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PubMed1991

Inter and intraindividual variations in plasma cholinesterase activity and substance concentration in employees of an organophosphorus insecticide factory.

During a period of 10 months, inter and intraindividual variations in plasma cholinesterase (ChE) activity were studied in 331 employees of an organophosphorus insecticide factory, and in 193 healthy volunteers without occupational exposure to known ChE inhibitors. Repeated (n = 6) measurements of ChE activity and ChE substance concentration were performed in 410 subjects. The study showed substantial intraindividual variations of ChE activity and ChE substance concentration (up to 40%) in the employees and in the reference group. When effects due to sex, ChE-1 phenotype, body weight, and height were considered, one subgroup of employees of the organophosphorus insecticide factory showed a significantly lower average ChE activity than other subgroups; as ChE substance concentrations were found to be proportionally decreased, it was concluded that the low ChE activity was unrelated to occupational exposure. A combined determination of ChE activity and ChE substance concentration is recommended as a rational diagnostic tool when an unexpected decrease of plasma ChE activity is registered in people joining organophosphorus insecticide health surveillance programmes.

Adult↗
PubMed2004

Long-term, large-scale biomonitoring of the unknown: assessing the effects of insecticides to control river blindness (onchocerciasis) in West Africa.

The control of river blindness (onchocerciasis), a human disease transmitted by black flies, has been an economic and public health success in West Africa. It involved insecticide applications to as many as 50,000 km of rivers, almost weekly, in 11 countries between 1974 and 2002. The long-term biomonitoring of the effects of insecticide use on the nontarget invertebrate (primarily insect) and fish communities was initially designed on the basis of limited knowledge available for West African rivers and on information from other areas. Routine monitoring surveys demonstrated little effect on fish but produced inconclusive results for invertebrates. Research conducted beyond these surveys and current views in river and general ecology indicate that permanent damage to invertebrates from insecticiding was unlikely. The scientific progress made during the 29 years of this biomonitoring program is relevant to future, large-scale, long-term programs worldwide.

Africa, Western↗
PubMed2006

Botanical insecticides, deterrents, and repellents in modern agriculture and an increasingly regulated world.

Botanical insecticides have long been touted as attractive alternatives to synthetic chemical insecticides for pest management because botanicals reputedly pose little threat to the environment or to human health. The body of scientific literature documenting bioactivity of plant derivatives to arthropod pests continues to expand, yet only a handful of botanicals are currently used in agriculture in the industrialized world, and there are few prospects for commercial development of new botanical products. Pyrethrum and neem are well established commercially, pesticides based on plant essential oils have recently entered the marketplace, and the use of rotenone appears to be waning. A number of plant substances have been considered for use as insect antifeedants or repellents, but apart from some natural mosquito repellents, little commercial success has ensued for plant substances that modify arthropod behavior. Several factors appear to limit the success of botanicals, most notably regulatory barriers and the availability of competing products (newer synthetics, fermentation products, microbials) that are cost-effective and relatively safe compared with their predecessors. In the context of agricultural pest management, botanical insecticides are best suited for use in organic food production in industrialized countries but can play a much greater role in the production and postharvest protection of food in developing countries.

Acetogenins↗
PubMed1988

Dystonic reaction possibly induced by cholinesterase inhibitor insecticides.

A 39-year-old male presented to the emergency room following parenteral injection of a household insecticide. The patient suffered from delayed, local complications as well as a dystonic-like reaction involving the neck musculature that was relieved by intramuscular diphenhydramine. Exposure to cholinesterase inhibitor insecticides has been associated with a number of serious toxicities due to accumulation of acetylcholine at various sites. It has been suggested that dystonic reactions are caused by an imbalance between cholinergic and dopaminergic pathways in the central nervous system. Therefore, a possible explanation of the dystonic reaction in this case is the increased cholinergic activity relative to dopaminergic activity induced by the insecticide.

Adult↗
PubMedDate not supplied

Adverse impact of insecticides on the health of Palestinian farm workers in the Gaza Strip: a hematologic biomarker study.

To evaluate the health impact of insecticides on Palestinian farm workers in the Gaza Strip, the study assessed biomarkers in farm workers who used organophosphorus insecticides. Serum cholinesterase and complete blood count were determined before and after spraying of organophosphorus insecticides. Burning sensations in eyes/face (62.5%), itching/skin irritation (37.5%), and chest symptoms (29.2%) were reported. Serum butyrylcholinesterase (SBuChE) was significantly decreased at the end of the work day. Burning sensations in eyes/face and skin rash were significantly associated with inhibition of SBuChE activity (p < 0.05). Younger workers were more affected. Leukocyte and platelet counts were increased and hemoglobin decreased significantly, reflecting acute poisoning. Monitoring of SBuChE and hematologic parameters of farm workers could be useful to predict and prevent health hazards of pesticides.

Adult↗
PubMed2002

Plant growth regulatory effect and insecticidal activity of the extracts of the Tree of Heaven (Ailanthus altissima L.).

BACKGROUND: There is an urgent need to explore and utilize naturally occurring products for combating harmful agricultural and public health pests. Secondary metabolites in the leaves of the Tree of Heaven, Ailanthus altissima L. have been reported to be herbicidal and insecticidal. The mode of action, however, of the active compounds in A. altissima are not understood. In this paper, we report the chemical characteristics of the herbicidal and insecticidal components in this tree, and will discuss the effect of light on the bioactivity of the active components. RESULTS: Extracts from the fresh leaves of A. altissima showed a strong plant germination/growth inhibitory effect in laboratory bioassays against alfalfa (Medicago sativa). The effect was dose-dependent. The growth inhibitory components were in the methylene chloride soluble fraction of the extract. The effect was greater in the light than in the dark. Other fractions had plant growth enhancing effect at lower concentrations. The extract was slightly insecticidal against yellow fever mosquito larvae (Aedes aegypti). CONCLUSIONS: The extract or its semi-purified fractions of A. altissima were strong plant growth inhibitors, therefore good candidates as potential environmentally safe and effective agricultural pest management agents. The finding that light affects the activity will be useful in the application of such natural products.

Aedes↗
PubMed2005

Prodrug-oriented molecular design of neonicotinoids: preparation of imidacloprid-related 5,5-dimethoxy-1,3-diazacyclohexane derivatives and their insecticidal activity.

Prodrug-oriented molecular design was attempted for the potent acyclic neonicotinoid insecticide, clothianidin (1-(2-chloro-5-thiazolylmethyl)-3-methyl-2-nitroguanidine). Molecules bearing a CH2COCH2 bridge linking the 1,3-NH ends of clothianidin or their acetals would possibly be hydrolyzed, regenerating the mother compounds. This strategy was used to prepare seven acetals of clothianidin-based molecules that combined 2-chloro-5-thiazolylmethyl, 6-chloro-3-pyridylmethyl or 3-tetrahydrofurfuryl with a nitroimine, cyanoimine or nitromethylene group. The key intermediate, 1,3-diamino-2,2-dimethoxypropane, was prepared from the dihydroxyacetone dimer in four steps. A selected acetal showed a characteristic nerve-impulse pattern for neonicotinoids on an excised American cockroach ganglion, although the neuroblocking activity was fairly low. Some acetals were highly insecticidal against the pea aphid at 0.8-20 ppm 7 days after a spray treatment, this being in a contrast to their far weaker activity by injection into American cockroaches. The biological results suggest that the intrinsic insecticidal activities of the acetals are weak, but would exhibit enhanced activity if hydrolyzed in an external environment.

Acetals↗
PubMedDate not supplied

Action of major insecticide groups on insect cell lines of the beet armyworm, Spodoptera exigua, compared with larvicidal toxicity.

In a first series of experiments, the biological response of a continuous cell line of the beet armyworm, Spodoptera exigua, was tested with different groups of insecticides with different modes of actions: acetylcholinesterase inhibitors, acetycholine receptor agonists, inhibitors and uncouplers of oxidative phosphorylation, site I electron transport inhibitors, gamma-aminobutyric acid receptor inhibitors, chitin synthesis inhibitors, and juvenile hormone analogues. From the concentration response curves, 50% inhibition concentration (IC(50)) values were calculated. The most active compound in vitro was pyridaben with an IC(50) value of 0.0083 ppm. In a second series of experiments, the toxicity of these insecticide groups was determined on third-instar larvae of S. exigua, and lethal concentration with 50% kill (LC(50)) values were used in the evaluation of their in vivo biological activity. Toxicity bioassays showed that lufenuron was the most toxic (LC(50) = 0.098 ppm). To explain the discrepancies in biological responses in vitro with insect cells compared with in vivo conditions with whole third-instar larvae, the significance of different detoxifying enzyme systems was tested. P(450) monooxygenases, esterases, and glutathione S-transferases were measured in third-instar larvae and cells of S. exigua. Data are discussed in terms of the usefulness of insect cell cultures as tools in the screening for novel insecticide actions.

Animals↗
PubMed2006

Cis-regulatory elements in the Accord retrotransposon result in tissue-specific expression of the Drosophila melanogaster insecticide resistance gene Cyp6g1.

Transposable elements are a major mutation source and powerful agents of adaptive change. Some transposable element insertions in genomes increase to a high frequency because of the selective advantage the mutant phenotype provides. Cyp6g1-mediated insecticide resistance in Drosophila melanogaster is due to the upregulation of the cytochrome P450 gene Cyp6g1, leading to the resistance to a variety of insecticide classes. The upregulation of Cyp6g1 is correlated with the presence of the long terminal repeat (LTR) of an Accord retrotransposon inserted 291bp upstream of the Cyp6g1 transcription start site. This resistant allele (DDT-R) is currently at a high frequency in D. melanogaster populations around the world. Here, we characterize the spatial expression of Cyp6g1 in insecticide-resistant and -susceptible strains. We show that the Accord LTR insertion is indeed the resistance-associated mutation and demonstrate that the Accord LTR carries regulatory sequences that increase the expression of Cyp6g1 in tissues important for detoxification, the midgut, Malpighian tubules, and the fat body. This study provides a significant example of how changes in tissue-specific gene expression caused by transposable-element insertions can contribute to adaptation.

Adaptation, Biological↗
PubMed2004

A survey of semen indices in insecticide sprayers.

This study aims at clarifying the semen indices of insecticide sprayers who are exposed mainly to organophosphorus and pyrethroid insecticides. Eighteen male sprayers out of 54 working for 9 companies in central Japan and 18 age-matched students or medical doctors as unexposed controls participated in detailed reproductive check-ups conducted in summer and the following winter. The sprayers were exposed to insecticides more in summer, the busiest season, than winter, the off-season (p<0.05). Erythrocyte true cholinesterase activities in the sprayers were lower than in the controls in summer (p<0.05), and decreased in significant association with the increase in exposure frequency. Testicular volumes in the sprayers tended to be smaller than in the controls (p=0.06). The serum testosterone concentration in winter in the sprayers was higher than in the controls (p<0.05), though luteinizing hormone and follicle stimulating hormone concentrations were not significantly different. The sperm counts and vitality were comparable between the groups, but detailed sperm motility analysis in summer revealed that the percentages of slow progressive and nonprogressive motile sperm were twice as high in the sprayers (p<0.05), and that of rapid progressive sperm tended to be lower (p=0.06). Such differences were not observed in winter. Differential sperm morphology counts showed that interaction of group and abstinence effects were significant in sperm with normal morphology and with head deformity only in the summer check-up. Despite possible inherent differences between the groups, the above season-dependent differences suggested that the observed lower semen quality in the sprayers was associated with pesticide spraying work.

Adult↗
PubMed2004

[Susceptibility of Aedes aegypti larvae to the insecticide temephos in the Federal District, Brazil].

OBJECTIVE: To study the susceptibility status of Aedes aegypti to the organophosphate insecticide temephos. METHODS: Samples of Ae. aegypti larvae were obtained, using ovitraps, from eight cities of the Federal District, central Brazil, in 2000 and 2001. Larvae were submitted to the diagnostic dose of 0.012 mg/l temephos, as recommended by standard World Health Organization methodology. Field populations were tested in parallel with reference strains Rockefeller and DIVAL, from the Environmental Surveillance Directory (DIVAL) insectary. The concentration and purity of temephos solutions were verified by gas chromatography. Correlation calculations were performed using StatView - SAS Institute Inc., version 5. Student's t test was used for detecting differences in susceptibility, with significance levels of alpha=0.05. RESULTS: In 2000, Ae. aegypti larvae populations from Taguatinga, Guara, and Nucleo Bandeirante showed resistance to temephos, with mortality ranging from 54.1 to 63.4%. The populations from Gama, Planaltina, and Sobradinho showed altered levels of susceptibility (mortality ranging from 83.6 to 92.8%). The population from Ceilandia was the only susceptible one, with 98% mortality. In 2001, all populations tested were resistant (44.4 to 66.4% mortality). No significant correlation was found between the susceptibility of populations and the distance between the cities of origin, or the amount of insecticide applied in the years preceding the study. CONCLUSIONS: Ae. aegypti susceptibility to temephos is changing in the Federal District. It is essential to continue monitoring the resistance of this vector to insecticides in order to ensure the efficiency of programs aimed at vector control and at the protection of human health.

Aedes↗
PubMed2000

Comparative insecticidal properties of two nucleopolyhedrovirus vectors encoding a similar toxin gene chimer.

Laboratory, greenhouse and field studies were conducted to characterize the insecticidal properties of genetically altered forms of Autographa californica (Speyer) nucleopolyhedrovirus (AcNPV) and Helicoverpa zea (Boddie) NPV (HzNPV) against selected heliothine species. The altered viruses each contained a chimeric 0.8-kb fragment encoding the insect-specific, sodium channel neurotoxin from the Algerian scorpion Androctonus australis Hector (AaIT, hence recombinant viruses designated Ac-AaIT and Hz-AaIT). Based on LD50 values, results from diet-overlay bioassays showed Ac-AaIT and Hz-AaIT to be equally virulent against larval tobacco budworm, Heliothis virescens (F.), but Hz-AaIT averaged 1,335-fold greater bioactivity than Ac-AaIT against larval cotton bollworm, Helicoverpa zea (Boddie). Hz-AaIT killed larvae of both heliothine species at rates significantly faster than those imparted by HzNPV (viral LT50 values averaged 2.5 and 5.6 d, respectively). In greenhouse studies, foliar sprays of Ac-AaIT and Hz-AaIT were equally effective in controlling H. virescens on cotton; however, Hz-AaIT provided control of H. zea on cotton at a level superior to that of Ac-AaIT. For example, after three weekly sessions of foliar application and H. zea artificial infestation, cotton treated with Ac-AaIT or Hz-AaIT at 10 x 10(11) occulsion bodies (OB)/ha averaged 2.5 and 16.2 nondamaged flower buds per plant, respectively. Another greenhouse study conducted against heliothine species on cotton showed that the quicker killing speed exhibited by Hz-AaIT led to improved plant protection versus HzNPV. Finally, results from three field trials demonstrated that Hz-AaIT at 5-12 x 10(11) OB/ha provided control of the heliothine complex in cotton at levels slightly better than Bacillus thuringiensis, equal to the macrolide, spinosad, and only slightly less than that of selected pyrethroid and carbamate insecticides. Overall, results from these studies indicate that, because of host range differences between the two wild-type viruses, HzNPV is the better vectoring agent (versus AcNPV) for designing recombinant clones as insecticides targeted at the multi-species heliothine complex. Further, these studies suggest that if appropriately tailored for the pest complex, recombinant NPVs may be very effective, insect-specific approaches to managing pests in many cropping scenarios. Possible Hz-AaIT deployment strategies for control of heliothine species on conventional and transgenic cotton varieties are discussed.

Animals↗
PubMed2000

Roles of selection intensity, major genes, and minor genes in evolution of insecticide resistance.

A prominent hypothesis about insecticide resistance is that genes of major effect play a key role in field-evolved resistance because the intensity of selection is extremely high in the field. A corollary hypothesis is that the lower intensity of selection in laboratory selection experiments favors polygenic control of insecticide resistance. Contrary to these hypotheses, a literature review revealed that the intensity of selection for insecticide resistance in the field varies widely and overlaps broadly with selection intensities in the laboratory. Also contrary to these hypotheses, results from simulations of population genetic models suggest that selection intensities typical of laboratory selection experiments favor resistance that is conferred by major genes. Major genes dominated responses to selection for resistance across a wide range of simulated selection intensities, with and without fitness costs and refuges. The simulation results also suggest that the intensity of selection, rather than the number of loci conferring resistance, is central in determining rates of resistance evolution and effectiveness of refuges.

Animals↗
PubMed2000

Effect of selected insecticides on the natural enemies Coleomegilla maculata and Hippodamia convergens (Coleoptera: Coccinellidae), Geocoris punctipes (Hemiptera: Lygaeidae), and Bracon mellitor, Cardiochiles nigriceps, and Cotesia marginiventris (Hymenoptera: Braconidae) in cotton.

We evaluated the toxicity of three insecticides (lambda cyhalothrin, spinosad, and S-1812) to the natural enemies Bracon mellitor Say, Cardiochiles nigriceps Viereck, Coleomegilla maculata De Geer, Cotesia marginiventris (Cresson), Geocoris punctipes (Say), and Hippodamia convergens Guérin-Méneville, in topical, residual, and field assays. Lambda cyhalothrin exhibited the greatest toxicity to the natural enemies. In topical toxicity tests, lambda cyhalothrin adversely affected each natural enemy species studied. Residues of lambda cyhalothrin on cotton leaves were toxic to B. mellitor, C. nigriceps, C. maculata, and C. punctipes. Interestingly, residues of this insecticide were not very toxic to C. marginiventris and H. convergens. Geocoris punctipes and C. maculata numbers in the field generally were significantly lower for lambda cyhalothrin treatments than for the other four treatments, substantiating the previous tests. Although cotton aphids began to increase over all treatments around the middle of the test period, the number of cotton aphids in the lambda cyhalothrin plots was significantly higher than the number in any of the other treatments. As cotton aphids increased in lambda cyhalothrin field plots, the predator H. convergens also increased in number, indicating that lambda cyhalothrin did not adversely affect it in accordance with the residual tests. Spinosad exhibited marginal to excellent selectivity, but was highly toxic to each parasitoid species and G. punctipes in topical toxicity tests and to B. mellitor in residual tests. Spinosad generally did not affect the number of G. punctipes, H. convergens, and C. maculata in the field except for one day after the second application for G. punctipes. S-1812 exhibited good to excellent selectivity to the natural enemies. Some reduction of G. punctipes occurred for only a short period after the first and second application of this insecticide in the field. H. convergens and C. maculata were affected very little by S-1812.

Animals↗
PubMed2001

Droplet size and spray volume effects on insecticide deposit and mortality of heliothine (Lepidoptera: Noctuidae) larvae in cotton.

Effects of droplet size and volumetric application rate of tractor-applied lambda cyhalothrin (Karate Z 2.08 SC) on larval tobacco budworm, Heliothis virescens (F.), mortality and insecticide deposition on and within the canopy of mature cotton were explored by use of a laboratory bioassay incorporating field-sprayed cotton and a field trial incorporating natural insect infestations. Insecticide was applied in all combinations of three distinct droplet sizes and three volumetric application rates. Mortality of third-instar tobacco budworm occurring in leaf-disk bioassays was highly correlated with insecticide deposits (microg/leaf disk) at upper- and midcanopy levels. At the upper canopy level, mortality was negatively correlated with volumetric application rate and was not significantly correlated with droplet size. Deposit was negatively correlated with volumetric application rate at the lower plant level and larval mortality decreased with increasing droplet size. Results from this study do not support the recommendations of high volumetric application rates; and although droplet size was less influential than volumetric application rate in deposit and insect mortality, the data indicate a significant trend toward increased midcanopy larval mortality with smaller droplets.

Animals↗
PubMed2002

Pulse-exposure effects of selected insecticides to juvenile Australian crimson-spotted rainbowfish (Melanotaenia duboulayi).

Laboratory toxicity studies were conducted in southeastern Queensland, Australia, to determine the acute lethal effects of a 1-h pulse exposure of selected insecticides to adult and juvenile (<72 h old) crimson-spotted rainbowfish, Melanotaenia duboulayi (Castlenau). In addition, to its ecological significance, this native fish is a predator of mosquitoes. Two organophosphate (OP) compounds (temephos and pirimiphos-methyl), an entomophathogenic bacterium (Bacillus thuringiensis variety israelensis [Bti]) and two insect growth regulators (IGRs) (s-methoprene and pyriproxyfen) were evaluated. Although none of the five insecticides were acutely toxic to adult M. duboulayi under the test conditions, temephos and pirimiphos-methyl were found to be toxic to juveniles, with 24 h pulse exposure LC50 values of 27 and 15 microg/liter (ppb), respectively. Of the two OPs, pirimiphos-methyl was the most toxic, with a lethal dose ratio (pulse exposure LC50 temephos/ pulse exposure LC50 pirimiphos-methyl) of 1.8 (95% CL 0.5-6.4). These pulse exposure LC50 values represented 40 and 4.5% of the estimated environmental concentrations (EEC) for a 15 cm deep water body, respectively. Bti and the two IGRs had no acute toxic effects at up to 10 and 12.5 times the EEC, respectively. Accordingly, in the interests of environmental conservation and integrated pest management (IPM), preference should be given to the latter three insecticides for control of mosquito larvae in juvenile M. duboulayi habitat.

Animals↗
PubMed2002

Proteins as active compounds involved in insecticidal activity of mushroom fruitbodies.

Many mushrooms are toxic to insects. To identify the chemicals involved in insecticidal activity, the toxicity of 14 species has been studied for water solubility, thermolability, and dialysis. The data strongly suggest that proteins are responsible for most of the insecticidal activity of mushroom fruitbodies and may be a source of genes available for plant protection against insects. Among proteins, lectins and hemolysins were good insecticide candidates because the toxicities were not affected by protease.

Agaricales↗
PubMed2002

Binary insecticidal crystal protein from Bacillus thuringiensis, strain PS149B1: effects of individual protein components and mixtures in laboratory bioassays.

A family of novel binary insecticidal crystal proteins, with activity against western corn rootworm, Diabrotica virgifera virgifera LeConte, was identified from Bacillus thuringiensis Berliner. A binary insecticidal crystal protein (bICP) from B. thuringiensis strain PS149B1 is composed of a 14-kDa protein (Cry34Abl) and a 44-kDaprotein (Cry35Ab1). These proteins have been co-expressed in transgenic maize plants, Zea mays L., and effectively control western corn rootworm larvae under field conditions. Laboratory experiments were conducted to better understand the contribution of each component protein to the in vivo activity of the bICP. The 14-kDa protein is active alone against southern corn rootworm, Diabrotica undecimpunctata howardi Barber, and was synergized by the 44-kDa protein. In mixtures, the concentration of the 14-kDa protein had a greater impact on efficacy than the 44-kDa component. Although both proteins are clearly required for maximal insecticidal activity, laboratory results did not support the formation of a stable, fixed-ratio complex of the two component proteins.

Animals↗