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Applied aspects of neonicotinoid uses in crop protection
Abstract
Neonicotinoid insecticides comprise seven commercially marketed active ingredients: imidacloprid, acetamiprid, nitenpyram, thiamethoxam, thiacloprid, clothianidin and dinotefuran. The technical profiles and main differences between neonicotinoid insecticides, including their spectrum of efficacy, are described: use for vector control, systemic properties and versatile application forms, especially seed treatment. New formulations have been developed to optimize the bioavailability of neonicotinoids through improved rain fastness, better retention and spreading of the spray deposit on the leaf surface, combined with higher leaf penetration. Combined formulations with pyrethroids and other insecticides are also being developed with the aim of broadening the insecticidal spectrum of neonicotinoids and to replace WHO Class I products from older chemical classes. These innovative developments for life-cycle management, jointly with the introduction of generic products, will, within the next few years, turn neonicotinoids into the most important chemical class in crop protection.
... Neonicotinoids are often referred to as 'systemic', which means that they are absorbed by treated plants and spread to all tissues through the vascular system (Elbert et al., 2008). This makes the plant toxic for insects ingesting parts of it or sucking its circulating fluids. ...
... The neonicotinoids in agricultural use and their structures are shown in Figure A4.1 as well as the manufacturers of each variant (Elbert et al., 2008). ...
... Neonicotinoids can be applied as seed coatings, soil drenches, foliar sprays, by injection into trees and shrubs, Figure A4.1 Chemical structure of neonicotinoid insecticides and year of market introduction (Elbert et al., 2008). or by addition to irrigation water. ...
... It is therefore necessary to develop a better management strategy to control wheat aphids. Seed treatments in cotton, corn, cereal, sugar beet, and oilseed rape with neonicotinoid compounds such as imidacloprid, thiamethoxam, dinotefuran, and thiacloprid are effective for the control of sucking insect pests such as aphids, whiteflies, plant hoppers, and thrips; chewing pests, including some lepidopteran pests; and a number of coleopteran pests [18][19][20][21][22][23][24]. Among those seed treatment ingredients, imidacloprid has the longest history (since 1991) of improving crop protection against sucking insect pests because of its broad insecticidal spectrum, systemic action, and low residue [18,20,25]. ...
... Seed treatments in cotton, corn, cereal, sugar beet, and oilseed rape with neonicotinoid compounds such as imidacloprid, thiamethoxam, dinotefuran, and thiacloprid are effective for the control of sucking insect pests such as aphids, whiteflies, plant hoppers, and thrips; chewing pests, including some lepidopteran pests; and a number of coleopteran pests [18][19][20][21][22][23][24]. Among those seed treatment ingredients, imidacloprid has the longest history (since 1991) of improving crop protection against sucking insect pests because of its broad insecticidal spectrum, systemic action, and low residue [18,20,25]. Imidacloprid seed treatment was observed to reduce pest density on maize, such as that of wireworms, cutworms, aphids, leafhoppers, and frit fly (Oscinella frit L.) [26,27]. ...
... Imidacloprid seed treatment can protect young plants from attack by insect pests and is also better for environmental safety than seed treatments with other pesticides [10,20]. Because of these factors, imidacloprid seed treatments are widely used in cotton, corn, cereals, sugar beet, oilseed rape, and other crops [20]. ...
Imidacloprid seed treatments are effective at reducing the cohorts of many insect pests on crops such as cotton, corn, and cereals. The effects of imidacloprid seed treatments depend on the aphid species. In China, there are four wheat aphid species—Sitobion avenae (Fabricius), Rhopalosiphum padi (Linnaeus), Schizaphis graminum (Rondani), and Metopolophium dirhodum (Walker)—and for a given region, these four aphid species differ in dominance with changes in cultivation practices and climate. Therefore, it is necessary to evaluate the effects of imidacloprid seed treatments on the four different aphid species. In experiments in the laboratory, imidacloprid seed treatments significantly reduced the survival rates of S. avenae, R. padi, and S. graminum to 57.33 ± 2.86%, 12.67 ± 1.92%, and 20.66 ± 2.33%, respectively, but for M. dirhodum, there was no significant difference between the control (96.33 ± 1.08%) and the treatment (97.00 ± 0.98%). The fecundities of the four aphid species were much reduced, especially for R. padi when feeding on treated wheat plants. For the field survey, only three aphid species were considered because the density of S. graminum was too low to be analyzed. The effects of imidacloprid seed treatment on the three aphid species in the field were consistent with the laboratory results. Imidacloprid seed treatment reduced the population sizes of S. avenae and R. padi at rates of 70.30 ± 3.15% and 87.62 ± 2.28%, respectively, for the whole wheat season in the field. For M. dirhodum, imidacloprid seed treatments were less effective, and the densities of M. dirhodum increased on four sample days. From this study, we confirmed that the effect of imidacloprid seed treatment varied with the composition of aphid species, being especially less effective for M. dirhodum.
... In the neonicotinoids group, the insecticide imidacloprid stands out as a nicotinic acetylcholine receptors (nAChR) blocker and GABA receptor antagonist, causing changes in the nervous system of insects (Elbert et al., 2008;Lhara and Matsuda, 2018;Lu et al., 2023;Matsuda et al., 2020). Given the risks they pose to pollinating insects, their use has been limited. ...
... Imidacloprid is a systemic insecticide that can translocate through plant tissues of the vascular system (Bonmatin et al., 2015;Elbert et al., 2008). Thus, it can reach colonies through the transport of contaminated pollen and nectar and, consequently, through social contact (insect-insect) (Bommuraj et al., 2021;Carneiro et al., 2022;Tsvetkov et al., 2017). ...
Apis mellifera L. (Hymenoptera: Apidae) is fundamental in the production chain, ensuring food diversity through the ecosystem service of pollination. The aim of this work was to evaluate the impact of imidacloprid, orally, topically, and by contact, on A. mellifera workers and to verify the presence of this active ingredient in honey. Toxicity levels were verified by bioassays. In bioassay 1, the levels correspond to the percentages of 100, 10, 1, 0.1, and 0.01% of the recommended concentration for field application of the commercial product Nortox® (active ingredient imidacloprid), with which we obtained the mean lethal concentration (LC50) in 48 h for A. mellifera, determining the concentration ranges to be used in the subsequent bioassays. Bioassays 2 and 3 followed the guidelines of the Organization for Economic Cooperation and Development, which specify the LC50 (48 h). In bioassay 4, the LC50 (48 h) and the survival rate of bees for a period of 120 h were determined by contact with a surface contaminated with imidacloprid, and in bioassay 5, the interference of the insecticide with the flight behavior of bees was evaluated. Honey samples were collected in agroecological and conventional georeferenced apiaries and traces of the imidacloprid were detected by means of high-performance liquid chromatography (HPLC-UV) with extraction by SPE C18. Bee survival was directly affected by the concentration and exposure time, as well behavioral performance, demonstrating the residual effect of imidacloprid on A. mellifera workers. Honey samples from a conventional apiary showed detection above the maximum residue limits (MRL) allowed by the European Union (0.05 μg mL-1), but samples from other apiaries showed no traces of this insecticide. Imidacloprid affects the survival rate and behavior of Africanized A. mellifera and honey quality.
... All these insecticides of neonicotinoid group are neurotoxin and effect on acetylcholine receptors. (Elbert et al., 2008;Matsuda et al., 2001). Among these insecticides imidacloprid which introduced in the market in early 1990s and acetamiprid are extensively used by spraying and as a seed dressing on agriculture crops throughout the world to control insect pests (Elbert et al., 2008). ...
... (Elbert et al., 2008;Matsuda et al., 2001). Among these insecticides imidacloprid which introduced in the market in early 1990s and acetamiprid are extensively used by spraying and as a seed dressing on agriculture crops throughout the world to control insect pests (Elbert et al., 2008). All the insecticides are tested under laboratory and field conditions than approved for commercial use, this risk assessment process confirm that they are harmful or harmless for non-target organisms including these important pollinators. ...
midacloprid and acetamiprid are neonicotinoid insecticides introduced in the market for the control of insect pests of agricultural crops, but unfortunately these insecticides are causing harmful effect on non-target organisms including honeybees and bumblebees. Insecticides of this group effect acetylcholine nicotinic receptors. Apis mellifera, the European honeybee and Bombus haemorrhoidalis are important pollinators for wild and managed crops in Pakistan, but unfortunately their population is declining day by day at alarming rate. This study was design to find out the susceptibility level and insecticidal toxicity comparison on A. mellifera and B. haemorrhoidalis to acetamiprid and imidacloprid under controlled laboratory conditions by using contact and oral exposure methods. The results of oral method by using sugar solution showed that honeybee is more susceptible as compared to bumblebee on both insecticides. Maximum mortality i.e. 20%, 35%, 66%, in honeybee and 16%, 29%, 45% in bumblebee workers at acetamiprid and at imidacloprid 46%, 67%, 83% in honeybee and 34%, 56%, 72% in bumblebee were observed respectively after the exposure of 3hrs. 6hrs. and 24hrs. Similar susceptibly results were found on pollen and contact method. Overall results demonstrate that these both neonicotinoid insecticides are toxic for bumblebees and honeybees, and honeybee workers are more susceptible as compared to bumblebee workers at company recommended field realistic dose.
... The use of pesticides in seed treatment is a preventive approach to insect pest management. Once in the seed, the high solubility allows the active ingredient to move through the plant fluids, protecting the seedlings against sucking pest insects (Elbert et al., 2008;Simon-Delso et al., 2015). Treated seeds with pesticides can represent a risk to seedeating wildlife if are available in the field. ...
The wide use of neonicotinoid seed treatment represents a hazard for farmland birds that feed on treated seeds. This study aimed to characterize the long-term effects of the neonicotinoid imidacloprid (IMI) in the passerine grayish baywing (Agelaioides badius). The birds were fed ad libitum for 32 days only with seeds treated with 53.1 (Low, 11 % of LD50) and 514 (High, (112 % of LD50) mg IMI/kg seed; these concentrations representing respectively, 1.8 and 17.1 % of 3 g IMI/kg, an average application rate used to treat crop seeds in Argentina. The effects exerted by IMI on birds were evaluated at behavioral, physiological, hematological, genotoxic, and biochemical levels. No differences in food consumption were observed between Control and Low treatments birds, indicating a lack of aversion to treated seeds. High treatment birds only decreased their food consumption by 20 % in the first 3 days of exposure. Birds from High treatment experienced an early loss of body weight, reduction in their mobility, lack of response to threats (i.e., predator call and approaching person), and altered their use of the cage. On the contrary, birds from Low treatment experienced a delay in the onset of effects like reduction in mobility, lack of response to threats, and a tendency to reduce their body weight. At the end of exposure, glutathione S transferase activity in the plasma of treated birds decreased, and cholinesterase activity increased in the liver of treated birds. This study highlights that consumption equivalent to 1.8 % of the daily diet of baywings as IMI-treated seeds, is sufficient to generate behavioral and physiological alterations and death. In the wild, these effects may have ecological consequences, by impairing the survival of birds, representing a risk to farmland bird populations.
... Honeydew, the sugary excretion of aphids and other Hemiptera, is also commonly used by parasitic wasps as a carbohydrate source and may contain biologically active levels of insecticides (Calvo-Agudo et al., 2019. Because all nAChR agonists tested in the present study are widely used against hemipteran pests such as aphids, whiteflies, and thrips (Elbert et al., 2008;Nauen et al., 2015;Zhu et al., 2011), it can be expected that these substances may enter beneficial insects also via honeydew, although data on residue levels are not yet available. The question of whether parasitic wasps, because of their particular lifestyle, can also take up bioactive doses of pesticides when developing in or host-feeding on contaminated hosts and whether the ingested amounts are sufficient to affect olfactory responses is still largely unresolved and requires further research. ...
Lethal and sublethal effects of pesticides on non-target organisms are one of the causes of the current decline of many insect species. However, research in the past decades has focused primarily on pollinators, although other beneficial non-target organisms such as parasitic wasps may also be affected. We studied the sublethal effects of the four insecticides acetamiprid, dimethoate, flupyradifurone, and sulfoxaflor on pheromone-mediated sexual communication and olfactory host finding of the parasitic wasp Nasonia vitripennis. All agents target cholinergic neurons, which are involved in the processing of chemical information by insects. We applied insecticide doses topically and tested the response of treated wasps to sex pheromones and host-associated chemical cues. Additionally, we investigated the mating rate of insecticide-treated wasps. The pheromone response of females surviving insecticide treatment was disrupted by acetamiprid (≥0.63 ng), dimethoate (≥0.105 ng) and flupyradifurone (≥21ng), while sulfoxaflor had no significant effects at the tested doses. Olfactory host finding was affected by all insecticides (acetamiprid: ≥1.05 ng, dimethoate: ≥0.105 ng, flupyradifurone: ≥5.25 ng, sulfoxaflor: ≥0.52 ng). Remarkably, females treated with ≥0.21 ng dimethoate even avoided host odor. The mating rate of treated N. vitripennis couples was decreased by acetamiprid (6.3 ng), flupyradifurone (≥2.63 ng) and sulfoxaflor (2.63 ng) while dimethoate showed only minor effects. Finally, we determined the amount of artificial nectar consumed by N. vitripennis females within 48 hours. Considering this amount (approximately 2 µl) and the maximum concentrations of the insecticides reported in nectar, tested doses can be considered field realistic. Our results suggest that exposure of parasitic wasps to field-realistic doses of insecticides targeting the cholinergic system reduces their effectiveness as natural enemies by impairing the olfactory sense.
... Bees' exposure to neonicotinoids occurs mainly through the ingestion of residues in pollen and nectar of contaminated plants (Desneux et al., 2007;Sánchez-Bayo et al., 2016). When neonicotinoid is ingested by the bee, it acts on the insect nicotinic acetylcholine receptor (Elbert et al., 2008) and has the ability to disrupt neuronal cholinergic signaling (Fischer et al., 2014). One of the most important problems of pesticide use is the off-target effects on beneficial insects such as bees exposed during pollination activities (Botías et al., 2015). ...
Neonicotinoids are the most widely used pesticide compared to other major insecticide classes known worldwide and have the fastest growing market share. Many studies showed that neonicotinoid pesticides harm honeybee learning and farming activities, negatively affect colony adaptation and reduce pollination abilities. Bumblebees are heavily preferred species all over the world in order to ensure pollination in plant production. In this study, sublethal effects of the neonicotinoid insecticide thiamethoxam on the brain of Bombus terrestris workers were analyzed. Suspensions (1/1000, 1/100, 1/10) of the maximum recommended dose of thiamethoxam were applied to the workers. 48 h after spraying, morphological effects on the brains of workers were studied. According to area measurements of ICC's of Kenyon cells, there was a significant difference between 1/10 dose and all groups. On the other hand, areas of INC's of Kenyon cells showed a significant difference between the control group and all dose groups. Neuropil disorganization in the calyces increased gradually and differed significantly between the groups and was mostly detected at the highest dose (1/10). Apart from optic lobes, pycnotic nuclei were also observed in the middle region of calyces of mushroom bodies in the high dose group. Also, the width of the lamina, medulla and lobula parts of the optic lobes of each group and the areas of the antennal lobes were measured and significant differences were determined between the groups. The results of the study revealed that sublethal doses of thiamethoxam caused some negative impacts on brain morphology of B. terrestris workers.
... Chemical insecticides (i.e. from artificially derived substances) such as organochlorines, carbamates, pyrethroids and organophosphates were in use already before the launch of the neonicotinoid insecticides in the 1990s. The availability of neonicotinoids resulted in a shift and dramatic increase in the use of this particular insecticide class, which soon had the highest market share of any insecticide class in the world in 2008 at 24% (Elbert et al., 2008;Jeschke et al., 2011) which was followed by pre-existing pyrethroids (16%), organophosphates (14%) and carbamates (11%). However, the use of the neonicotinoids has been restricted in various regions such as the EU, where three neonicotinoids are banned from outdoor use since 2018 (EC, 2013;EC, 2018a;EC, 2018b;EC, 2018c). ...
Synthetic pesticides (e.g. herbicides, fungicides and insecticides) are used widely in agriculture to protect crops from pests, weeds and disease. However, their use also comes with a range of environmental concerns. One key concern is the effect of insecticides on non-target organisms such as bees, who provide pollination services for crops and wild plants. This systematic literature review quantifies the existing research on bees and insecticides broadly, and then focuses more specifically on non-neonicotinoid insecticides and non-honeybees. We find that articles on honeybees (Apis sp.) and insecticides account for 80% of all research, with all other bees combined making up 20%. Neonicotinoids were studied in 34% of articles across all bees and were the most widely studied insecticide class for non-honeybees overall, with almost three times as many studies than the second most studied class. Of non-neonicotinoid insecticide classes and non-honeybees, the most studied were pyrethroids and organophosphates followed by carbamates, and the most widely represented bee taxa were bumblebees (Bombus), followed by leaf-cutter bees (Megachile) and mason bees (Osmia). Research has taken place across several countries, with the highest numbers of articles from Brazil and the US, and with notable gaps from countries in Asia, Africa and Oceania. Mortality was the most studied effect type, while sub-lethal effects such as on behaviour were less studied. Few studies tested how insecticides were influenced by other multiple pressures, such as climate change and co-occurring pesticides (cocktail effects). As anthropogenic pressures do not occur in isolation, we suggest that future research also addresses these knowledge gaps. Given the changing global patterns in insecticide use, and the increasing inclusion of both non-honeybees and sub-lethal effects in pesticide risk assessment, there is a need for expanding research beyond its current state to ensure a strong scientific evidence base for the development of risk assessment and associated policy.
... The neonicotinoid class of insecticides is the most efficient at controlling sucking pests, such as aphids, whiteflies, leafhoppers and planthoppers, thrips, several of the micro-lepidoptera, and some coleopteran pests. The multiple functions of these insecticides are derived from their physicochemical properties, which allow different modes of application of these insecticides, including foliar and stem application, seed treatment, and soil drench (Rouchaud et al., 1994;Nauen et al., 2003;Elbert et al., 2008). Nitenpyram, a second-generation neonicotinoid family pesticide, marketed in 1995, is characterized by its relatively low mammalian toxicity and no apparent long-term cumulative effects (Veeranagouda et al., 2006;Sun et al., 2013). ...
Nitenpyram is a neonicotinoid insecticide that is commonly found in the environment. However, its biodegradation by pure cultures of bacteria has not been widely investigated and the catabolic pathway (s) for nitenpyram metabolism remain elusive. In this study, the aerobic strain DF-1, isolated from a wastewater-treatment pool contaminated with nitenpyram. The strain was designated an Ochrobactrum sp. utilizing a combination of traditional methods and molecular ones. Strain DF-1 can use nitenpyram as a sole carbon or nitrogen source for growth. In liquid medium, 100 mg·L ⁻¹ nitenpyram was metabolized to undetectable levels within 10 days. Four metabolites were found by gas chromatography–mass spectrometry (GC–MS) analyses during nitenpyram degradation. According to the aforementioned data, a partial metabolic pathway of nitenpyram was proposed of strain DF-1. Inoculation of strain DF-1 promoted nitenpyram (10 mg·kg ⁻¹ ) degradation in either sterile or non-sterile soil. To our knowledge, this is the first characterization of nitenpyram degradation by a specific bacterium and likely to be exploited for the remediation of nitenpyram-contaminated sites.
... In contrast to B. bassiana treatments, application of dinotefuran from the ground and from helicopters significantly reduced L. delicatula abundance. Foliar sprays tested here are well suited for application of dinotefuran, which is translocated through plants after penetrating leaves (Elbert et al. 2008). The success of aerial applications demonstrates the potential for such methods to be integrated into ongoing management efforts aimed at slowing the spread of L. delicatula. ...
Management to control the spotted lanternfly, Lycorma delicatula (White), would ideally achieve managers' goals while limiting impacts on nontarget organisms. In a large-scale field study with 45 plots at least 711 m2, we tested foliar applications of dinotefuran and 2 formulations of Beauveria bassiana (Balsamo) Vuillemin, each applied from the ground and separately by helicopter. Applications targeted early instar nymphs. For both application methods, a single treatment with dinotefuran significantly reduced L. delicatula numbers, as measured by catch on sticky bands (91% reduction by air and 84% reduction by ground 19 days after application) and by timed counts (89% reduction by air and 72% reduction by ground 17 days after application). None of the B. bassiana treatments significantly reduced L. delicatula numbers, even after 3 applications. Beauveria bassiana infection in field-collected nymphs ranged from 0.4% to 39.7%, with higher mortality and infection among nymphs collected from ground application plots. Beauveria bassiana conidia did not persist for long on foliage which probably contributed to low population reduction. Nontarget effects were not observed among arthropods captured in blue vane flight intercept traps, San Jose Scale pheromone sticky traps or pitfall traps, but power analysis revealed that small reductions of less than 40% may not be detected despite extensive sampling of 48,804 specimens. These results demonstrate that dinotefuran can markedly reduce local abundance of L. delicatula with little apparent effect on nontarget insects when applied shortly after hatch, and that aerial applications can match or exceed the effectiveness of applications from the ground.
... From the 2000 s, researchers focused on the mechanisms of selective action by determining their structures, binding site targets, and pharmacodynamic properties (Jeschke and Nauen, 2008;Tomizawa and Casida, 2005). NEOs, with high effectiveness, were increasingly applied to control pests resistant to conventional pesticides (Nauen and Denholm, 2005), disease vectors, and seed treatment (Elbert et al., 2008;Jeschke et al., 2011). ...
Neonicotinoids (NEOs) are synthetic insecticides with broad-spectrum insecticidal activity and outstanding efficacy. However, their extensive use and persistence in the environment have resulted in the accumulation and biomagnification of NEOs, posing significant risks to non-target organisms and humans. This review provides a summary of research history, advancements, and highlighted topics in NEOs remediation technologies and mechanisms. Various remediation approaches have been developed, including physiochemical, microbial, and phytoremediation, with microbial and physicochemical remediation being the most extensively studied. Recent advances in physiochemical remediation have led to the development of innovative adsorbents, photocatalysts, and optimized treatment processes. High-efficiency degrading strains with well-characterized metabolic pathways have been successfully isolated and cultured for microbial remediation, while many plant species have shown great potential for phytoremediation. However, significant challenges and gaps remain in this field. Future research should prioritize isolating, domesticating or engineering high efficiency, broad-spectrum microbial strains for NEO degradation, as well as developing synergistic remediation techniques to enhance removal efficiency on multiple NEOs with varying concentrations in different environmental media. Furthermore, a shift from pipe-end treatment to pollution prevention strategies is needed, including the development of green and economically efficient alternatives such as biological insecticides. Integrated remediation technologies and case-specific strategies that can be applied to practical remediation projects need to be developed, along with clarifying NEO degradation mechanisms to improve remediation efficiency. The successful implementation of these strategies will help reduce the negative impact of NEOs on the environment and human health.
... As with many plant pests, the most commonly used method of controlling aphids is also chemical control. Therefore, with the intensive usage of synthetic insecticides, aphids have developed stronger resistance to many insecticides over time (Elbert et al., 2008). As a result of excessive use of insecticides, the ...
In this study, the effect of methanol extracts of three different genotypes (Narlısaray, Kavacık, Maltepe) of Cannabis sativa L. on Diuraphis noxia Kurdjumov, Myzus persicae (Sulzer) and Aphis fabae (Scopoli) (Hemiptera: Aphididae) were investigated. In the first stage of the study, 10% concentrations of each cannabis extract were applied on the 2nd and 3rd nymphal stages of aphid species by spraying method. After the end of 24 - 48 and 72 hours of the applications, the alive and dead individuals were recorded and mortality rates were determined. In the second stage, the genotype with the highest effect was used in dose-death trials and LD50 and LD90 values at different doses (2.5%, 5%, 7.5% and 10%) were specified. In the census after 72 hours, Narlısaray genotype showed the highest mortality rate with 54.04% on D. noxia. While the effect of Kavacık genotype on M. persicae was found as 23.13%, the highest toxicity record of the same genotype was determined on A. fabae (as 91.76%). According to the dose measurement studies of Kavacık genotype on A. fabae, LD50 and LD90 values were calculated to be 0.33 and 0.110 (mg/individual), respectively. At the results of study, it has been observed that extracts of different genotypes of the industrial cannabis plant are found effective on aphid species and it is thought that they can be used in controlling of these pests.
... The risk is also compounded by the fact that birds prefer to feed at the field borders, where the density sown of seeds remaining on the soil surface is usually greater, compared with the center of the field (Lennon et al. 2020;Lopez-Antia et al. 2016;Prosser 1999). The systemic properties of neonicotinoids insecticides make them suitable to be used in seed treatment, as the active ingredient is taken up by the seedling from the seed, protecting the growing plant against sucking pests (Elbert et al. 2008;Simon-Delso et al. 2015). As neurotoxic agents, neonicotinoids act in the pest insect by binding to the postsynaptic nicotinic receptors causing paralysis and death (Yamamoto and Casida 1999). ...
Neonicotinoids are globally used insecticides, and there are increasing evidence on their negative effects on birds. This study is aimed at characterizing the behavioral and physiological effects of the neonicotinoid imidacloprid (IMI) in a songbird. Adults of Agelaioides badius were exposed for 7 days to non-treated peeled millet and to peeled millet treated with nominal concentrations of 75 (IMI1) and 450 (IMI2) mg IMI/kg seed. On days 2 and 6 of the trial, the behavior of each bird was evaluated for 9 min by measuring the time spent on the floor, the perch, or the feeder. Daily millet consumption, initial and final body weight, and physiological, hematological, genotoxic, and biochemical parameters at the end of exposure were also measured. Activity was greatest on the floor, followed by the perch and the feeder. On the second day, birds exposed to IMI1and IMI2 remained mostly on the perch and the feeder, respectively. On the sixth day, a transition occurred to sectors of greater activity, consistent with the disappearance of the intoxication signs: birds from IMI1 and IMI2 increased their time on the floor and the perch, respectively. Control birds always remained most of the time on the floor. IMI2 birds significantly decreased their feed intake by 31% the first 3 days, compared to the other groups, and significantly decreased their body weight at the end of the exposure. From the set of hematological, genotoxic, and biochemical parameters, treated birds exhibited an alteration of glutathione-S-transferase activity (GST) in breast muscle; the minimal effects observed are probably related to the IMI administration regime. These results highlight that the consumption of less than 10% of the bird daily diet as IMI-treated seeds trigger effects at multiple levels that can impair bird survival.
... They are usually used to suppress populations of sucking arthropods, such as aphids and leafhoppers (Oliveira et al. 2008;Magalhães et al. 2009;Krupke et al. 2017;Ding et al. 2018). Some characteristics that popularized the use of neonicotinoids are their systemic nature, efficiency at low doses, and relatively low toxicity to mammals (Elbert et al. 2008;Goulson 2013 However, despite their advantages, neonicotinoid insecticides can negatively affect beneficial insect populations and contribute to pest outbreaks. For example, neonicotinoids applied through seed treatment can cause lethal and sublethal effects on beneficial organisms that feed on plant resources such as pollen, floral and extrafloral nectar, and sap (Moscardini et al. , 2015Gontijo et al. 2014Gontijo et al. , 2018Rundlöf et al. 2015;Sâmia et al. 2019;Wu et al. 2021). ...
Neonicotinoid seed treatment (NST) is a routine practice used worldwide to control insect pests in a variety of crops, including maize (Zea mays mays L.). However, previous work indicates that systemic insecticides can compromise plant defenses, counteracting efforts to control insect pests. The goal of this study was to evaluate the effect of thiamethoxam-neonicotinoid seed treatment on the resistance of two maize genotypes (B73 and MC 4050) against the major non-target pest, fall armyworm Spodoptera frugiperda (Lepidoptera: Noctuidae). In preference and performance assays, we evaluated the effect of NST on fall armyworm behavior and biology. We also determined the influence of NST on induced plant defenses, quantifying phytohormone levels and plant volatile emissions, in treatments with and without fall armyworm herbivory. NST did not affect caterpillar host preference, however it reduced caterpillar performance on the genotype B73 across both maize growth stages (V4 and V6). NST-treated B73 plants also had lower induced volatile production (V4 stage) compared to untreated herbivore-damage plants and lower constitutive salicylic acid (V6 stage). In contrast, MC 4050 was not affected by the insecticide, regardless of growth stage. In conclusion, we found that the effects of NST on maize defenses vary by plant genotype and growth stage, suggesting growers may need to tailor their selection of plant genotypes to avoid negative impacts of NST on plant resistance and ultimately pest control.
... Imidacloprid, a synthetic neonicotinoid insecticide, has been widely used for pest control in various crops due to its broad-spectrum, high efficiency, low toxicity and low residue (Elbert et al. 2008). However, the extensive application of imidacloprid has the potential to adverse influence on ecosystems and human health. ...
In this work, FeS supported SBA-15 mesoporous silica catalyst (FeS@SBA-15) was synthesized successfully, characterized and first applied to persulfate (PS) activation for the degradation of imidacloprid in wastewater. The as-prepared 3.5-FeS@SBA-15 presented an impressive imidacloprid removal efficiency of 93.1% and reaction stoichiometric efficiency (RSE) of 1.82% after 5 min, ascribed to the synergetic effects of improved FeS dispersion and abundant surface sites by SBA-15. Electron paramagnetic resonance spectra and quenching experiments proved that both SO4·- and ·OH were produced in FeS@SBA-15/PS system, and SO4·- played a dominant role in the degradation process. The S²⁻ can accelerate the cycling of Fe(III)/Fe(II) during activation and increase the steady-state concentration of Fe(II). More importantly, the constructed heterogeneous system exhibited an efficient and stable catalytic activity over a wide range of pH (3.0-9.0), temperature (283K-313K), inorganic ion (NO3⁻) and humic acid (1-20 mg/L). Moreover, the density functional theory calculations were conducted to predict the potential reaction sites of imidacloprid. Based on eighteen identified intermediates, four main degradation pathways were proposed: hydroxylation, dechlorination, hydrolysis, and the ring cleavage of the imidazolidine. ECOSAR analysis indicated hydroxylation and dechlorination played a key role in the detoxification of the formed compounds. These findings would provide new insights into the application of FeS@SBA-15 catalyst in wastewater treatment and the removal mechanism of imidacloprid from wastewater.
... Owing to their unique insecticidal action and approved effect, neonicotinoids are widely welcomed by the international pesticide market. Imidacloprid and thiamethoxam, representatives of neonicotinoids, could efficaciously control a variety of sucking insect pests (Bass et al., 2015;Elbert et al., 2008). Naturally, the excessive use of neonicotinoids has brought many events of neonicotinoid resistance in B. tabaci (Dennehy et al., 2010;Wang et al., 2010;Zheng et al., 2017;Wang et al., 2020a;Wang et al., 2020c;Du et al., 2021). ...
High level resistance for a variety of insecticides has emerged in Bemisia tabaci, a globally notorious insect. Neonicotinoid insecticides have been applied widely to control B. tabaci. Whether a differentially expressed gene CYP6DB3 discovered from transcriptome data of B. tabaci is involved in the resistance to neonicotinoid insecticides remains unclear. In the study, CYP6DB3 expression was significantly up-regulated in both thiamethoxam- and imidacloprid-resistant strains relative to the susceptive strains. We also found that CYP6DB3 expression was up-regulated after B. tabaci adults were exposed to thiamethoxam and imidacloprid. Moreover, knocking down CYP6DB3 expression via feeding corresponding dsRNA significantly reduced CYP6DB3 mRNA levels by 34.1%. Silencing CYP6DB3 expression increased the sensitivity of B. tabaci Q adults against both thiamethoxam and imidacloprid. Overexpression of CYP6DB3 gene reduced the toxicity of imidacloprid and thiamethoxam to transgenic D. melanogaster. In addition, metabolic studies showed that CYP6DB3 can metabolize 24.41% imidacloprid in vitro. Collectively, these results strongly support that CYP6DB3 plays an important role in the resistance of B. tabaci Q to imidacloprid and thiamethoxam. This work will facilitate a deeper insight into the part of cytochrome P450s in the evolution of insecticide resistance and provide a theoretical basis for the development of new integrated pest resistance management.
... The neonicotinoids, the newest major class of insecticides, have outstanding potency and systemic action for crop protection against piercing-sucking pests (Tomizawa and John 2005). Neonicotinoids are among the most effective insecticides for the control of sucking insect pests such as aphids, whiteflies, leaf and planthoppers, thrips, some micro lepidoptera and a number of coleopteran pests (Elbert et al 2008) but are less toxic to natural enemies (Akhtar et al 2021). Nitenpyram and imidacloprid was found to be effective against A. fabae (Table 2, Table 3). ...
Faba bean (Vica faba L.) is important crop of Nepal which is grown in all suitable climatic zone of the country. Different insect pests attack faba bean but black bean aphid, Aphis fabae Scop. (Hemiptera: Aphididae) is of more concern. Most of the farmers shifted to another crop due to A. fabae problem. Different insecticides have been sprayed to manage this aphid but most of the farmer were unable to control it. However, very limited research were conducted for its ecofriendly management. Thus, we evaluate different insecticides such as nitenpyram, flonicamid, imidacloprid, dimethoate, azadirachtin, and neem oil on laboratory. Scintillating glass vial test and filter paper test were employed. Higher number of aphid mortality were found on dimethoate with LT 50 value of 15.93 hour followed by nitenpyram, and imidacloprid with 18.61 and 32.87 hour, respectively on scintillating glass vial test. On filter paper test, LT 50 of dimethoate was 27.34 hour followed by imidacloprid and nitenpyram with 49.51 and 53.44, respectively. Similarly, higher lady bird beetle Coccinella septempunctata Linn (Coleoptera: Coccinellidae) mortality were also caused by dimethoate with LT 50 value of 63.38 hour followed by imidacloprid and nitenpyram with 153.21 188.42 hour. Our result suggested that nitenpyram or imidacloprid could be used for ecofriendly management of A. fabae with low mortality of its predator C. septempunctata. However precautionary measure has to be taken before applying pesticides and waiting period has to be maintained for harvesting.
... Studies on the effects of neonicotinoids on gene expression in different plant species have shown a variety of responses, including a decrease in the expression of cell wall synthesis-related genes, which may lead to lower resistance to cell-content feeder insects, and an increase in the expression of (1) photosynthesis-related genes, which may prolong the energy production period, (2) pathogenesis-related genes and (3) stress tolerance-related genes (e.g. genes involved in tolerance to drought and cold) [32][33][34][35]. However, these changes are not consistent, and their mechanisms are unknown [36,37]. ...
Neonicotinoids, a class of systemic insecticides, have been widely used for decades against various insect pests. Previous studies have reported non-target effects of neonicotinoids on some beneficial macro- and micro-organisms. Considering the crucial role the soil microbiota plays in sustaining soil fertility, it is critical to understand how neonicotinoid exposure affects the microbial taxonomic composition and gene expression. However, most studies to date have evaluated soil microbial taxonomic compositions or assessed microbial functions based on soil biochemical analysis. In this study, we have applied a metatranscriptomic approach to quantify the variability in soil microbial gene expression in a 2 year soybean/corn crop rotation in Quebec, Canada. We identified weak and temporally inconsistent effects of neonicotinoid application on soil microbial gene expression, as well as a strong temporal variation in soil microbial gene expression among months and years. Neonicotinoid seed treatment altered the expression of a small number of microbial genes, including genes associated with heat shock proteins, regulatory functions, metabolic processes and DNA repair. These changes in gene expression varied during the growing season and between years. Overall, the composition of soil microbial expressed genes seems to be more resilient and less affected by neonicotinoid application than soil microbial taxonomic composition. Our study is among the first to document the effects of neonicotinoid seed treatment on microbial gene expression and highlights the strong temporal variability of soil microbial gene expression and its responses to neonicotinoid seed treatments.
... The widespread use of synthetic chemicals like pesticides, particularly neonicotinoids, is considered one of the most determinant factors in the decline of pollinator populations worldwide (Rundlöf et al., 2015;Janousek et al., 2023). Neonicotinoids are the most widely used pesticides globally and are used to control a variety of sucking pests (Elbert et al., 2008;Xu et al., 2022). Residues of these insecticides have been found not only in soil (Liu Z. K. et al., 2022) and water (Mahai et al., 2019) but have also been traced in the pollen and nectar due to their systemic properties (Singla et al., 2020;Alkassab et al., 2023) and can harm non-target pollinator honeybees by acting on nicotinic acetylcholine receptors (nAChRs) in the insects' nervous system (Tomizawa and Casida, 2003) and nonneuronal ACh system (Grunewald and Siefert, 2019). ...
The use of agricultural neonicotinoid insecticides has sub-lethal chronic effects on bees that are more prevalent than acute toxicity. Among these insecticides, thiacloprid, a commonly used compound with low toxicity, has attracted significant attention due to its potential impact on the olfactory and learning abilities of honeybees. The effect of sub-lethal larval exposure to thiacloprid on the antennal activity of adult honeybees ( Apis mellifera L.) is not yet fully understood. To address this knowledge gap, laboratory-based experiments were conducted in which honeybee larvae were administered thiacloprid (0.5 mg/L and 1.0 mg/L). Using electroantennography (EAG), the impacts of thiacloprid exposure on the antennal selectivity to common floral volatiles were evaluated. Additionally, the effects of sub-lethal exposure on odor-related learning and memory were also assessed. The results of this study reveal, for the first time, that sub-lethal larval exposure to thiacloprid decreased honeybee antenna EAG responses to floral scents, leading to increased olfactory selectivity in the high-dose (1.0 mg/L) group compared to the control group (0 mg/L vs . 1.0 mg/L: p = 0.042). The results also suggest that thiacloprid negatively affected odor-associated paired learning acquisition, as well as medium-term (1 h) (0 mg/L vs . 1.0 mg/L: p = 0.019) and long-term memory (24 h) (0 mg/L vs . 1.0 mg/L: p = 0.037) in adult honeybees. EAG amplitudes were dramatically reduced following R-linalool paired olfactory training (0 mg/L vs . 1.0 mg/L: p = 0.001; 0 mg/L vs . 0.5 mg/L: p = 0.027), while antennal activities only differed significantly in the control between paired and unpaired groups. Our results indicated that exposure to sub-lethal concentrations of thiacloprid may affect olfactory perception and learning and memory behaviors in honeybees. These findings have important implications for the safe use of agrochemicals in the environment.
... Similarly, NEOs are highly effective against pest insects, and exposure and effects on invertebrates have been intensely studied (Goulson, 2013). Notably, NEOs were long considered relatively non-toxic to vertebrates (Elbert et al., 2008). However, recent studies documented that NEOs may also accumulate in non-target species such as birds (Distefano et al., 2022a;Humann-Guilleminot et al., 2019, 2021 and small mammals (Fritsch et al., 2022), and have the potential to affect mammalian health after ingestion and prenatal exposure (Burke et al., 2018;Costas-Ferreira and Faro, 2021). ...
Neonicotinoids (NEOs) and active pharmaceuticals ingredients (API) are contaminants widely diffused worldwide, causing increasing concern for potential adverse effects on wildlife. However, research on these contaminants have focused on target and non-target invertebrates, while information on potential effects in terrestrial mammals is lacking. We performed preliminary non-invasive monitoring of NEOs and API in a suburban and agricultural area using hair of the Red fox. The Red fox is a widely diffused mesopredator in Europe, and its plasticity in feeding habits makes it an excellent indicator for assessing exposure to environmental contamination. We observed the presence of NEOs in many Red fox hair samples (n = 11), including imidacloprid (IMI), acetamiprid (ACE), and clothianidin (CLO). The highest quantified concentrations were 6.4 ng g-1 dry weight (dw), 6.7 ng g-1 dw, and 0.9 ng g-1 dw for IMI, ACE, and CLO, respectively. The targeted APIs included non-steroidal anti-inflammatory drugs (NSAIDs) and antidepressants. APIs were less frequently detected than NEOs, and the compounds with the highest prevalence were the NSAID ketoprofen (36%), the antidepressant sertraline (36%), and its active metabolite norsertraline (27%). The presence of human pharmaceuticals such as the NSAID ibuprofen and the antidepressants sertraline, fluoxetine, and their active metabolites norsertraline and norfluoxetine suggest environmental contamination due to untreated and partially treated wastewater discharged in surface waters and soils of the study area. The detection and quantification of ketoprofen and flunixin also suggest the possible use of contaminated manure on farmland. Findings indicate that hair may be used for monitoring environmental exposure to NEOs and provide evidence that hair is a good marker of exposure for antidepressants and certain NSAIDs, including ibuprofen, ketoprofen, and flunixin.
... In the last few decades, they have been the most frequently used insecticides in crop protection due to the broad spectrum of pest control, the relatively low risk to non-target organisms and the environment, and the specificity to target organisms, as well as the versatility of application methods. They are registered in over 120 countries, with a worldwide turnover of EUR 1.5 billion, consisting of 24% of the global insecticide market in 2008 [14][15][16]. ...
This paper presents studies performed for the monitoring of imidacloprid, clothianidin and thiamethoxam residues applied as seed treatment in rapeseed (Brassica napus ssp. oleifera), maize (Zea mays) and sunflower crops (Helianthus annuus). The experiments were located in representative areas of the mentioned crops. Residue levels were determined in plant samples at different pheno-logical development stages, including flowers, as well as in bees and hive products (pollen, honeycomb , honey) by liquid chromatography/tandem mass spectroscopy (LC-MS/MS). The analyses were performed in ISO 17025-accredited laboratories, referring to the limit of quantification (LOQ), characteristic of the method used to determine the residues. In 2019, the percentage of samples that contained residues of the three substances, applied to the seed, was 16.39%, representing 20 samples out of the total of 122 analyzed samples. In 2020, 10 samples contained neonicotinoid residues above the LOQ, including 5 soil samples and 5 plant samples, representing 6.17% of the total samples. In 2021, from 149 samples with neonicotinoid applied as seed treatment, residues were identified in 12 soil samples and 11 plant samples, representing 15.43% of the total number of samples. In 2022, only 12 soil samples and 1 pasture sample contained residues above the LOQ. The results show that the highest percentage of samples with residues above the LOQ was recorded by the soil samples, while the flower and bee samples had the lowest percentages of samples with residues above the LOQ; no residues of the three neonicotinoid substances were identified in the honey samples.
... Although our research group has tested the effect of several sunflower pollen compounds on infection, we have not yet identified any that reduce Crithidia infection in bumble bees [29]. Pesticides are commonly used on sunflower crops to suppress weeds, herbivorous insects and plant pathogens [56] and can pose a substantial risk for bees [57]. The upregulation of multiple detoxification enzymes in sunflower-fed bees could be an indication of pesticide contamination in sunflower pollen. ...
Background
Diet and parasitism can have powerful effects on host gene expression. However, how specific dietary components affect host gene expression that could feed back to affect parasitism is relatively unexplored in many wild species. Recently, it was discovered that consumption of sunflower (Helianthus annuus) pollen reduced severity of gut protozoan pathogen Crithidia bombi infection in Bombus impatiens bumble bees. Despite the dramatic and consistent medicinal effect of sunflower pollen, very little is known about the mechanism(s) underlying this effect. However, sunflower pollen extract increases rather than suppresses C. bombi growth in vitro, suggesting that sunflower pollen reduces C. bombi infection indirectly via changes in the host. Here, we analyzed whole transcriptomes of B. impatiens workers to characterize the physiological response to sunflower pollen consumption and C. bombi infection to isolate the mechanisms underlying the medicinal effect. B. impatiens workers were inoculated with either C. bombi cells (infected) or a sham control (un-infected) and fed either sunflower or wildflower pollen ad libitum. Whole abdominal gene expression profiles were then sequenced with Illumina NextSeq 500 technology.
Results
Among infected bees, sunflower pollen upregulated immune transcripts, including the anti-microbial peptide hymenoptaecin, Toll receptors and serine proteases. In both infected and un-infected bees, sunflower pollen upregulated putative detoxification transcripts and transcripts associated with the repair and maintenance of gut epithelial cells. Among wildflower-fed bees, infected bees downregulated immune transcripts associated with phagocytosis and the phenoloxidase cascade.
Conclusions
Taken together, these results indicate dissimilar immune responses between sunflower- and wildflower-fed bumble bees infected with C. bombi, a response to physical damage to gut epithelial cells caused by sunflower pollen, and a strong detoxification response to sunflower pollen consumption. Identifying host responses that drive the medicinal effect of sunflower pollen in infected bumble bees may broaden our understanding of plant-pollinator interactions and provide opportunities for effective management of bee pathogens.
... A range of synthetic insecticides are extensively used for M. usitatus management, but its high reproduction rate and short generation time have induced the development of insecticide resistance. Acetamiprid, a second-generation nicotinoid insecticide, acts through antagonization of nAChR receptors, thus hindering nerve impulse transmission across the central nervous system of insects (Elbert et al., 2008;Phogat et al., 2022). In recent years, various thrip species (Frankliniella occidentalis, Thrips Scolothrips takahashii, and M. usitatus) have developed resistance to acetamiprid in different regions of the world (Mori and Gotoh, 2001;Chen and Yuan, 2011;Fu et al., 2016;Nazemi et al., 2016;Wang et al., 2016;Han et al., 2017;Zuo et al., 2017;Fu et al., 2019;Lin et al., 2021). ...
Genes of the cytochrome P450 (CYP450) superfamily are known to be involved in the evolution of insecticide resistance. In this study, the transcriptomes of two Megalurothrips usitatus Bagnall (Thysanoptera: Thripidae) strains (resistant and susceptible) were screened for detoxification genes. MusiDN2722 encodes a protein composed of 504 amino acid residues with a relative molecular mass of 57.3 kDa. Multiple sequence alignment and phylogenetic analysis showed that MusiDN2722 is a member of the CYP450 family and has characteristics of the conserved CYP6 domain shared by typical CYP450 family members. RT-qPCR (real-time quantitative polymerase chain reaction) analysis showed that MusiDN2722 was upregulated in the acetamiprid-resistant strain compared with the susceptible strain ( p < 0.05), and the relative expression level was significantly higher at 48 h after exposure than at 24 h after exposure. The interference efficiency of the injection method was higher than that of the membrane-feeding method. Silencing of MusiDN2722 through RNA interference significantly increased the sensitivity of M. usitatus to acetamiprid. Overall, this study revealed that MusiDN2722 plays a crucial role in the resistance of M. usitatus to acetamiprid. The findings will not only advance our understanding of the role of P450s in insecticide resistance but also provide a potential target for the sustainable control of destructive pests such as thrips.
... The control of R. padi mainly relies on the application of chemical insecticides, such as imidacloprid, thiamethoxam, acetamiprid and pyrethroids (Zuo et al., 2016;Kirkland et al., 2018). Thiamethoxam is a commercial neonicotinoid insecticide which acts by binding to nicotinic acetylcholine receptors (nAChRs) and is widely used to control a broad range of important pests, such as aphids, whiteflies, jassids and thrips (Maienfisch et al., 2001;Elbert et al., 2008). The constant and extensive use of insecticides had caused resistance of R. padi to various insecticides (Wang et al., 2020;Gong et al., 2021;Wang et al., 2022). ...
Rhopalosiphum padi (L.) is an important cosmopolitan pest of cereal crops. Thiamethoxam is widely used for control R. padi in some regions. Chemosensory proteins (CSPs) are a class of transporter proteins in arthropods which play a key role in various physiological processes including response to insecticide exposure. However, the role of R. padi CSPs (RpCSPs) in insecticide binding and susceptibility has not been well clarified. In this study, we found that the expression levels of RpCSP1, RpCSP4, RpCSP5, RpCSP7, RpCSP10 were dramatically upregulated after exposure to thiamethoxam. Suppression of RpCSP4 and RpCSP5 transcription by RNA interference significantly enhanced the susceptibility of R. padi to thiamethoxam. Molecular docking and fluorescence competitive binding showed that RpCSP4 and RpCSP5 had high binding affinity with thiamethoxam. The present results prove that RpCSP4 and RpCSP5 are related to insecticide resistance through high binding affinity to reduce the toxicity of insecticide.
... [7] Other reasons that make them successful in agriculture are their long-lasting effects and versatility in application. [8] Due to their physicochemical properties such as relatively small molecular weight, high solubility in water and systemic nature, they can be easily taken up through the roots and leaves protecting it during growth. [7,9] However, due to their widespread and persistence, these substances can be found in all environmental compartments including soil, water, and air, staying for a long time after application, which can have serious adverse impacts in ecosystems. ...
Neonicotinoids (NNIs) are neuro-active and systemic insecticides widely used to protect crops from pest attack. During the last decades, there has been an increase concern about their uses and toxic effects, especially to beneficial and non-target insects such as pollinators. To assess potential health hazards and the environmental impacts derived from NNIs uses, a great variety of analytical procedures for the determination of their residues and their metabolites at trace level in environmental, biological and food samples have been reported. Due to the complexity of the samples, efficient sample pretreatment methods have been developed, which include mostly clean-up and preconcentration steps. On the other hand, among the analytical techniques used for their determination, high-performance liquid chromatography (HPLC) coupled to ultraviolet (UV) or mass spectrometry (MS) detection is the most widely used, although capillary electrophoresis (CE) has also been employed in the last years, considering some improvements in sensitivity when coupling with new MS detectors. In this review, we present a critical overview of analytical methods based on HPLC and CE reported in the last decade, discussing relevant and innovative sample treatments for the analysis of environmental, food and biological samples.
... Neonicotinoids are a group of insecticides whose use has grown rapidly worldwide (Elbert et al., 2008;Jeschke et al., 2011). They are used to control soil and sucking insects (Elbert et al., 1990). ...
Treated seeds and their cotyledons can present a toxicological risk to seed-eating birds. To assess whether avoidance behavior limits exposure and consequently the risk to birds, three fields were sown with soybeans. Half of the surface of each field was sown with seeds treated with 42 g /100 kg seed of insecticide imidacloprid (T plot, treated) and the other half with seeds without imidacloprid (C plot, control). Unburied seeds were surveyed in C and T plots at 12 h and 48 h post-sowing. Damaged seedlings was surveyed in C and T plots at 12 days post-sowing. Abundance and richness of birds was surveyed at the field level (without distinguishing between C and T plots) before, during, and after sowing, and 12 days post-sowing. Seed density was higher in the headlands of the T plots than in the C plots, but did not differ between 12 and 48 h. The damage on cotyledons of seedlings was 15.4% higher in C plots than in T plots. The abundance and richness per hectare of birds that eat seeds and cotyledons were lower after sowing, indicating a deterrent effect of sowing imidacloprid-treated seeds on birds. Although the variation in seed density over time does not allow solid conclusions to be drawn about the avoidance of seeds treated by birds, the seedling results suggest an aversive effect of imidacloprid-treated soybeans on birds. The dominant species was the eared dove (Zenaida auriculata), whose risk of acute poisoning by imidacloprid in soybean seeds and cotyledons was low, according to its toxicity exposure ratio (TER), its foraged area of concern, and its foraged time of concern. This article is protected by copyright. All rights reserved. Environ Toxicol Chem 2023;00:0-0. © 2023 SETAC.
... NNIs are relatively more water-soluble and highly systemic than other groups of contact insecticides, enabling the rapid adsorption and translocation of treated NNIs inside the plant (Sur and Stork 2003). Owing to their systemic properties, NNIs can be treated by various means including not only the typical foliar spray but also seed dressing (coating), soil drenching, and trunk injection, which are particularly effective against sucking pests (Elbert et al. 2008) On the basis of these advantages, NNIs have been the most broadly used class of insecticides worldwide, with seed dressing being the primary application method. Following seed treatment, substantial amounts of NNIs are also taken up by wildflowers growing near arable land and translocated into the pollen and nectar at concentrations that are sometimes even higher than those found in crops (Botías et al. 2015). ...
... (Syngenta Group Company). (17). For the implementation of the study, three different mixing ratios of 1:1, 1:2 and 1:3 (Actara insecticide: Ginger oil), respectively, were used for each of the insecticide Actara concentrations 0.1, 0.15 and 0.2 MgL -1 and Ginger oil (obtained from the local market) diluted with ethanol 1:1 Ginger oil: ethanol and then larvae treated were 3 rd and 5 th instar by spraying method with three replicates and each replicat include 10 larvae of each concentration and the proportion of mixing. ...
... Neonicotinoids, which is one of the most important chemical insecticides, are frequently applied to control sucking pests and several coleopteran, dipteran, and lepidopteran pests. 1 They act selectively against nicotinic acetylcholine receptors (nAChRs) and restrain rapid neurotransmission in insects, ultimately leading to overstimulation of the cholinergic synapse and death of insects. 2 The first commercial neonicotinoid was imidacloprid (IMI), introduced in 1991, after which nitenpyram, acetamiprid, and thiamethoxam (TMX) were launched in the insecticide market. Neonicotinoids have achieved lasting success, given their market share of ∼24%. 3 However, the abuse of insecticides and the associated selection pressure have led to an inevitable increase in resistance to neonicotinoids. ...
... Neonicotinoids, which is one of the most important chemical insecticides, are frequently applied to control sucking pests and several coleopteran, dipteran, and lepidopteran pests. 1 They act selectively against nicotinic acetylcholine receptors (nAChRs) and restrain rapid neurotransmission in insects, ultimately leading to overstimulation of the cholinergic synapse and death of insects. 2 The first commercial neonicotinoid was imidacloprid (IMI), introduced in 1991, after which nitenpyram, acetamiprid, and thiamethoxam (TMX) were launched in the insecticide market. Neonicotinoids have achieved lasting success, given their market share of ∼24%. 3 However, the abuse of insecticides and the associated selection pressure have led to an inevitable increase in resistance to neonicotinoids. ...
Bemisia tabaci has developed high resistance to many insecticides and causes substantial agricultural and economic losses annually. The insecticide resistance of whitefly has been widely reported in previous studies; however, the underlying mechanism remains little known. In this study, we cloned two P450 genes: CYP6DW3 and CYP6DW5v1; these genes were markedly overexpressed in imidacloprid-resistant whitefly populations compared with susceptible populations, and knockdown of these genes decreased the imidacloprid resistance of whitefly. Moreover, heterologous expression of whitefly P450 genes in SF9 cells and metabolic studies showed that the CYP6DW3 protein could metabolize 14.11% imidacloprid and produced imidacloprid-urea in vitro. Collectively, the expression levels of CYP6DW3 and CYP6DW5v1 are positively correlated with imidacloprid resistance in B. tabaci. Our study further reveals that cytochrome P450 enzymes affect the physiological activities related to resistance in insects, which helps scholars more deeply understand the resistance mechanism, and contributes to the development of integrated pest management framework.
... 7,20 They are used in over 120 countries across more than 140 crop types, mostly in the form of seed treatments, foliar sprays and soil/seedling drenches. 20,21 In the United States, for example, 42 million hectares of cropland were sown with neonicotinoidtreated seeds in 2011, equaling 57% of the total area grown to maize, soybean and cotton. 22 Neonicotinoids are widely used in seed treatments due to their systemic nature owing to the moderate to high solubility of these molecules, 23 allowing the active chemical to move through plant tissues. ...
Background:
The prophylactic use of seeds treated with neonicotinoid insecticides remains an important means of controlling aphid pests in canola (Brassica napus) crops in many countries. Yet, one of the most economically important aphid species worldwide, the peach potato aphid (Myzus persicae), has evolved mechanisms which confer resistance to neonicotinoids, including amplification of the cytochrome P450 gene, CYP6CY3. While CYP6CY3 amplification has been associated with low-level resistance to several neonicotinoids in laboratory acute toxicity bioassays, its impact on insecticide efficacy in the field remains unresolved. In this study, we investigated the impact of CYP6CY3 amplification on the ability of M. persicae to survive neonicotinoid exposure under laboratory and semi-field conditions.
Results:
Three M. persicae clones, possessing different copy numbers of CYP6CY3, were shown to respond differently when exposed to the neonicotinoids, imidacloprid and thiamethoxam, in laboratory bioassays. Two clones, EastNaernup209 and Osborne171, displayed low levels of resistance (3-20 fold), which is consistent with previous studies. However, in a large-scale semi-field trial, both clones showed a surprising ability to survive and reproduce on B. napus seedlings grown from commercial rates of neonicotinoid-treated seed. In contrast, an insecticide-susceptible clone, of wildtype CYP6CY3 copy number, was unable to survive on seedlings treated in the same manner.
Conclusion:
Our findings suggest that amplification of CYP6CY3 in M. persicae clones substantially impairs the efficacy of neonicotinoid seed treatments when applied to B. napus. These findings highlight the potentially important real-world implications of resistances typically considered to be 'low level' as defined through laboratory bioassays. This article is protected by copyright. All rights reserved.
... Most neonicotinoids are much less toxic for mammals than insects and thus, they have almost replaced other organophosphate insecticides and more toxic carbamates. Within a decade, such pesticides have gained a 77% share of the market (1). Nowadays, in order to extract the toxins and the residue analysis of the pesticides, a procedure is known as QuEChERS is utilized for extraction as a general method. ...
A Simple and fast QuEChERS method has been applied for extraction of imidacloprid from human biological samples. Imidacloprid the was extracted from blood and liver of a deceased body admitted to the legal Medicine of Mazandaran. Factors affecting the extraction procedure such as type of the organic solvent and its volume, amount of salt, amount of sorbent, and pH were examined and optimized for the maximum recovery. The appropriate condition for extraction of imidacloprid was as follows: sample pH=5, 3mL of acetonitrile, 0.1 g of NaCl, and 0.4 g of MgSO4. The maximum recovery of imidacloprid at these conditions was 96%. The LOD and LOQ were 0.02 and 0.06 ppm, respectively. Finally, the blood and liver samples were extracted under the appropriate condition and determined using HPLC which is equipped with a photodiode array detector. The amounts of Imidacloprid in blood and liver samples were 11 and 1.8 ppm, respectively.
... They are sap-sucking pests, vectors of economically important phytopathogen viruses leading to serious yield losses in various productive cash crops (e.g., sugar beet, sugar cane, potato and wheat) [1,2]. Control of aphids has predominantly relied on the application of synthetic pesticides, including neonicotinoids [3][4][5]. This practice has generated increasing concern due to the adverse effects on pollinators and other nontarget organisms [6][7][8]; the environment by contaminating all types of soils, including grassland sites [9]; and resistance development among aphid colonies [10]. ...
Entomopathogenic fungi (EPF) are cosmopolitan species of great interest in pest management due to their ability to cause epizooty in soil-dwelling and aboveground insects. Besides their direct effect against a wide host range of serious agricultural insect pests, such as aphids, a major emphasis has been placed on investigating the impact of EPF with endophytic traits (EIPF) on aboveground tripartite interactions between host plants, herbivores and beneficial insects. However, despite their valuable role in biocontrol processes, there is still more to explore about their diverse potential as ecofriendly biological control agents. Herein, we provide an overview of the meaningful role and faced challenges following the use of EPF and EIPF to control aphids.
Understanding the mechanism of long-lasting control efficacy of pesticides is important for developing sustainable high-efficacy pesticides, decreasing pesticide-use frequency and environmental input. This study investigates the long-term control mechanism of imidacloprid against wheat aphids under seed treatment. The concentrations of imidacloprid and its metabolites were 2.2-69.6 times lower than their individual LC50 after 238 days of treatment, and the control efficacy was still higher than 94.6%. The mixed bioactivity tests demonstrated that the insecticidal activity of the mixture of imidacloprid and its bioactive metabolites was approximately 1.5-189.7 times greater than that of a single compound against wheat aphids. The concentrations of imidacloprid, 5-hydroxy imidacloprid, and imidacloprid olefin in top flag leaves were 0.022, 0.084, and 0.034 mg/kg, respectively, during the aphid flourishing period, which were higher than the LC50 of the mixture (0.011 mg/kg), therefore providing long-lasting control efficacy. The study provides a first insight into the synergistic effects between a pesticide and its bioactive metabolites in ensuring long-term control performance.
Previous studies to the exposure effects of acetamiprid on honeybees were based on the analysis of bee pollen and honey sacs from field trials or of beebread and honey in the hive, which overestimate or underestimate the risk of exposure to pesticide residues. It was believed that the processing factor (PF) is an important variable to determine the final pesticide residue during royal jelly formation and the actual risk to honeybee larva. Hence, a QuEChERS method to determine acetamiprid contents in honeybee samples was established in this study. Then, the PFs for acetamiprid in beebread fermentation, honey brewing, and royal jelly formation were determined to be 0.85, 0.76, and 0.16, respectively. The PF for royal jelly formation was 0.04 when acetamiprid was detected in beebread alone, and it was 0.12 when acetamiprid was only detected in honey. Finally, the predicted exposure concentration of acetamiprid in royal jelly was calculated to be 2.05 µg/kg using the PF without significant difference with the 90th percentile value (3.64 µg/kg) in the actual sample. However, the value was 16.62 µg/kg without considering the PF. This study establishes a methodology for the correct evaluation of the risk to bee larva of acetamiprid residues in bee pollen and honey sac contents and the residual levels in royal jelly.
Over the past few decades, inadvertent consequences have stemmed from the intensified use of neonicotinoids in agroecosystems. Neonicotinoid applications can result in both positive (e.g., reduced persistent virus transmission) and negative (e.g., increased host susceptibility) repercussions exhibiting ambiguity for their use in crop production. In soybean, aspects of neonicotinoid usage such as the impact on nonpersistent virus transmission and efficacy against nontarget herbivores have not been addressed. This study evaluated the interaction between the neonicotinoid thiamethoxam and soybean variety and the impact on different pest feeding guilds. Feeding and behavioral bioassays were conducted in the laboratory to assess the effect of thiamethoxam on the mortality and weight gain of the defoliator, Chrysodeixis includens (Walker). Bioassays evaluated impacts dependent and independent of soybean tissue, in addition to both localized and systemic efficacy within the soybean plant. Additionally, using the electrical penetration graph technique (EPG), the probing behavior of 2 piercing-sucking pests, Aphis gossypii Glover and Myzus persicae (Sulzer), was observed. Results from defoliator bioassays revealed thiamethoxam had insecticidal activity against C. includens. Distinctions in thiamethoxam-related mortality between bioassays dependent and independent of soybean tissue (~98% versus ~30% mortality) indicate a contribution of the plant towards defoliator-related toxicity. Observations of defoliator feeding behavior showed a preference for untreated soybean tissue relative to thiamethoxam-treated tissue, suggesting a deterrent effect of thiamethoxam. EPG monitoring of probing behavior exhibited a minimal effect of thiamethoxam on piercing-sucking herbivores. Findings from this study suggest neonicotinoids like thiamethoxam may provide some benefit via insecticidal activity against nontarget defoliators.
Bees are essential pollinators of crops and wild plants and their ability to forage and pollinate are key aspects of their behaviour. Bee populations are under threat, with the use of insecticides a contributing factor. Most research has focused on neonicotinoid insecticides and bee mortality, and little is known about impacts on bee foraging and delivery of pollination services. However, other insecticide classes, such as organophosphates and pyrethroids, are increasingly used globally, but little is known about how these widely used substances may impact bees, particularly non‐honeybees.
We exposed bumblebee Bombus terrestris colonies to field‐relevant doses of a pyrethroid (lambda‐cyhalothrin) and an organophosphate (dimethoate) and investigated sublethal effects on behaviour at the individual and colony level, in addition to pollination service delivery under semi‐field conditions.
We show, for the first time, that exposure to these chemicals impacts the activity and pollen provisioning of bumblebee Bombus terrestris audax colonies, while no short‐term effects on flower handling behaviour or pollination service delivery were detected.
We found that colonies exposed to dimethoate were less active, with 67% fewer bees leaving the colony to forage than control colonies, and of those that returned, 92% fewer returned pollen provisions to the nest. Colonies exposed to lambda‐cyhalothrin did not differ in activity; however, 62% fewer of these bees returned with pollen provisions.
Policy implications . These findings give important insights into how exposure to different classes of insecticides could impact bumblebee activity and their provision of pollen required for colony development. With a focus on neonicotinoids in terms of policy changes regarding insecticides and bees, we show that other insecticide classes should also be re‐examined in relation to their potential risks for pollinators. We confirm the need to improve risk assessment of insecticides to assess sublethal effects, include non‐honeybee species in risk assessment processes and also consider key behaviours such as foraging and interactions with plants.
Neonicotinoids are among the most widely used insecticides in the world and are recognized as a potential cause of pollinator decline. Previous studies have demonstrated that the neonicotinoid thiacloprid has adverse effects on foraging and memory behaviors. However, there is no direct evidence linking thiacloprid-induced neuronal cell damage in the brains of honeybees to learning and memory dysfunction. Adult honeybee (Apis mellifera L.) workers were chronically exposed to sub-lethal concentrations of thiacloprid. We discovered that thiacloprid negatively affected their survival, food consumption, and body weight. In addition, sucrose sensitivity and memory performance were impaired. We evaluated the apoptosis of honeybee brain cells using TUNEL (Terminal deoxynucleotidyl transferase-mediated digoxigenin-dUTP-biotin nick-end labeling) and Caspase-3 assays, which revealed that thiacloprid increases the dose-dependent apoptosis of neurons in the mushroom bodies (MB) and antennal lobes (AL). We also determined the abnormal transcripts of multiple genes, including vitellogenin (Vg), immune system genes (apidaecin and catalase), and memory-associated genes (pka, creb, Nmdar1, Dop2, Oa1, Oa-2R, and Oa-3R). These results indicate that exposure to sublethal concentrations of thiacloprid cause abnormal expression of memory-related genes and apoptosis of brain cells in the AL and MB, which may contribute to the memory disorder induced by thiacloprid exposure.
Synthetic pesticides are used widely in agriculture to protect crops from pests, weeds and disease. However, their use also comes with a range of environmental concerns. One of which is effects of insecticides on non-target organisms such as bees, who provide pollination services for crops and wild plants. This systematic literature review quantifies the existing research on bees and insecticides broadly, and then focuses more specifically on non-neonicotinoid insecticides and non-honeybees. We find that articles on honeybees (Apis sp.) and insecticides account for 80% of all research, with all other bees combined making up 20%. Neonicotinoids were studied in 34% of articles across all bees and were the most widely studied insecticide class for non-honeybees overall, with almost three times as many studies than the second most studied class. Of non-neonicotinoid insecticide classes and non-honeybees; the most studied were pyrethroids and organophosphates followed by carbamates, and the most widely represented bee taxa were bumblebees (Bombus), followed by leaf-cutter bees (Megachile) and mason bees (Osmia). Research has taken place across several countries, with the highest numbers of articles from Brazil and the US, and with notable gaps from countries in Asia, Africa and Oceania. Mortality was the most studied effect type, while sub-lethal effects such as on behaviour were less studied. Few studies tested how insecticides were influenced by other multiple pressures, such as climate change and co-occurring pesticides (cocktail effects). As anthropogenic pressures do not occur in isolation, we suggest that future research also addresses these knowledge gaps. Given the changing global patterns in insecticide use, and the increasing inclusion of both non-honeybees and sub-lethal effects in pesticide risk assessment, there is a need for expanding research beyond current state to ensure a strong scientific evidence base for the development of risk assessment and associated policy.
Neonicotinoid (NN) pesticides have emerged globally as one of the most widely used agricultural tools for protecting crops from pest damage and boosting food production. Unfortunately, some NN compounds, such as extensively employed imidacloprid-based pesticides, have also been identified as likely endangering critical pollinating insects like honey bees. To this end, NN pesticides pose a potential threat to world food supplies. As more countries restrict or prohibit the use of NN pesticides, tools are needed to effectively and quickly identify the presence of NN compounds like imidacloprid on site (e.g., in storage areas on farms or pesticide distribution warehouses). This study represents a proof-of-concept where the colloidal properties of specifically modified gold nanoparticles (Au-NPs) able to engage in the rare intermolecular interaction of halogen bonding (XB) can result in the detection of certain NN compounds. Density functional theory and diffusion-ordered NMR spectroscopy (DOSY NMR) are used to explore the fundamental XB interactions between strong XB-donor structures and NN compounds, with the latter found to possess multiple XB-acceptor binding sites. A fundamental understanding of these XB interactions allows for the functionalization of alkanethiolate-stabilized Au-NPs, known as monolayer-protected gold clusters (MPCs), with XB-donor capability (f-MPCs). In the presence of certain NN compounds such as imidacloprid, the f-MPCs subsequently exhibit visual XB-induced aggregation that is also measured with absorption (UV-vis) spectroscopy and verified with transmission electron microscopy (TEM) imaging. The demonstrated f-MPC-aggregation detection scheme has a number of favorable attributes, including quickly reporting the presence of the NN target, requiring only micrograms of suspect material, and being highly selective for imidacloprid, the most prevalent and most important NN insecticide compound. Requiring no instrumentation, the presented methodology can be envisioned as a simple screening test in which dipping a cotton swab of an unknown powder from a surface in a f-MPC solution causes f-MPCs to aggregate and yield a preliminary indication of imidacloprid presence.
Background
Neonicotinoid insecticides are applied worldwide for the control of agricultural insect pests. The evolution of neonicotinoid resistance has led to the failure of pest control in the field. The enhanced detoxifying enzyme activity and target mutations play important roles in the resistance of insects to neonicotinoid resistance. Emerging evidence indicates a central role of the gut symbiont in insect pest resistance to pesticides. Existing reports suggest that symbiotic microorganisms could mediate pesticide resistance by degrading pesticides in insect pests.
Results
The 16S rDNA sequencing results showed that the richness and diversity of the gut community between the imidacloprid-resistant (IMI-R) and imidacloprid-susceptible (IMI-S) strains of the cotton aphid Aphis gossypii showed no significant difference, while the abundance of the gut symbiont Sphingomonas was significantly higher in the IMI-R strain. Antibiotic treatment deprived Sphingomonas of the gut, followed by an increase in susceptibility to imidacloprid in the IMI-R strain. The susceptibility of the IMI-S strain to imidacloprid was significantly decreased as expected after supplementation with Sphingomonas. In addition, the imidacloprid susceptibility in nine field populations, which were all infected with Sphingomonas, increased to different degrees after treatment with antibiotics. Then, we demonstrated that Sphingomonas isolated from the gut of the IMI-R strain could subsist only with imidacloprid as a carbon source. The metabolic efficiency of imidacloprid by Sphingomonas reached 56% by HPLC detection. This further proved that Sphingomonas could mediate A. gossypii resistance to imidacloprid by hydroxylation and nitroreduction.
Conclusions
Our findings suggest that the gut symbiont Sphingomonas, with detoxification properties, could offer an opportunity for insect pests to metabolize imidacloprid. These findings enriched our knowledge of mechanisms of insecticide resistance and provided new symbiont-based strategies for control of insecticide-resistant insect pests with high Sphingomonas abundance.
The mosaic leafhopper, Orientus ishidae (Matsumura), is an Asian species widespread in Europe that can cause leaf damage in wild trees and transmit disease phytoplasmas to grapevines. Following an O. ishidae outbreak reported in 2019 in an apple orchard in northern Italy, the biology and damage caused by this species to apples were investigated during 2020 and 2021. Our studies included observations on the O. ishidae life cycle, leaf symptoms associated to its trophic activity, and its capability to acquire “Candidatus Phytoplasma mali,” a causal agent of Apple Proliferation (AP). The results indicate that O. ishidae can complete the life cycle on apple trees. Nymphs emerged between May and June, and adults were present from early July to late October, with the peak of flight between July and early August. Semi-field observations allowed for an accurate description of leaf symptoms that appeared as a distinct yellowing after a one-day exposure. In field experiments, 23% of the leaves were found damaged. In addition, 16–18% of the collected leafhoppers were found carrying AP phytoplasma. We conclude that O. ishidae has the potential to be a new apple tree pest. However, further studies are required to better understand the economic impact of the infestations.
This book presents the current approaches for insect pest control as a "green" alternative to classical and more toxaic agrochemicals. An overview of the recent advances in insecticide chemistry is also included, which will be of interest to a vast group of researchers - agrochemists, biochemists, chemists and toxicologists. The combination of both chemical and toxicological aspects of insecticides is unique and the book includes contributions from synthetic chemists, entomologists, environmentalists and toxicologists giving it wide appeal. Throughout the book, the different approaches that involve "greener chemicals" are emphasized. The book is divided into 9 chapters, each considering the state of art of each family of insecticides, together with future expectations. Each chapter gives a description of useful biorational insecticides, highlighting environmentally-friendly processes and then the mode of action is fully-described, emphasizing selectivity towards targeted species. Finally, for every family of compounds, their environmental effects (toxicity, bioaccumulation and metabolism) is considered, comparing them to classical insecticides, including human and environmental risk assessments. In addition the formulation, dispersal and persistence in the environment are covered as key aspects in developing greener agrochemicals. The book also includes a general introduction to entomology, with special emphasis on those insects that act as vectors in the spread of diseases. Insects that may be potential pests against humans and livestock are included, focusing on their life cycles, and physiology, as a logical comprehension of mode of action of insecticides. In addition there is a chapter on classical insecticides (covering both, approaches prior to the chemical era, and classical chemical insecticides, organochlorinated, organophosphorus, and carbamates) for comparison with current trends in pest control. The negative environmental effects that such insecticides have caused in nature, such as poisonings, bioaccumulation or toxic effects are highlighted. It is hoped that the use of more specific agrochemicals and approaches may avoid, or at least considerably reduce such severe and irreversible effects in nature. The insecticides covered are considered from numerous points of views: chemistry, toxicological profile, risk assessment, legal status, environmental behaviour and selectivity. The most important families of currently used insecticides are covered and critical discussions about future perspectives are included with frequent comparisons to classical insecticides. The following topics are covered in the book, as greener alternatives to classical insecticides: " Pyrethrins and pyrethroids " Neonicotinoids " Spynosins " Insect growth regulators " Botanical insecticides " Microbial insecticides " Integrated Pest Management Programs (IPM)
Background:
The amino acids R and S proline were used to synthesize novel neonicotinoid derivatives which after being characterized by 1 H, DEPTQ 135, and HRMS-QTOF, were evaluated as insecticides against Galleria mellonela (caterpillar), Sitophilus Zeamais, Xylosandrus morigerus, Xyleborus affinis, and Xyleborus ferrugineus.
Results:
The comparison between biological activity and absolute configuration showed that the R enantiomer has an excellent and outstanding insecticidal activity against the insects with up to 100% mortality after 12 hours when compared to dinotefuran at the same concentration.
Conclusions:
The results suggest that compound R6 can be an excellent lead enantiopure insecticide for future development in the field of crop protection. Furthermore, intermolecular interactions between nicotinic acetylcholine receptors and the R enantiomer display a lower score and π - π interactions more stable than the S derivative. This article is protected by copyright. All rights reserved.
PurposeNeonicotinoids are currently the most common type of insecticide used worldwide for agricultural purposes. However, their strong and deleterious effects on nontarget organisms such as soil biota have motivated several countries to reevaluate the use of neonicotinoids. Effects of neonicotinoids on arbuscular mycorrhizal fungi (AMF) as nontarget organisms remain poorly understood, despite the crucial importance of these microorganisms for soil community structure, plant productivity, and crop yield.Methods
We evaluated increased concentrations of two insecticides (imidacloprid and thiamethoxam) on spore germination of two AMF species (Rhizophagus clarus and Gigaspora albida) using tropical artificial soil. Concentrations of both insecticides were 0, 10, 50, 100, 250, 500, 750, and 1000 mg a.i. kg−1 of a dry substrate with 14 days of incubation.ResultsSpore germination of both species was reduced even by the lowest imidacloprid concentration (10 mg a.i. kg−1). At the highest concentration tested (1000 mg a.i. kg−1), germination of G. albida was 90.2% inhibited, whereas for R. clarus this value was 62.0%. Regarding thiamethoxam, spore germination of G. albida was reduced by 42.9% was 42.9% at the highest concentration evaluated, and R. clarus was 69.1%.Conclusion
Due to low rates of exposure and toxicity response, no potential risk can be predicted for spore germination inhibition. However, reduced spore germination may impact symbiosis development and mycorrhizal effectiveness, and therefore, these possible consequences should be further explored.
Pesticide pollution is an arduous challenge encountered in the field of industrial wastewater treatment. As a Fenton-like metal catalyst, multifunctional biochar has attracted more and more attention in the dissolution of insoluble organic chemical pollutants. In this study, the magnetic municipal sludge biochars(MSDBC)were synthesized by one-step pyrolysis of sludge from sewage treatment plant. The biochars prepared at different temperatures have great differences in surface functional groups and composition of iron phase. MSDBC prepared at 400 °C has a better catalytic oxidation capacity, while MSDBC prepared at 800 °C has a stronger adsorption capacity. The reason is that the morphology and iron phase composition distribution of biochar are different. More pore structures were formed on the surface of biochar prepared at 800 °C, which not only has better adsorption performance, but also makes the impregnated Fe³⁺ enter the interior of biochar and transform during pyrolysis. However, the iron phase of MSDBC prepared at 400 °C is mostly located on the surface and the content of Fe²⁺ is higher. Notably, iron compounds embedded in the magnetic biochar have been proved to be the main catalysts for activating hydrogen peroxide (H2O2) to produce hydroxyl radicals (·OH). Radical quenching experiment and electron paramagnetic resonance (EPR) detection confirmed the production of ·OH and its important role in the oxidative degradation of thiamethoxam (THX). In the THX degradation, MSDBC/H2O2 Fenton-like system showed excellent effect at neutral pH environment. Finally, the innovative use of MSDBC/H2O2 Fenton-like technology in the degradation of complex actual wastewater showed good practicability and stability. This research provides a new idea for the treatment of pesticide wastewater.
Neonicotinoids can control crop pests with high efficiency and low cost and have quickly swept one-fourth of the global insecticide market since the launch of imidacloprid in 1991. Imidacloprid and acetamiprid, the first generation of neonicotinoids, and dinotefuran, the representative of third generation of neonicotinoids, were applied on tomato plants individually to investigate neonicotinoid effects on tomato fruit quality, especially on appearance parameters, sugar, acid, and aroma compounds. Compared with the control, fewer differences in the transcriptome profile, sugar, acid, and volatile organic compound (VOC) contents, and sensory analysis results were shown in dinotefuran treatments than in the other two treatments. Therefore, dinotefuran was more recommended to control pests of tomatoes with less loss of fruit flavor and quality as well as lower ecological risks.
Adult Bemisia tabaci (Gennadius) were tested with imidacloprid in a bioassay method using systemically treated cotton leaves. The method was simple, robust and repeatable and provided baseline data for a laboratory and a number of recently collected field strains. The LC50 for imidacloprid susceptible strains was calculated to be 1.7 ppm and a concentration of 16 ppm determined as diagnostic for imidacloprid resistance. Ten strains of B. tabaci collected from the Almeria region of Spain showed significantly less mortality at the diagnostic dose than the susceptible strains. The intensive use of imidacloprid in the Almeria region is considered the reason for the occurrence of resistance in this locality. Resistance to organophosphates, pyrethroids and endosulfan in B-type and non-B type B. tabaci did not confer resistance to imidacloprid.
Nitenpyram (Capstar) is a fast acting, orally administered flea treatment that is absorbed into the blood of the host animal and is readily available for uptake by feeding fleas. We examined the efficacy of a single dose of nitenpyram against adult cat fleas, Ctenocephalides felis (Bouché), over several days. We recorded adult flea mortality and flea egg production on treated and untreated cats. Nitenpyram provided 100% kill of all fleas on the host at the time of treatment and for up to 24 h after treatment. Between 24 and 48 h after treatment, there was a 98.6% reduction in adult flea numbers. From 48 to 72 h, there was a 5% reduction in adult fleas. There was a 97% reduction and 95.2% reduction in the number of flea eggs collected from treated versus untreated animals during the first 48 h and from 48 to 72 h, respectively. In addition, we quantified three distinct behavioral responses of infested adult cats treated with nitenpyram to determine the extent of any immediate, overt behavioral responses in treated animals. A significant increase in scratching, biting, licking, and twitching occurred for 5 h. The biting and licking continued for 7 h after treatment. Administration of nitenpyram provides an effective mechanism to eliminate adult fleas from hosts for up to 48 h after treatment.
Following the discovery of the insecticidal properties of the heterocyclic nitromethylenes (Soloway et al. 1979), chemists of Nihon Bayer Agrochem started in 1979 to optimize these structures. In 1985, the coupling of the chloropyridyl moiety to the N-nitro substituted imidazolidine ring system enabled the synthesis of the highly active insecticide imidacloprid (Kagabu 1999; Nauen et al. 2001; Jeschke et al. 2002). Imidacloprid is the first commercial example of the neonicotinoid (chloronicotinyl) insecticides acting agonistically on nicotinic acetylcholine receptors (Bai et al. 1991; Elbert et al. 1991; Nauen et al. 2001; Tomizawa and Casida 2003). The insect nicotinic acetylcholine receptor (nAChR) is one of the insecticidal targets which came into vogue after the introduction of the first neonicotinoid (chloronicotinyl) insecticide imidacloprid by Bayer CropScience in 1991, which was reviewed very recently (Nauen et al. 2001). Since the launch of imidacloprid (top-selling insecticide worldwide today), neonicotinoids have developed into a major class of insecticides with several other (commercialized) active ingredients having been described over the last decade and representing some 12% of the insecticide market in 1999 (Nauen and Bretschneider 2002), e.g., acetamiprid (Takahashi et al. 1992), nitenpyram (Minamida et al. 1993), thiamethoxam (Maienfisch and Sell 1992), dinotefuran (Kodaka et al. 1998), thiacloprid (Elbert et al. 2000), and clothianidin (Ohkawara et al. 2002). All neonicotinoid insecticides are effective against sucking insects such as aphids, whiteflies and planthoppers, but also beetles and some lepidopteran pests, such as leaf miners and Cydia pomonella (Elbert and Nauen 1998; Elbert et al. 2000). Although it has been on the market for more than a decade, imidacloprid has proved remarkably resilient to resistance, and only a few geographically localized cases of neonicotinoid resistance have been reported, e.g., Bemisia tabaci in southern Spain (Denholm et al. 2002; Nauen et al. 2002).
1-メチルアミノ-1-[N-メチル-N-(3-ピリジルメチル)]アミノ-2-ニトロエテンがトビイロウンカ, ツマグロヨコバイ, ヒメトビウンカに対して強い活性を示すことを前報で報告した. 本報では3-ピリジル基を他の芳香族複素環に変換し, トビイロウンカに対する活性を検討した. その結果6-クロロ-3-ピリジル, 6-プロモ-3-ピリジル, 6-フルオロ-3-ピリジル, 2-クロロ-5-チアゾリル基を有する化合物は0.5または0.8ppmで100%の死虫率を示したので, 芳香族複素環を6-ハロゲノ-3-ピリジル, 2-クロロ(またはプロモ)-5-チアゾリル基に固定して構造-活性相関を検討した. アミノ基としてはメチルアミノ, ジメチルアミノ, N-ホルミル-N-メチルアミノ基が, 芳香族複素環メチル基が結合した窒素原子の置換基としては水素, メチル, エチル, ホルミル, シクロプロピル基が好ましいことが判明し, 0.5または0.8ppmで100%の死虫率を示す化合物および低濃度での試験を実施しなかった化合物5b-1はさらに評価を行なった. その結果1-[N-(6-クロロ-3-ピリジルメチル)-N-エチル]アミノ-1-メチルアミノ-2-ニトロエテン (5b-8, TI-304, ニテンピラム) が候補化合物として選ばれた.
Following the discovery of the insecticidal properties of the heterocyclic nitromethylenes (Soloway et al. 1978), chemists of Nihon Bayer Agrochem started in 1979 to optimize these structures. In 1985 the coupling of the chloropyridyl moiety to the N-nitro substituted imidazolidine ring system enabled the synthesis of the highly active insecticide imidacloprid (Fig. 1). Imidacloprid is the first commercial example of the chloronicotinyl insecticides acting on nicotinic acetylcholine receptors (Leicht 1993). It is now registered in more than 60 countries as a compound with a new or non-conventional mode of action to combat highly resistant insect pests (Elbert et al. 1991; Elbert et al. 1996; Nauen et al. 1996a). Chloronicotinyl insecticides will grow in importance in the coming years because other close analogues of imidacloprid, such as Takeda’s and Nippon Soda’s open chain derivatives nitenpyram and acetamiprid, respectively, have been described (Tomizawa et al. 1995; Yamamoto et al. 1995). During recent years several studies have demonstrated the excellent activity of imidacloprid on pest species of different orders. The present chapter gives an overview of the biological activity of imidacloprid on different target pests, its selectivity even at the molecular level, its physicochemical properties which led to good systemicity and its agricultural importance.
In the early 1980s, an important discovery was made by Shell researchers when the insecticidal activity of heterocyclic nitromethylene compounds was found (Soloway et al. 1979). After an intensive optimization program, Nithiazin was identified as the most active compound (Figure 1). However, this product was not commercialized. This new chemical class subsequently attracted much attention as a potential tool for insect control, and was taken up by several companies such as Bayer, Takeda, Nippon Soda, Agro Kanesho, Mitsui Toastu and Ciba (since 1996; Novartis).
??-????????????3-?????????????????????????????????????????????????????????????????????????????????????????????, ?????????????????????????????????. 1-(3-?????????????????????) ?????????-2-?????????????????????1??????????????????????????????????????????????????????????????????????????????????????????????????????????????????, ?????????????????????????????????????????????????????????, ?????????????????????????????????????????????????????????. ????????????????????????????????????????????????????????????????????????????????????. 1???????????????????????????????????????, 1-??????????????????-1-(3-?????????????????????) ?????????-2-?????????????????????3-????????????????????????????????????????????????????????????????????????. ???????????????????????????????????????????????????????????????????????????????????????????????????, 1-??????????????????-1-[N-?????????(?????????)-N-(3-?????????????????????)] ?????????-2-?????????????????? (9b-1,2) ????????????????????????, ????????????????????????????????????, ???????????????????????????????????????????????????????????????.
Compounds in which two methyl groups of acetamiprid are replaced with a set of substituents were prepared and the presence of the two retainers was confirmed from NMR spectra. The insecticidal activities against American cockroaches and houseflies were measured by injection methods with or without metabolic inhibitors. The modified compounds were weaker than acetamiprid in their insecticidal activities against both species. A metabolic inhibitor, piperonyl butoxide, increased the insecticidal activities and in combination with NIA 16388 enlarged the rates of increase. The neuroblocking activity of the compounds was measured with excised central nerve cord of the cockroach. Here also the substitution with bulky groups at the terminal site or on the amino nitrogen atom lowered the neuroactivity, the lowering rate being greater in the former. The insecticidal potency for the cockroach with both metabolic inhibitors correlated well with the neuroblocking activity when the hydrophobicity factor of compounds was calculated separately.
pesticides can be considered a milestone in insecticide
research of the past three decades. Neonicotinoids
represent the fastest-growing class of
insecticides introduced to the market since the
commercialization of pyrethroids (Nauen and
Bretschneider, 2002). Like the naturally occurring
nicotine, all neonicotinoids act on the insect central
nervous system (CNS) as agonists of the postsynaptic
nicotinic acetylcholine receptors (nAChRs) (Bai
et al., 1991; Liu and Casida, 1993a; Yamamoto,
1996; Chao et al., 1997; Zhang et al., 2000;
Nauen et al., 2001), but, with remarkable selectivity
and efficacy against pest insects while being safe for
mammals.The discovery of neonicotinoids as important novel pesticides can be considered a milestone in insec-ticide research of the past three decades. Neo-nicotinoids represent the fastest-growing class of insecticides introduced to the market since the commercialization of pyrethroids (Nauen and Bretschneider, 2002). Like the naturally occurring nicotine, all neonicotinoids act on the insect central nervous system (CNS) as agonists of the postsynap-tic nicotinic acetylcholine receptors (nAChRs) (Bai et al., 1991; Liu and Casida, 1993a; Yamamoto, 1996; Chao et al., 1997; Zhang et al., 2000; Nauen et al., 2001), but, with remarkable selectivity and efficacy against pest insects while being safe for mammals. As a result of this mode of action there is no cross-resistance to conventional insecticide clas-ses, and therefore the neonicotinoids have begun replacing pyrethroids, chlorinated hydrocarbons, organophosphates, carbamates, and several other classes of compounds as insecticides to control in-sect pests on major crops (Denholm et al., 2002). Today the class of neonicotinoids are part of a single mode of action group as defined by the Insecticide Resistance Action Committee (IRAC; an Expert Committee of Crop Life) for pest management purposes (Nauen et al., 2001). Neonicotinoids are potent broad-spectrum in-secticides possessing contact, stomach, and systemic activity. They are especially active on hemipteran pest species, such as aphids, whiteflies, and planthop-pers, but they are also commercialized to control coleopteran and lepidopteran pest species (Elbert et al., 1991, 1998). Because of their physicochemi-cal properties they are useful for a wide range of different application techniques, including foliar, seed treatment, soil drench, and stem application in
Effective management of pest insect populations in most of the world' s agriculture and horticulture is dependent on a variety of inputs including a ready supply of safe, highly efficacious chemical insecticides. Likewise, effective control of insect pests of animal health and public health is also highly dependent on the availability of insecticidal products. With their abundant numbers and short life-cycles, populations of pest insects can readily develop resistance to the insecticides used against them with the result that once effective insecticides are no longer able to control the pests for which they were intended. Accordingly, resistance may be usefully defined as 'a heritable change in the sensitivity of a pest population that is reflected in the repeated failure of a product to achieve the expected level of control when used according to the label recommendation for that pest species'. This definition differs slightly from others in the literature, however we believe it represents the most accurate, practical definition of relevance to farmers and growers. The agrochemical industry views resistance as an extremely serious threat and an issue that needs a proactive approach. Effective insecticide resistance management (IRM) is essential and the industry-wide Insecticide Resistance Action Committee (IRAC) is dedicated to making this a reality.
IntroductionObjectives of the IRACStructure and Organization of the IRACActivitiesPrinciples of ResistanceThe Mode of Action (MoA) Classification Scheme v7.0, August 2010Effective IRM Strategies and Approved PrinciplesFuture Market TrendsConclusions
References
Thiamethoxam is the first commercial neonicotinoid insecticide from the thianicotinyl subclass. It was discovered in the course of our optimisation program on neonicotinoids started in 1985. Novel variations of the nitroimino-heterocycle of imidacloprid led to 4-nitroimino-1,3,5-oxadiazinanes exhibiting high insecticidal activity. Among these, thiamethoxam (CGA 293433) was identified as the best compound and selected for worldwide development. The compound can be synthesised in only a few steps and high yield from easily accessible starting materials. Thiamethoxam acts by binding to nicotinic acetylcholine receptors. It exhibits exceptional systemic characteristics and provides excellent control of a broad range of commercially important pests, such as aphids, jassids, whiteflies, thrips, rice hoppers, Colorado potato beetle, flea beetles and wireworms, as well as some lepidopteran species. In addition, a strong preventative effect on some virus transmissions has been demonstrated. Thiamethoxam is developed both for foliar/soil applications and as a seed treatment for use in most agricultural crops all over the world. Low use rates, flexible application methods, excellent efficacy, long-lasting residual activity and favourable safety profile make this new insecticide well-suited for modern integrated pest management programmes in many cropping systems.© 2001 Society of Chemical Industry
The tobacco whitefly, Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) which occurs in various parts of the world, has developed a high degree of resistance against several chemical classes of insecticide, including organophosphates, carbamates, pyrethroids, insect growth regulators and chlorinated hydrocarbons. The present studies were done in order to monitor the susceptibility of whitefly populations in southern Spain to insecticides commonly used there. Systemic bioassays using Spanish field populations of B tabaci collected in 1994, 1996 and 1998 indicated an increase, albeit a slow one, in resistance to imidacloprid over this period. Comparative studies of other neonicotinoids using the same bioassay revealed a high degree of cross-resistance to acetamiprid and thiamethoxam. Leaf-dip bioassays with adult females from these populations revealed a high level of resistance to cyfluthrin, endosulfan, monocrotophos, methamidophos, and pymetrozine, each at 200 mg litre−1. Buprofezin and pyriproxyfen were tested against second-instar nymphs and eggs, respectively. Buprofezin also showed a lower efficacy against ESP-98, a strain of B tabaci received from Almeria in 1998, but pyriproxyfen resistance was not obvious when tested against eggs of strain ESP-98. Field trials in 1998 revealed good efficacy of imidacloprid in one farm in the Almeria region and two greenhouses in Murcia and Sevilla, but a loss of activity by imidacloprid in another farm in the Almeria region. Cross-resistance between imidacloprid and thiamethoxam was also confirmed under field conditions.© 2000 Society of Chemical Industry
The effects of sublethal dosages of the chloronicotinyl insecticide imidacloprid on different strains of the tobacco whitefly, Bemisia tabaci Gennadius (Homoptera: Aleyrodidae), have been studied after leaf dip and systemic application. All bioassays were performed with the insecticide susceptible strain, SUD-S, and two Spanish biotypes, ALM-2 and LMPA-2, both resistant to conventional insecticides and with a lower susceptibility towards imidacloprid. Honeydew, excreted by all strains feeding on treated and untreated cotton leaf discs was quantified by photometric analysis of its carbohydrate content. EC50-values for the depression of honeydew excretion in female adults after systemic application of imidacloprid were calculated at 0.037ppm, 0.027ppm and 0.048ppm for strains SUD-S, ALM-2 and LMPA-2, respectively, indicating no significant differences between strains in feeding behaviour throughout an 48h testing period. Depending on the strain these EC50-values were 150- to 850-times lower than LC50-values calculated for mortality in the same bioassay. Starvation tests revealed mean survival times of >48h for female adults placed on agar without leaf discs, indicating that sublethal dosages of imidacloprid which caused antifeedant responses, were probably not covered in common 48h systemic bioassays, used to monitor resistance to imidacloprid. Effects of sublethal dosages on honeydew excretion after leaf dip application seem to be minor. In choice situations with systemically treated and untreated leaf discs in a single container, female adults of B.tabaci showed a clear preference for the untreated leaf discs. However, when using leaf discs treated by painting the surface with imidacloprid in the same bioassay, feeding activities on treated and untreated leaf discs were not significantly different. The results of the present study demonstrate the antifeedant properties of imidacloprid on B.tabaci, which might play an essential role after soil application or seed treatment under field conditions.
Thiacloprid, a new chloronicotinyl insecticide, is targeted chiefly to control aphid pest species in orchards and vegetables. In a standard IOBC glass plate assay, residues of thiacloprid (SC 480) severely affected adult stages of the cereal aphid parasitoid Aphidius rhopalosiphi whereas pre-imaginal stages (which develop within the host) remained unaffected. As for A. rhopalosiphi, the pre-imaginal stages of the crop-relevant egg parasitoid T. cacoeciae were not adversely affected by a spray treatment with thiacloprid (SC 480). However, when treated host eggs were stored under greenhouse conditions, the emergence success of ecdysed parasitoids was significantly reduced. This is assumed to be caused by thiacloprid residues that had been deposited on the host egg cuticle during spray treatment and which were ingested by the parasitoids during emergence, when they were biting its way through the host egg cuticle. In contrast, if treated host eggs were subjected to field exposure conditions before emergence of the parasitoids, no statistically significant reduction in emergence success was recorded. Moreover, the fitness of parasitoids emerging from treated host eggs was not reduced compared to untreated parasitoids. Since pre-imaginal stages comprise a major part of a parasitoid population and were not affected in a lethal or sublethal way by thiacloprid (SC 480), we conclude that a spray treatment with thiacloprid (SC 480) in the field will not significantly interfere with the pest control function of a parasitoid fauna in the target crops.
Neonicotinoids represent a novel and distinct chemical class of insecticides with remarkable chemical and biological properties. In 1985, a research programme was started in this field, in which novel nitroimino heterocycles were designed, prepared and assayed for insecticidal activity. The methodology for the synthesis of 2-nitroimino-hexahydro-1,3,5-triazines, 4-nitroimino-1,3,5-oxadiazinanes and 4-nitroimino-1,3,5-thiadiazinanes is outlined. Bioassays demonstrated that 3-(6-chloropyridin-3-ylmethyl)-4-nitroimino-1,3,5-oxadiazinane exhibited better insecticidal activity than the corresponding 2-nitroimino-hexahydro-1,3,5-triazine and 4-nitroimino-1,3,5-thiadiazinane. In most tests, this compound was equally or only slightly less active than imidacloprid. A series of structural modifications on this lead structure revealed that replacement of the 6-chloro-3-pyridyl group by a 2-chloro-5-thiazolyl moiety resulted in a strong increase of activity against chewing insects, whereas the introduction of a methyl group as pharmacophore substituent increased activity against sucking pests. The combination of these two favourable modifications led to thiamethoxam (CGA 293 343). Thiamethoxam is the first commercially available second-generation neonicotinoid and belongs to the thianicotinyl sub-class. It is marketed under the trademarks Actara for foliar and soil treatment and Cruiser for seed treatment. The compound has broad-spectrum insecticidal activity and offers excellent control of a wide variety of commercially important pests in many crops. Low use rates, flexible application methods, excellent efficacy and the favourable safety profile make this new insecticide well-suited for modern integrated pest management programmes in many cropping systems.
It had been found earlier that the chloronicotinyl insecticide thiacloprid (as the 480 g litre(-1) SC Calypso) poses a favourably low toxicity hazard to the honeybee, Apis mellifera L. As with pyrethroids, the metabolization of chloronicotinyl compounds involves monooxygenases, which are known to be inhibited by some ergosterol biosynthesis inhibitor (EBI) fungicides potentially co-applied with these insecticides. The potential synergistic enhancement of the toxicity of thiacloprid to honeybees when co-applied with such fungicides was therefore studied under laboratory and semi-field conditions. Fungicides of other chemical classes were also examined for synergistic potential to reveal other metabolic interactions. In the laboratory, only a slight synergistic effect was observed with the anilinopyrimidine fungicide examined, while a significant enhancement of thiacloprid toxicity to honeybees was found with EBI fungicides. In three tunnel tests conducted under different environmental conditions to simulate field exposure, no increased mortality was observed when honeybees were directly sprayed with thiacloprid (Calypso) alone or in combination with the EBI fungicide tebuconazole (250 g litre(-1) EW, Folicur). There was also no synergized reduction in the foraging intensity on the treated crop. In general, the foraging intensity decreased after thiacloprid treatment but was restored within 24-48 h. The hive vitality was not affected by either thiacloprid or its tank mix with tebuconazole. Our results suggest that, at the recommended use rates, thiacloprid poses a negligible lethal risk to honeybees when applied either alone or in tank mixes with fungicides of various chemical classes.
The susceptibility to several insecticides of 16 and 8 strains of Myzus persicae Sulzer and Aphis gossypii Glover, respectively, received from different European countries in 2001 was investigated. Most of the strains were derived from places known for their aphid resistance problems to conventional insecticides before imidacloprid was introduced. In many regions and agronomic cropping systems imidacloprid has been an essential part of aphid control strategies for a decade, and therefore the susceptibility of aphid populations to imidacloprid using FAO-dip tests and diagnostic concentrations in a leaf-dip bioassay was checked. Additional insecticides tested were cyfluthrin (chemical class: pyrethroid), pirimicarb (carbamate), methamidophos and oxydemeton-methyl (organophosphates). Diagnostic concentrations (LC99-values of reference strains) for each insecticide were established by dose response analysis using a new leaf-disc dip bioassay format in 6-well tissue culture plates. Virtually no resistance to imidacloprid in any of the field-derived populations of M. persicae and A. gossypii was detected. In contrast, strong resistance was found to pirimicarb and oxydemeton-methyl, and to a lesser extent also to cyfluthrin. Two strains of A. gossypii exhibited reduced susceptibility to imidacloprid when tested directly after collection. However, after maintaining them for six weeks in the laboratory, the aphids were as susceptible as the reference strain. The diagnostic concentration of methamidophos did not reveal any resistance in M. persicae, but did so in four strains of A. gossypii.
The first neonicotinoid insecticide introduced to the market was imidacloprid in 1991 followed by several others belonging to the same chemical class and with the same mode of action. The development of neonicotinoid insecticides has provided growers with invaluable new tools for managing some of the world's most destructive crop pests, primarily those of the order Hemiptera (aphids, whiteflies, and planthoppers) and Coleoptera (beetles), including species with a long history of resistance to earlier-used products. To date, neonicotinoids have proved relatively resilient to the development of resistance, especially when considering aphids such as Myzus persicae and Phorodon humuli. Although the susceptibility of M. persicae may vary up to 20-fold between populations, this does not appear to compromise the field performance of neonicotinoids. Stronger resistance has been confirmed in some populations of the whitefly, Bemisia tabaci, and the Colorado potato beetle, Leptinotarsa decemlineata. Resistance in B- and Q-type B. tabaci appears to be linked to enhanced oxidative detoxification of neonicotinoids due to overexpression of monooxygenases. No evidence for target-site resistance has been found in whiteflies, whereas the possibility of target-site resistance in L. decemlineata is being investigated further. Strategies to combat neonicotinoid resistance must take account of the cross-resistance characteristics of these mechanisms, the ecology of target pests on different host plants, and the implications of increasing diversification of the neonicotinoid market due to a continuing introduction of new molecules.
Susceptibilities of UK and mainland European samples of Trialeurodes vaporariorum (Westwood) to the neonicotinoid insecticide imidacloprid were investigated over a 7 year period. All 24 strains collected between 1997 and 2003 showed similar baseline levels of susceptibility to that of a known susceptible laboratory strain when exposed to a diagnostic concentration (128 mg L(-1)) of formulated imidacloprid. Two samples collected during 2004, one from the UK and one from The Netherlands, demonstrated reduced susceptibility at this concentration. Using dose-response assays, the presence of resistant individuals was disclosed in both these strains; some individuals were unaffected at doses high enough to induce phytotoxic effects. This report represents the first confirmed cases of neonicotinoid resistance inducing control failures in T. vaporariorum, and highlights a need for careful vigilance to sustain the effectiveness of imidacloprid and related neonicotinoid insecticides.
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