potential threat to the marine ecosystem. The wide distribution of arsenic compounds in the environment necessitated the development of technologies aimed at removing arsenic from the aquatic ecosystem. This study provides a detailed overview of the occurrence, distribution and transformation of arsenic species in the aquatic environment.

Molecular interactions of chlorpyrifos and its environmental degradation products with human sex hormone-binding globulin: an in silico study.

In recent years, there has been a widespread interest and awareness about health issues posed by endocrine-disrupting chemicals present in the environment. These chemicals, often present in food and many consumer products, can interfere with hormone biosynthesis and metabolism and may result in deviation from normal homeostatic control. Chlorpyrifos (CPF), a major endocrine-disrupting chemical is used worldwide as an agricultural insecticide against a broad spectrum of insect pests in rice cultivation and to control termites. The insecticide mostly undergoes environmental degradation to chlorpyrifos-oxon (CPYO), des-ethyl chlorpyrifos (DEC), 3,5,6-trichloro-2-methoxypyridine (TMP) and 3,5,6-trichloro-2-pyridinol (TCP). Results from several epidemiological studies suggest that exposure to CPF can result in reproductive disorders, including infertility in male and female. Sex hormone-binding globulin (SHBG) is a circulatory protein that binds sex steroids and is a potential target for endocrine disruptors in the human body. The objective of the present study involved computational approaches to apprehend the mechanism of molecular interaction of CPF and its four degradation products (CPYO, DEC, TMP, TCP) with human SHBG using molecular docking simulation. All five compounds (CPF, CPYO, DEC, TMP, TCP) showed high binding affinity with SHBG; however, the binding affinity values were higher (more negative) for CPF, CPYO, DEC and TMP than for TCP indicating that CPF, CPYO, DEC and TMP formed a tight interaction with SHBG. From the results obtained with the docking analysis, it can be opined that CPF, CPYO, DEC and TMP could possibly act as potential endocrine disruptors for androgen signaling.

The protective effects of the antioxidant N-acetylcysteine (NAC) against oxidative stress-associated apoptosis evoked by the organophosphorus insecticide malathion in normal human astrocytes

Malathion is one of the most widely used organophosphorus insecticides in agriculture. However, malathion may be involved in the etiology of human brain dysfunction. Induction of ROS has been proposed as a mechanism of malathion-induced poisoning cases, but there are few data regarding the effects of malathion on oxidative stress-associated neurotoxicity in human glial cells. The aim was to explore the mechanism underlying effects of malathion on neurotoxicity in Gibco® Human Astrocytes (GHA cells) and evaluate the protective effects of the antioxidant (N-acetylcysteine, NAC). Cell viability was measured by the cell proliferation reagent (WST-1). Antioxidant enzymes (glutathione peroxidase and catalase) were measured by an ELISA reader. Cell cycle distribution and ROS productions were detected by flow cytometry. Cell cycle-related protein levels (cyclin E1, CDK2, cyclin A2, CDK1/CDC2, or cyclin B1) and apoptotic protein levels (Bcl-2, Bax, and cleaved caspase-9/caspase-3) were analyzed by Western blotting. In GHA cells, treatment with malathion (10–25 μM) for 24 h concentration-dependently induced cytotoxicity and cell cycle arrest. In terms of oxidative stresses, malathion elevated intracellular ROS levels, but reduced glutathion and antioxidant enzyme levels. Treatment with NAC (5 μM) reversed malathion-induced oxidative stress responses, and prevented malathion-evoked apoptosis by regulating apoptotic protein expressions. Together, in GHA cells, NAC mediated inhibition of malathion-activated mitochondrial apoptotic pathways that involved cell cycle arrest and ROS responses. These data provide further insights into the molecular mechanisms behind malathion poisoning, and might suggest that NAC with its protective effects may be a potential compound for prevention of malathion-induced brain injury.

Impact of chronic low dose exposure of monocrotophos in rat brain: Oxidative/ nitrosative stress, neuronal changes and cholinesterase activity.

Monocrotophos (MCP) is an organophosphate mainly used as insecticides in agriculture, and veterinary practice to control pests. Exposure to MCP is known to induce significant systemic toxicity in animals and humans. Short term exposure to a high dose of MCP has been reported to cause systemic toxicity, however limited information is available regarding low dose long term exposure in rats. We studied the effects of low dose long term exposure to MCP on oxidative/nitrosative stress, cholinesterase activity and neuronal loss in rat. Male rats were exposed to MCP (0.1 μg or 1 μg/ml) via drinking water for 8 weeks. The pro-oxidant markers such as reactive oxygen species (ROS), lipid peroxidation (MDA), nitrite level and antioxidant markers such as reduced glutathione (GSH), superoxide dismutase (SOD), catalase (CAT) and inhibition of cholinesterase activities were measured to evaluate the effects of MCP on brain along with plasma cholinesterase activity. Neuronal loss was analyzed in cortical region using H&E stained slices. The results suggested that exposure to MC even at the low dose, increased reactive oxygen species, thiobarbituric acid reactive substance levels and decreased glutathione, superoxide dismutase, catalase and cholinesterase activities in brain. No significant effect however, was observed on nitrite levels. Histological analysis revealed that low dose MCP exposure lead to structural changes in the cortical neurons in rats. It can be concluded from the study that low dose long term exposure (lower than No Observed Effect Level) of MCP may lead to the generation of oxidative stress by elevation of pro-oxidants markers and depletion of antioxidant enzymes markers along with inhibition of cholinesterase activity. These changes might thus be considered as the possible mechanism of cortical neuronal loss in these animals.

Fipronil pesticide as a suspect in historical mass mortalities of honey bees

Mass mortalities of honey bees occurred in France in the 1990s coincident with the introduction of two agricultural insecticides, imidacloprid and fipronil. Imidacloprid, a neonicotinoid, was widely blamed, but the differential potency of imidacloprid and fipronil has been unclear because of uncertainty over their capacity to bioaccumulate during sustained exposure to trace dietary residues and, thereby, cause time-reinforced toxicity (TRT). We experimentally quantified the toxicity of fipronil and imidacloprid to honey bees and incorporated the observed mortality rates into a demographic simulation of a honey bee colony in an environmentally realistic scenario. Additionally, we evaluated two bioassays from new international guidance for agrochemical regulation, which aim to detect TRT. Finally, we used analytical chemistry (GC-MS) to test for bioaccumulation of fipronil. We found in demographic simulations that only fipronil produced mass mortality in honey bees. In the bioassays, only fipronil caused TRT. GC-MS analysis revealed that virtually all of the fipronil ingested by a honey bee in a single meal was present 6 d later, which suggests that bioaccumulation is the basis of TRT in sustained dietary exposures. We therefore postulate that fipronil, not imidacloprid, caused the mass mortalities of honey bees in France during the 1990s because it is lethal to honey bees in even trace doses due to its capacity to bioaccumulate and generate TRT. Our results provide evidence that recently proposed laboratory bioassays can discriminate harmful bioaccumulative substances and, thereby, address evident shortcomings in a regulatory system that had formerly approved fipronil for agricultural use.

Genotoxic and oxidative damage in the freshwater teleost Prochilodus lineatus exposed to the insecticides lambda-cyhalothrin and imidacloprid alone and in combination

In agricultural areas insecticides mixtures are frequently used, such as the combination of the pyrethroid lambda-cyhalothrin (LC) together with the neonicotinoid imidacloprid (IMI). Because of their extensive use, these insecticides can be found in freshwater bodies producing effects on aquatic organisms. However, there is a lack of studies concerning the combined effects of LC and IMI and their possible interactions. The objective of this study was to evaluate genotoxic and oxidative effects of LC and IMI, isolated and in binary mixture, on the neotropical freshwater teleost curimba (Prochilodus lineatus). Juveniles of P. lineatus were exposed to LC (0.15 μg L−1), IMI (100 μg L−1), LC + IMI or only to water (CTR) for 48, 96, 144 and 192 h. The occurrence of DNA damage (comet assay), was evaluated in erythrocytes, gills, liver and brain cells, the frequency of micronucleus (MN) and nuclear abnormalities (ENA) was measured in erythrocytes and protein carbonylation (PCC) and lipid peroxidation (LPO) were determined in gills, liver and brain. The results showed that LC and IMI, both alone and in combination, cause DNA damage in different tissues and ENA in the erythrocytes of P. lineatus. In addition, after shorter exposures a synergistic interaction between the insecticides was found in the blood and in the liver. LC showed to be the most toxic insecticide, even at much lower concentrations than IMI, causing DNA damage in all tissues analyzed, indicating that the effect of mixture is mainly due to the presence of the pyrethroid. The mixture LC + IMI also caused an increase in PCC and LPO in gills and liver after shorter exposures, indicating a probable synergistic interaction. The result of this interaction leads to an increased toxicity in shorter times, which can be harmful to fish in their natural environment.

Meta-Analysis of Insecticides in United States Surface Waters: Status and Future Implications.

Agricultural insecticides occur in U.S. surface waters, yet our knowledge of their current and potential future large-scale risks for biodiversity is restricted. Here, we conducted a meta-analysis of measured insecticide concentrations (MICs; n = 5817; 1962-2017) in U.S. surface waters and sediments reported in 259 peer-reviewed scientific studies for 32 important insecticide compounds and their degradation products ( n = 6). To assess overall and substance-specific ecological risks and future implications, MICs were compared with official U.S. Environmental Protection Agency regulatory threshold levels (RTLs) and insecticide use trends. Approximately half of the MICs, i.e., 49.4% (at 69.7% of the 644 sites covered), exceeded their RTLs, indicating substantial risks to the integrity of U.S. aquatic ecosystems and potential shortcomings of regulatory risk assessment procedures. Overall, pyrethroids had the highest exceedance rate (80.7%; n = 1808), followed by organophosphates and carbamates (42.2%, n = 2618), and organochlorines (33.3%, n = 468). Pronounced increasing use trends were found for neonicotinoids, which exceeded their chronic RTLs, i.e., those of high relevance due to neonicotinoids̀ persistence in surface waters, for 56.8% of MICs (22.2% for acute RTLs). A regression analysis of insecticide use trends, although to be interpreted with care, indicated a future increase in applied amounts of several high risk insecticides such as pyrethroids and neonicotinoids, suggesting elevated prospective risks for U.S. surface waters, biodiversity, and endangered species.

Interaction of Bombyx mori aminopeptidase N and cadherin-like protein with Bacillus thuringiensis Cry1Ac toxin

Bacillus thuringiensis (Bt) produces Cry toxins that are widely used as insecticides in agriculture and forestry. Receptors are important to elucidate the mode of interaction with Cry toxins and toxicity in lepidopteran insects. Here, we purified the Cry toxin from Bt and identified this toxin by flight mass spectrometry as Cry1Ac, and then recombinantly expressed aminopeptidase N (BmAPN6) and repeat domains of cadherin-like protein (CaLP) of B. mori. Using co-immunoprecipitation (co-IP), Far-Western blotting, and enzyme-linked immunosorbent assays (ELISAs), we identified the interaction between Cry1Ac and BmAPN6. Furthermore, analysis of the cytotoxic activity of Cry1Ac toxin in Sf9 cells showed that BmAPN6 directly interacted with Cry1Ac toxin to induce morphological aberrations and cell lysis. We also used co-IP, Far-Western blotting and ELISAs to analyze the interactions of Cry1Ac with three binding sites corresponding to cadherin repeat (CR) 7 CR11, and CR12 of CaLP. Notably, the three repeat domains were essential Cry1Ac binding components in CaLP. These results indicated that BmAPN6 and CaLP served as a functional receptor involved in Bt Cry1Ac toxin pathogenicity. These findings represent an important advancement in our understanding of the mechanisms of Cry1Ac toxicity and provide promising candidate targets for gene editing to enhance resistance to pathogens and increase the economic value of B. mori.

Insecticidal properties of pyripyropene A, a microbial secondary metabolite, against agricultural pests.

We previously reported the strong insecticidal activity of a microbial secondary metabolite, pyripyropene A (PP-A), against aphids. Pyripyropenes (PPs) have been known to show weak feeding inhibition against lepidopteran pests, but their strong aphicidal activities were first reported in our former study. Here we investigated the details of the insecticidal property of PP-A. Our biological evaluation of PP-A found that it shows high insecticidal activities against some sucking pests, such as whiteflies, as well as aphids, and preferable biological profiles as agricultural insecticides. Furthermore, PP-A controlled aphids well under field conditions.

Combining QTL mapping with transcriptome and metabolome profiling reveals a possible role for ABA signaling in resistance against the cabbage whitefly in cabbage.

Whiteflies are among the world’s most significant agricultural pests and chemical insecticides are extensively used to reduce crop damage to acceptable levels. However, nearly all insecticides pose a threat to the environment and alternative control methods, such as breeding of crop varieties that are inherently insect-resistant, are needed. Previously, a strong source of plant-age dependent resistance to the cabbage whitefly (Aleyrodes proletella) has been identified in the modern white cabbage (Brassica oleracea var. capitata) variety Rivera. However, nothing is known about the molecular mechanisms or the genes involved in this resistance. In the present study, a multidisciplinary approach combining transcriptome and metabolome profiling with genetic mapping was used to identify the molecular players of whitefly resistance in cabbage. Transcriptome profiles of young (susceptible) and older (resistant) Rivera plants were analyzed using RNA sequencing. While many genes involved in general processes were differentially expressed between both ages, several defense-related processes were overrepresented in the transcriptome profile of older plants. Hormone measurements revealed that jasmonic acid (JA) levels decreased upon whitefly infestation at both plant ages. Interestingly, abscisic acid (ABA) levels showed contrasting effects in response to whitefly infestation: ABA levels were reduced in young plants but induced in older plants upon whitefly feeding. Auxin levels were significantly lower in older plants compared with young plants, independent of whitefly presence, while glucosinolate levels were higher. Additionally, whitefly performance was monitored in an F2 population derived from a cross between Rivera and the susceptible white cabbage variety Christmas Drumhead. Significant QTL intervals were mapped on chromosome 2 and 9 for oviposition rate and whitefly adult survival, respectively. Several genes that were higher expressed in older plants and located in the identified QTL intervals were orthologous to Arabidopsis genes that have been related to ABA signaling, suggesting a role for ABA in the regulation of resistance towards whiteflies. Our results show that combining different omics approaches is a useful strategy to identify candidate genes underlying insect resistance.

Adverse effects of a synthetic pyrethroid insecticide cypermethrin on life parameters and antioxidant responses in the marine copepods Paracyclopina nana and Tigriopus japonicus

To find the adverse effects induced by cypermethrin, the ecotoxicological model copepods Tigriopus japonicus and Paracyclopina nana were exposed under cypermethrin, which is a widely used type-II pyrethroid insecticide in agriculture. Despite its large-scale application as insecticide in agriculture, little information is available on its adverse effects on aquatic invertebrates. In this study, the toxicity of cypermethrin on two copepods was assessed based on life parameters (growth rate and reproduction), oxidative stress and consequent antioxidant enzymatic activities, and gene expression profiles of antioxidants. The acute toxicity alone demonstrated that P. nana is less tolerant and sensitive against cypermethrin, compared to T. japonicus. However, under chronic exposure, life parameters of both P. nana and T. japonicus were severely affected by cypermethrin. Among antioxidant enzymatic activities, superoxide dismutase (SOD) and glutathione S-transferase (GST), in particular, demonstrated significant increase in response to cypermethrin. Furthermore, temporal-mRNA expression profile showed modulations in antioxidant related genes in response to cypermethrin. Our results provide the underlying toxic mechanism of cypermethrin and the oxidative stress defense mechanism and species-specific tolerance against cypermethrin in two model copepods species.

A new concept for controlling tiny-scale insect pest in green house – noval technology to apply liquid ethyl formate:

As increased agricultural insecticide uses and trends in insecticide resistance, increased labor cost to apply insecticide and limited its application to fertility season in green house. There is a need of a safe, labor-saving and confined space application concept to manage control tiny-scale insect pest such as thrips and whitefly. Fumigation with ethyl formate (EF), which is considered as effective to various insect pest and safely use in quarantine treatment, was evaluated in the confined space (glass house) and semi-confined space (vinyl house). The new application technology for application of liquid EF could be the one of the key options for control of tiny flying insects in greenhouses that would save labor and operation costs. It could be connected to smartfarm technologies in the near future.

Carbamate resistance in a UK population of the halophilic mosquito Ochlerotatus detritus implicates selection by agricultural usage of insecticide

The salt marsh mosquito Ochlerotatus detritus Haliday, 1833 (Diptera: Culicidae) is locally abundant in some areas of the UK, can be a pernicious summer nuisance biter and is one of eleven British mosquitoes considered as a potential bridge vector of West Nile Virus. WHO bioassays of insecticide susceptibility were performed on O. detritus from Parkgate Marshes, Little Neston, Wirral, UK using three insecticides, the pyrethroid permethrin, the carbamate bendiocarb and the organophosphate fenitrothion. O. detritus were fully susceptible to permethrin and fenitrothion but exhibited strong resistance to bendiocarb (66% of females alive following 1–hr exposure; LT50 of 116 minutes). Sequencing of the known resistance-causing mutations in the acetylcholinesterase target site of carbamate/organophosphates, and of pyrethroids, the voltage-gated sodium channel, revealed no known target-site mutations indicating the carbamate resistance is not target-site mediated. Pre-exposure to the synergist piperonyl butoxide recovered full bendiocarb susceptibility further implicating metabolic resistance. We show that UK mosquitoes have the potential to develop resistance to insecticides and suggest that the carbamate resistance detected could be a result of exposure to agricultural insecticides.