New Class Of Insecticides Research Articles

Acute Poisoning with Neonicotinoid Insecticides: A Case Report and Literature Review

Neonicotinoids are a new class of insecticides widely applied for crop protection. These insecticides act as agonists at nicotinic acetylcholine receptors, which cause insect paralysis and death. The high specificity for receptors in insects was considered to possess highly selective toxicity to insects and relative sparing of mammals. However, an increasing number of cases of acute neonicotinoid poisoning have been reported in recent years. We reported a man who developed respiratory failure and shock after ingestion of neonicotinoid insecticide. A detailed literature review found that respiratory, cardiovascular and certain neurological presentations are warning signs of severe neonicotinoid intoxication. The amounts of ingested neonicotinoid insecticide and the plasma neonicotinoid concentration are not useful guides for the management of intoxicated patients. Supportive treatment and decontamination are the practical methods for the management of all neonicotinoid-poisoned patients.

Resistance to diamide insecticides in diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae) is associated with a mutation in the membrane-spanning domain of the ryanodine receptor

Diamide insecticides such as chlorantraniliprole and flubendiamide are a new class of insecticide that selectively target insect ryanodine receptors (RyR), a distinct class of homo-tetrameric calcium release channels which play a pivotal role in calcium homeostasis in numerous cell types. Resistance to these insecticides has recently been reported in the diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae), a global lepidopteran pest of cruciferous crops. In the present study a region of the gene encoding the proposed diamide binding site of the RyR from P. xylostella collected from the Philippines and Thailand and found to be over 200-fold resistant to both chlorantraniliprole and flubendiamide compared to susceptible strains, were amplified by RT-PCR and sequenced. Comparison of the sequence with those from several susceptible reference strains revealed non-synonymous mutations in each of the resistant strains that in both cases lead to a glycine to glutamic acid substitution (G4946E) in the protein. The independent evolution of the same amino acid substitution within a highly conserved region of the proposed diamide binding site in two geographically separated resistant strains of P. xylostella strongly suggests a causal association with diamide resistance. Furthermore we designed a pyrosequencing-based diagnostic assay for resistance monitoring purposes that can be used to detect the G4946E mutation in field-collected samples of diamondback moth. The implications of the reported findings for resistance management strategies are discussed.

Short-term effects of a spinosyn's family insecticide on energy metabolism and liver morphology in frugivorous bats Artibeus lituratus (Olfers, 1818)

A new class of insecticide derived from fermentation of Sacharopolyspora spinosa - spinosad, has been indicated as being of low toxicity and a natural alternative to classical pesticides. In order to elucidate several aspects related to the morphophysiological changes induced by spinosad in Artibeus lituratus, the effects of a seven-day administration on plasma glucose, glycogen, protein and lipid concentrations were evaluated, and possible changes in liver cells were examined by histological analysis. Animals were fed with spinosyn-contaminated fruit through immersion in a solution. Data reporting on metabolism revealed a decrease in hind limb muscle lipid concentration in the treated group. Morphological analysis indicated a significant increase in liver cell diameter in treated animals compared to the control group. This study indicates that spinosyn, used at its recommended dose, does not affect general energy metabolism in A. lituratus but may affect some ultrastructural characteristics of liver cells.

BIO-EFFICACY OF RYNAXYPYR 20% SC (CHLORANTRANILIPROLE), A NEW MOLECULE, AGAINST EGGPLANT SHOOT AND FRUIT BORER

Field investigations were undertaken for two consecutive crop seasons to study the bio-efficacy of rynaxypyr 20% SC (Chlorantraniliprole), the only representative of a new class of insecticide, anthranilic diamide against eggplant shoot and fruit borer at Bidhan Chandra Krishni Viswavidyalaya, West Bengal, India. Cypermethrin 10% EC at 60 g a.i./ha and cartap hydrochloride 50% SP at 350 g a.i./ha were used as standard checks. Rynaxypyr 20% SC at 20-60 g a.i./ha significantly reduced shoot and fruit infestation by the pest compared with the untreated control and cartap hydrochloride 50% SP at 350 g a.i./ha, and increased the yield significantly. However, 40-60 g a.i./ha dosages of the insecticide showed better performance and gave significantly higher yields than the lower dosages, and to some extent with cypermethrin 10% EC at 60 g a.i./ha. Cartap hydrochloride 50% SP at 350 g a.i./ha showed higher percentages of fruit damage than the control. Considering the bio-efficacy of the insecticide and yield of egg plant, rynaxypyr 20% SC at 40 g a.i./ha is suggested for effective management of egg plant shoot and fruit borer. Rynaxypyr 20% SC at different dosages did not cause any significant reduction in the predatory fauna present on the eggplant ecosystem. This insecticide, even at a dosage of 300 g a.i./ha, did not produce any phytotoxicity to the treated eggplant crop.

Evaluation of mutagenic potential of acetamiprid by dominant lethal test on Culex quinquefasciatus

Acetamiprid, a member of the neonicotinoid insecticide family, is a new class of insecticide which has recently entered the market place. It is very selective and provides outstanding control of sucking pests such as aphids and whiteflies of major crops. In the present investigation, dominant lethal test (DLT) is adopted for the evaluation of the genotoxic effects of acetamiprid using Culex quinquefasciatus as an experimental model. In this experiment, the males hatched from larvae treated with LD40 were cross mated with normal females and the results were based on the number of hatched and unhatched eggs laid by these females. The statistical analysis of the results for LD40 treated groups gave the values of 37.526±3.886 as against 5.23±0.77 from the nontreated groups which indicated significant dominant lethality of p<0.01. These results indicated that exposure of pesticides even at small dose level proved deleterious to the genome of mosquito and its subsequent generation.

Interaction of Imidacloprid with Hemoglobin by Fluorescence and Circular Dichroism

Imidacloprid belongs to a major new class of insecticides, called neonicotinoids, which are accounting for 11-15% of the total insecticide market. The binding characteristics of insecticide imidacloprid with hemoglobin (Hb) have been studied by employing different spectroscopic techniques. The results proved the formation of complex between imidacloprid and Hb. Hydrophobic interaction and hydrogen bond dominated in the association reaction. Hydrophobic probe 8-anilino-1-naphthalenesulfonic acid (ANS) competitive experiments indicated that the binding of imidacloprid to Hb primarily took place in hydrophobic regions. The distance between Hb donor and acceptor imidacloprid was 4.88 nm as derived from Förster's theory. Alternations of Hb secondary structure in the presence of imidacloprid were confirmed by synchronous fluorescence, circular dichroism (CD) and three-dimensional fluorescence spectra. This study enriches our understanding of toxic effect of imidacloprid to the physiologically important protein Hb.

Mechanism of action of sodium channel blocker insecticides (SCBIs) on insect sodium channels

Sodium channel blocker insecticides (SCBIs) are a relatively new class of insecticides, with a mechanism of action different from those of other classes of insecticides that target voltage-gated sodium channels. These compounds have no effect at hyperpolarized membrane potentials, but cause a voltage-dependent, nearly irreversible block as the membrane potential is depolarized. The mechanism of action of SCBIs is similar to that of local anesthetics (LAs), class I anticonvulsants and class I antiarrhythmics. In this article, we review the physiological actions of these compounds on the whole animal, the nervous system and sodium channels, and also present the results from recent studies that elucidate the receptor site of SCBIs.

Strain construction for enhanced production of spinosad via intergeneric protoplast fusion

Spinosad is a new class of insecticides produced by Saccharopolyspora spinosa. The aim of this study was to construct a starch-utilizing strain that overproduced spinosad by intergeneric fusion between S. spinosa and Streptomyces avermitilis. Protoplast fusion is an important technique for engineering microbial strains, especially for microorganisms with few available molecular genetic tools. Protoplast fusion was conducted with UV-irradiated protoplasts of S. spinosa and S. avermitilis. Among 76 recombinants screened by ESI-MS and HPLC, a starch-utilizing strain F17, identified as S. spinosa, was obtained. The yield of spinosad in F17 was increased by 447.22%, compared with the yield of the wild-type strain. This is the first report of intergeneric protoplast fusion between S. spinosa and S. avermilitis, which shows great potential for industrial applications.

Role of the sixth transmembrane segment of domain IV of the cockroach sodium channel in the action of sodium channel blocker insecticides

Sodium channel blocker insecticides (SCBIs), such as indoxacarb and metaflumizone, are a new class of insecticides with a mechanism of action different from those of other insecticides that target sodium channels. SCBIs block sodium channels in a manner similar to local anesthetics (LAs) such as lidocaine. Several residues, particularly F1579 and Y1586, in the sixth transmembrane segment (S6) of domain IV (IV) of rat Na v1.4 sodium channels are required for the action of LAs and SCBIs and may form part of overlapping receptor sites. However, the binding site for SCBIs in insect sodium channels remains undefined. We used site-directed mutagenesis, the Xenopus laevis oocyte expression system, and the two-electrode voltage clamp technique to study the effects on SCBI activity of mutating F1817 and Y1824 (analogous to those residues identified in mammalian sodium channels) to alanine, in the voltage-sensitive sodium channel of the German cockroach, Blattella germanica. The mutant channels showed no effect or a marked increase in channel sensitivity to both DCJW (the active metabolite of indoxacarb) and metaflumizone. Thus, it appeared that although the F1817 residue plays a role in the action of SCBIs and that both residues are involved in LA activity in mammalian sodium channels, neither F1817 nor Y1824 are integral determinants of SCBI binding on insect sodium channels. Our results suggest that the receptor site of SCBIs on insect sodium channels may be significantly different from that on mammalian sodium channels.

Neonicotinoid insecticides: an emerging cause of acute pesticide poisoning

Introduction. Neonicotinoids are a relatively new class of insecticides. They exhibit agonistic effects at postsynaptic nicotinic receptors in insects and are believed to have low toxicity in humans. Methods. We conducted a retrospective analysis of all neonicotinoid exposures reported to the Taiwan National Poison Center to better understand the toxicity profile of neonicotinoid insecticides. Results. A total of 70 patients were analyzed. Most exposures involved suicidal ingestions of imidacloprid alone. Clinical manifestations of neonicotinoid insecticide toxicity bear some resemblance to those of acute nicotine poisoning. Although most exposures were of mild-to-moderate severity, eight patients developed major effects and two died. Aspiration pneumonia and respiratory failure were the main cause of severe toxicity. Conclusion. Significant toxicity of neonicotinoids can occur following large amount of oral ingestion. Poisoned patients may present with cholinergic syndrome, and judicious use of atropine seems justified. Symptomatic treatment, especially ventilator support, remains most important in clinical management.

Separation and identification of botanical insecticide 7-hydroxycoumarin and its biological activity against Aphis craccivora and Culex pipiens pallens

The root powder of Stellera chamaejasme was extracted with chloroform. The crude extract obtained was chromatographed with silica gel columns many times. One pure natural product was obtained. It was identified as 7-hydroxycoumarin. Laboratory bioassay showed that it had a good insecticidal activity against Aphis craccivora and Culex pipiens pallens. Its median lethal concentrations (LC50) (24 h after treatment) were 19.56 and 0.435 mg L−1, respectively. The results of regressive and correlative analysis demonstrated that the correlations were very significant between concentration and efficacy. The corresponding correlative coefficients were 0.9686 and 0.9712, respectively. This is the first report of the insecticidal activity of 7-hydroxycoumarin. It may represent a new class of insecticides.

Efficacy of Eight Larvicidal Botanical Extracts from Khaya senegalensis and Daucus carota against Culex annulirostris

The failure to discover a significant new class of insecticides has led many researchers back to biodiscovery studies in the search for new and economically viable alternatives. After a preliminary screening of botanical extracts using descending series of concentrations (1,000, 500, 100, 50, and 5 mg/liter), 8 extracts from 2 potential botanical agents, Khaya senegalensis (Desrousseaux) and Daucus carota L., were tested against 4th instars of Culex annulirostris (Skuse) following the standard World Health Organization insecticide susceptibility methodology. The median lethal concentration (LC50) values for K. senegalensis against Cx. annulirostris using acetone, ethanol, hexane, and methanol extracts were 20.12, 5.1, 5.08, and 7.62 mg/liter, respectively. The LC50 values for D. carota against Cx. annulirostris using acetone, ethanol, hexane, and methanol extracts were 236.00, 36.59, 77.19, and 241.8 mg/liter, respectively. Extracts from K. senegalensis were more potent than those from D. carota against Cx. annulirostris and hexane and ethanol were the best solvents to extract essential oils from both plant species, respectively. In potency, K. senegalensis was similar to azadirachtin, but fractionation and compound isolation of the hexane extract in particular may reveal a potent phytochemical that could be compared to synthetic mosquitocides.

Anthranilic diamides: A new class of insecticides with a novel mode of action, ryanodine receptor activation

Development of insecticides with unique modes of action is necessary to combat widespread insecticide resistance. A new class of insecticides has been discovered, the anthranilic diamides, that provides exceptional control through action on a novel target, the ryanodine receptor. Anthranilic diamides potently activate this receptor, releasing stored calcium from the sarcoendoplasmic reticulum causing impaired regulation of muscle contraction. Expression of a recombinant Drosophila ryanodine receptor in a lepidopteran cell line confers sensitivity to anthranilic diamides similar to that observed with native receptors. Ligand-binding studies with radiolabeled ryanodine and radiolabeled anthranilic diamide in Periplaneta americana reveal a single, saturable binding site for this chemistry distinct from that of ryanodine. Further, calcium mobilization studies using mammalian cell lines indicate anthranilic diamides exhibit >500-fold differential selectivity toward insect, over mammalian, receptors. Consequently, anthranilic diamides offer a novel pharmacological tool for calcium signaling research in addition to a unique alternative to existing pest-management strategies.

Acute ®Confidor (imidacloprid-N-methyl pyrrolidone) insecticides intoxication with mimicking cholinergic syndrome

Confidor, consisting of two major components - imidacloprid and the solvent N-methyl pyrrolidone is a relatively new class of insecticide. Reports of acute overdose or adverse effects after human exposure have been few, despite wide usage. We report a case of acute confidor intoxication with mimicking cholinergic syndrome, the patient ultimately dying of nosocominal pneumonia. Patients ingesting large volumes of imidacloprid-N-methyl pyrrolidone insecticide formulations require close observation and supportive treatment.

Managing resistance is critical to future use of pyrethroids and neonicotinoids

Synthetic pyrethroids and neonicotinoids are the most readily available alternatives to the organophosphate and carbamate insecticides. Pyrethroids have become widely used in California, and problems with insecticide resistance and nontarget impacts have already been identified. Neonicotinoids are a new class of insecticide with uses only now being realized. Managing insecticide resistance will be crucial to preserving these new materials as organophosphate uses are lost.

Neonicotinoids and Derivatives: Effects in Mammalian Cells and Mice

Neonicotinoids are the only major new class of insecticides introduced in the past three decades. They act as selective agonists at the insect nicotinic acetylcholine receptor and are therefore highly toxic towards important insect pests but relatively safe to mammals. However, the excellent selective toxicity may not be evident with their metabolites or analogous compounds. The aim of this paper is to consider the effects of neonicotinoids and derivatives in mammalian cells and mice involving up-regulation of nicotinic receptor levels and activation of the intracellular signal integration cascade elicited by chronic or sustained exposure and analgesic and toxic effects in mice.

The discovery of pyridalyl: a novel insecticidal agent for controlling lepidopterous pests.

Synthesis of analogues of two compounds with known insecticidal activity, both of which contain a 3,3-dichloro-2-propenyloxy group, produced 2-(trifluoromethyl)-4-phenoxyphenyl 3,3-dichloro-2-propenyl ether, which had weak activity against lepidopterous larvae. Structural modifications around this lead compound led to the development of pyridalyl [Pleo, S-1812; 2,6-dichloro-4-(3,3-dichloroallyloxy)phenyl 3-[5-(trifluoromethyl)-2-pyridyloxy]propyl ether], which belongs to a new class of insecticides. Pyridalyl gives very good control of various lepidopterous and thysanopterous pests on cotton and vegetables, without phytotoxicity. It controls populations of Heliothis virescens F and Plutella xylostella (L) which are resistant to various currently used insecticides. It also produces unique insecticidal symptoms, so it may have a different mode of action from other existing insecticides. Pyridalyl is also less harmful than existing insecticides to various beneficial arthropods, so it should provide an important tool in IPM and insecticidal management programmes for the control of lepidopterous and thysanopterous pests. The first market introduction is expected in Japan and some Asian countries in the years between 2004 and 2005.

Evaluation of spinosad in a two-generation dietary reproduction study using Sprague-Dawley rats.

Spinosad, an insecticide derived from a naturally occurring bacterium via fermentation, represents a new class of insecticides acting by a novel mode of action. A dietary study was conducted in Sprague-Dawley rats in which groups of 30 rats/sex/dosage level were given diets that provided 0, 3, 10, or 100 mg spinosad/kg body weight/day, 7 days/week, for 2 successive generations. Following 10 weeks of dietary exposure, the P1 generation was mated twice to produce F1a and F1b litters. After weaning, groups of 30 rats/sex/dosage level were selected from the F1a litters, given diets containing spinosad for 12 weeks, and mated to produce the F2 generation. Dietary administration of spinosad to rats at a dosage of 100 mg/kg/day over 2 generations produced parental toxicity and effects on the offspring. Among adult males, body weights and weight gains were decreased 2-9% relative to controls, with P1 males more affected than P2. Absolute and relative liver, kidney, heart, spleen, and thyroid weights were increased by from 12% to as much as 240% of control values. Histologic changes consistent with cationic amphiphilic compounds were noted in the kidneys, lungs, mesenteric lymph nodes, spleen, and thyroid of P1 and P2 males and females. In females given 100 mg/kg/day, though premating body weights were not affected, weight gains during the F1a and F1b gestation periods were depressed 15-16%. Increased incidences of dystocia, and vaginal bleeding and mortality occurred during parturition and lactation at 100 mg/kg/day. Effects on the offspring (decreased litter size and survival through day 4 of lactation) were limited to the high-dosage group. Signs indicative of poor maternal care noted in the pups (stomachs void of milk, cold, thin, etc.) were observed at 100 mg/kg/day. Early postnatal effects on the offspring were considered likely secondary to the effects in maternal animals around the time of parturition. At 100 mg/kg/day, weight gain in pups was depressed throughout lactation, with statistically significantly decreased weights noted toward the latter half of the lactation period. There were no treatment-related effects on adults or their offspring at 3 or 10 mg/kg/day in either generation. Based on these results, spinosad is not considered a selective reproductive toxicant, (i.e., no effects on reproductive parameters were noted below a level that produced toxicity in the adults) and the no observed effect level (NOEL) for both parental and reproductive/perinatal toxicity was 10 mg/kg/day.

Control of the Whitefly Trialeurodes vaporariorum Westw. (Homoptera, Aleyrodidae) on tomato by the new insecticide Acetamiprid

The efficacy of a new class of insecticide (chloronicotinyl) Mospilan 20 SP (a. i. acetamiprid), compared with Lannate 90 SL (a. i. methomyl) and Applaud WP 25 (a. i. buprofezin), in glasshouse control of whitefly (Trialeurodes vaporariorum) on tomatoes, was investigated. All investigated insecticides significantly decreased the number of whitefly larvae, compared with untreated plots where population density grew during the trial. Based on statistical analysis, efficacy of all insecticides on whitefly larvae were in the same category. Some differences occurred 7 days after the third treatment. Deposited egg number was significantly different between checks and each insecticide plot. Efficacy of investigated insecticides, evaluated according to deposited egg number, was also good and in the same category.

Indoxacarb, an oxadiazine insecticide, blocks insect neuronal sodium channels.

1. Decarbomethoxyllated JW062 (DCJW), the active component of a new oxadiazine insecticide DPX-JW062 (Indoxacarb), was tested on action potentials and the inward sodium current recorded from short-term cultured dorsal unpaired median neurones of the cockroach Periplaneta americana. 2. Under whole-cell current-clamp conditions, 100 nM DCJW reduced the amplitude of action potentials and induced a large hyperpolarization of the resting membrane potential associated with a 41% increase in input resistance. 3. In voltage-clamp, DCJW resulted in a dose-dependent inhibition (IC(50) 28 nM) of the peak sodium current. Based on IC(50) values, the effect of DCJW was about 10 fold less potent than tetrodotoxin (TTX) but 1000 fold more potent than the local anaesthetic lidocaine. DCJW (100 nM) was without effect on activation properties of the sodium current, reversal potential, voltage dependence of sodium conductance and on both fast and slow steady-state inactivations. 4. TTX (2 nM) resulted in 48% inhibition of the peak inward sodium current. Co-application of TTX (2 nM) with various concentrations of DCJW produced an additional inhibition of the peak inward current, indicating that the blocking actions of DCJW and TTX were distinct. Co-application of lidocaine (IC(50) 30 microM) with various concentrations of DCJW produced a reduction of the apparent potency of DCJW, suggesting that DCJW and lidocaine acted at the same site. 5. DCJW (100 nM) did not affect inward calcium or outward potassium currents. 6. This study describes, for the first time, the action on insect neuronal voltage-dependent sodium channels of Indoxacarb, a new class of insecticides.