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At least 1,063 records · Page 59Linked to original sources
PubMed1996

Comparison of different insecticides and fabrics for anti-mosquito bednets and curtains.

Various formulations of six insecticides (a carbamate and five pyrethroids), were impregnated into bednets and curtains made from cotton, polyester, polyethylene or polypropylene fabric. For bioassays of insecticidal efficacy, female Anopheles gambiae mosquitoes were made to walk on the fabrics for 3 min and mortality was scored after 24 h. The main concentrations tested were: bendiocarb 400 mg/m2, cyfluthrin 30-50 mg/m2, deltamethrin 15-25 mg/m2, etofenprox 200 mg/m2, lambda-cyhalothrin 5-15 mg/m2 and permethrin 200-500 mg/m2. Field trials in Tanzania used experimental huts (fitted with verandah traps) entered by wild free-flying Anopheles gambiae, An.funestus and Culex quinquefasciatus mosquitoes. Results of testing the impregnated fabrics in experimental huts showed better personal protection provided by bednets than by curtains. Permethrin cis:trans isomer ratios 25:75 and 40:60 were equally effective, and the permethrin rate of 200 mg/m2 performed as well as 500 mg/m2. Bioassay data emphasized the prolonged insecticidal efficacy of lambda-cyhalothrin deposits, except on polyethylene netting. Most of the impregnated nets (including the 'Olyset' net with permethrin incorporated during manufacture of the polyethylene fibre) and an untreated intact net performed well in preventing both Anopheles and Culex mosquitoes from feeding on people using them overnight in the experimental huts. Anopheles showed high mortality rates in response to pyrethroid-treated nets, but only bendiocarb treated curtains killed many Culex. Holed nets treated with either cyfluthrin (5 EW formulation applied at the rate of 50 mg a.i./m2) or lambda-cyhalothrin (2.5 CS formulation at 10 mg a.i./m2) performed well after 15 months of domestic use. Treatment with deltamethrin SC or lambda-cyhalothrin CS at the very low rate of 3 mg/m2 gave good results, including after washing and re-treatment.

Animals↗
PubMed1985

Asthma due to insecticide sensitivity.

Two patients are reported in whom asthma was precipitated by exposure to synthetic organophosphorous insecticides. Investigation showed no evidence of systemic poisoning or cholinesterase inhibition and indicated that the asthmatic reactions may have been due to a sensitivity response. The mechanism of this response is unknown but it was inhibited by corticosteroids in one patient. A history of insecticide exposure was obtained from the affected patients only after careful questioning and indicates the need for awareness that sensitivity to insecticides may precipitate asthma and that little exposure is necessary to elicit a response.

Adult↗
PubMed2006

Molecular identification of Bacillus thuringiensis var. israelensis to trace its fate after application as a biological insecticide in wetland ecosystems.

AIMS: To determine the fate of viable Bacillus thuringiensis var. israelensis (Bti) spores dispersed in the environment, using a universally applicable molecular detection methodology. METHODS AND RESULTS: Soil samples were spread on growth medium, after a temperature selection of the spores. A PCR amplification of the cry4Aa and cry4Ba insecticidal genes was applied on the colonies. Ribotyping was performed subsequently. This combined molecular method proved to be very specific for Bti, which was easily differentiated from the other B. thuringiensis serovars. A site regularly treated with Vectobac-G was chosen within the 'Bolle di Magadino' natural reserve, and monitored throughout 1 year for the detection of Bti spores. The results showed that the numbers were relatively high after insecticidal applications (1.4 x 10(5) CFU g(-1)), and decreased approx. 10-fold after 220 days. A successive treatment induced a new increase. CONCLUSIONS: The results show that yearly repeated use of Vectobac-G does not seem to have a major ecological impact on the 'Bolle di Magadino' natural reserve. Bti spores followed a trend leading to their eventual disappearance from the ecosystem, despite the seasonal application of this biological insecticide for more than a decade. SIGNIFICANCE AND IMPACT OF THE STUDY: The molecular identification of Bti cells through the PCR analysis of the delta-endotoxins genes coupled to ribotyping, is an innovative method, that has enabled the identification of this organism into wetland environments.

Bacillus thuringiensis↗
PubMed1992

Characterization of two genes encoding Bacillus thuringiensis insecticidal crystal proteins toxic to Coleoptera species.

Bacillus thuringiensis EG2838 and EG4961 are highly toxic to Colorado potato beetle larvae, and only strain EG4961 is toxic to southern corn rootworm larvae. To investigate the cause of the different insecticidal activities of EG2838 and EG4961, cryIII-type genes toxic to coleopterans were cloned from each strain. The cryIIIB gene, cloned as part of an 8.0-kb EcoRI fragment of EG2838 DNA, encoded a crystal protein (CryIIIB) of 74,237 Da. The cryIIIB2 gene, cloned as part of an 8.3-kb PstI-Asp718 fragment of EG4961 DNA, encoded a crystal protein (CryIIIB2) of 74,393 Da that was 94% identical to CryIIIB. Analysis of the transcriptional start sites showed that cryIIIB and cryIIIB2 were initiated from a conserved region located within 130 nucleotides upstream from the translation start sites of both genes. Although the CryIIIB and CryIIIB2 proteins were similar in sequence, they displayed distinct insecticidal activities: CryIIIB was one-third as toxic as CryIIIB2 to Colorado potato beetle larvae, and CryIIIB2, but not CryIIIB, was toxic to southern corn rootworm larvae. Genes encoding crystal proteins of approximately 32 and 31 kDa were located adjacent to the cryIIIB and cryIIIB2 genes, respectively. The 32- and 31-kDa crystal proteins failed to enhance the insecticidal activities of CryIIIB and CryIIIB2.

Amino Acid Sequence↗
PubMed1997

Cloning of the nprA gene for neutral protease A of Bacillus thuringiensis and effect of in vivo deletion of nprA on insecticidal crystal protein.

The nprA gene, encoding Bacillus thuringiensis neutral protease A, was cloned by the use of gene-specific oligonucleotides. The size of neutral protease A deduced from the nprA sequence was 566 amino acids (60,982 Da). The cloned nprA gene was partially deleted in vitro, and the deleted allele, designated nprA3, was used to construct an nprA3 strain (neutral protease A-deficient strain) of B. thuringiensis. Growth and sporulation of the nprA3 strain were similar to those of an isogenic nprA+ strain, although the extracellular proteolytic activity of the nprA3 strain was significantly less than that of the nprA+ strain. The nprA3 strain produced insecticidal crystal proteins that were more stable than those of the isogenic nprA+ strain after solubilization in vitro, and sporulated cultures of the nprA3 strain contained higher concentrations of full-length insecticidal crystal proteins than did those of its isogenic counterpart. The absence of neutral protease A did not affect the insecticidal activity of a lepidopteran-specific crystal protein of B. thuringiensis. These results indicate that crystal protein stability and yield may be improved by deletion of specific proteases from B. thuringiensis.

Amino Acid Sequence↗
PubMed2001

Toxicity analysis of N- and C-terminus-deleted vegetative insecticidal protein from Bacillus thuringiensis.

A vegetative insecticidal protein (VIP)-encoding gene from a local isolate of Bacillus thuringiensis has been cloned, sequenced, and expressed in Escherichia coli. The expressed protein shows insecticidal activity against several lepidopteran pests but is ineffective against Agrotis ipsilon. Comparison of the amino acid sequence with those of reported VIPs revealed a few differences. Analysis of insecticidal activity with N- and C-terminus deletion mutants suggests a differential mode of action of VIP against different pests.

Animals↗
PubMed1998

Sustainability of transgenic insecticidal cultivars: integrating pest genetics and ecology.

This review examines potential impacts of transgenic cultivars on insect population dynamics and evolution. Experience with classically bred, insecticidal cultivars has demonstrated that a solid understanding of both the target insect's ecology and the cultivar's performance under varied field conditions will be essential for predicting area-wide effects of transgenic cultivars on pest and natural enemy dynamics. This experience has also demonstrated the evolutionary capacity of pests for adaptive response to insecticidal traits in crops. Biochemical and genetic studies of insect adaptation to the Bacillus thuringiensis (Bt) toxins expressed by currently marketed transgenic cultivars indicate a high risk for rapid adaptation if these cultivars are misused. Theoretical and practical issues involved in implementing strategies to delay pest adaptation to insecticidal cultivars are reviewed. Emphasis is placed on examining the "high dose"/refuge strategy that has become the goal of industry and regulatory authorities.

Journal Article↗
PubMed1992

Insecticidal activity and processing in larval gut juices of genetically engineered 130-kDa proteins of Bacillus thuringiensis subsp. aizawai.

The 130-kDa insecticidal protein (IP) of Bacillus thuringiensis subsp. aizawai is proteolytically processed in the gut juice of susceptible insect larvae to yield an insecticidally active 60-kDa fragment. Twenty-seven mutant IP genes with the replacement of codons for Arg and Lys with codons for Gln in the active fragment and its adjacent regions of the 130-kDa IP were constructed by site-directed mutagenesis and expressed in Escherichia coli cells. The produced mutant IPs at Arg87, Arg131, Arg198, Arg311, Arg368, Arg402, Arg458, Arg502, Arg512, Arg524, Arg526, Arg528, and Arg601 had reduced insecticidal activity against Spodoptera litura larvae. The mutant at Arg601 was sensitive to proteolytic digestion in the gut juice of S. litura larvae. Although the mutants at Arg619, Lys622, and Lys637 had nearly the same activity as that of the wild type, the mutant with the triple replacement at Arg619, Lys622, and Lys637 was 2.5 times more active against S. litura larvae than the wild type. This triple mutant showed a slightly different processing profile in the gut juice than that of the wild type.

Amino Acid Sequence↗
PubMed2001

Baseline susceptibility to bacterial insecticides in populations of Culex pipiens complex (Diptera: Culicidae) from California and from the Mediterranean Island of Cyprus.

Bacterial insecticides play an increasingly important role in mosquito control. To establish guidelines for detecting resistance at an early stage, information on natural variation in susceptibility of insect populations to these insecticides is needed. Between 1990 and 1993, the susceptibility of Culex pipiens L. complex to Bacillus thuringiensis subsp. israelensis de Barjac and/or Bacillus sphaericus Neide was determined in 31 collections from California. These collections were undertaken before the widespread use of B. thuringiensis subsp. israelensis and before the registration of B. sphaericus in California. Seven collections from the Mediterranean island of Cyprus, where no microbial insecticides have been used, also were tested. The 1990-1991 California collections exhibited limited variation in susceptibility to B. thuringiensis subsp. israelensis. LC50 and LC95 values spanned about a three-fold and four-fold range, respectively. The 1993 Cyprus collections exhibited both higher mean LC values, and greater variability in those values, than the California collections. The LC50s for the Cyprus collections varied over a 10-fold range, whereas the LC50s varied over a 12.5-fold range. Variation in susceptibility to B. sphaericus among the 1991 California collections was about five-fold at the LC50 and LC95. No significant geographic variation in susceptibility to B. thuringiensis subsp. israelensis was observed among regions within California. Although variation in susceptibility was limited among California collections, the greater variability observed among the Cyprus collections and between the Cyprus and California collections illustrates the importance of establishing regional baselines to monitor accurately for changes in susceptibility.

Animals↗
PubMed2006

Use of residue profile analysis to identify modes of insecticide activity contributing to control of plum curculio in apples.

Residue profile analysis techniques were developed, along with laboratory and field-based bioassays to describe the modes of insecticidal activity responsible for the control of the plum curculio, Conotrachelus nenuphar (Herbst), in apples (Malus spp.). Adult plum curculios were treated in laboratory topical bioassays to determine acute contact activity and lethal time for five insecticides. Azinphosmethyl had the highest levels of toxicity and shortest lethal time values, followed by the neonicotinoids thiacloprid, thiamethoxam, and imidacloprid, whereas indoxacarb had the highest LD50 and LT50 values for topical exposure. Field-based residual activity bioassays assessed adult mortality, and fruit and leaf injury from plum curculio exposed to 4 h, 7 d, and 14 d field-aged residues. All compounds caused significant levels of mortality to plum curculio when adults were exposed to fruit clusters 4 h post-application. Thiacloprid, thiamethoxam, and imidacloprid showed oviposition deterrence, antifeedant, and repellency effects in the 7- and/or 14 d residual bioassays and protected fruit in the absence of significant lethal activity. Indoxacarb maintained lethal activity throughout the study intervals, with the incidence of plum curculio feeding, suggesting that ingestion is an important mode of entry. For the neonicotinoids thiacloprid, thiamethoxam and imidacloprid plum curculio mortality was highly correlated with fruit and leaf surface residues. As surface residues declined, sublethal effects such as oviposition deterrence and antifeedant effect remained. The value of the plant-insect-chemistry triad model for describing the temporal dimensions of insecticidal modes of activity and understanding a compound's critical performance characteristics is discussed.

Animals↗
PubMed1981

Use of insecticide-impregnated ear tags for the control of face flies and horn-flies on pastured cattle.

Three studies were conducted to evaluate the effectiveness of insecticide-impregnated ear tags in controlling face flies, Musca autumnalis DeGeer, and horn flies, Haematobia irritans (Linn.), on pastured beef cattle. In one 16-week trial, polyvinyl chloride (PVC) ear tags treated with stirofos (Rabon) insecticide reduced horn fly numbers by 79% (P less than .05) and face fly numbers by 30% (P less than .05). Coumaphos (Co-Ral) insecticide dust bags used in a separate herd produced an 86% (P less than .05) reduction in horn flies and an 18% (P less than .05) reduction in face flies. In the second study, 5 and 10% permethrin (Atroban), PVC-treated ear tags in a one-piece design were tested. In this 11 week trial, horn fly control averaged 95% (P less than .05) with the 10% tag and 77% (P less than .05) with the 5% tag. Face fly control averaged 49% (P less than .05) for 8 weeks with the 10% permethrin tag. No significant face fly control was achieved with the 5% permethrin tag. In a herd treated with coumaphos dust bags, horn fly control averaged 93% (P less than .05) and face fly control averaged 34% (P less than .05). The third study tested 5 and 10% permethrin, PVC-treated ear tags in a two-piece design and two-piece 5% permethrin-treated ear tags in a polyurethane matrix. Fourteen-week horn fly control averaged 88% (P less than .05) with the 10% PVC-treated tag, 83% (P less than .05) with the 5% PVC-treated tag, 71% (P less than .05) with the 5% polyurethane-treated tag and 74% (P less than .05) with coumaphos dust bags. Face fly control averaged less than 50% (P greater than .05) throughout the trial with all treatments.

Animals↗
PubMed2005

Low pilot exposure to pyrethrin during ultra-low-volume (ULV) aerial insecticide application for control of adult mosquitoes.

Pilot exposure to pyrethrin was monitored after 2 aerial applications of a ultra-low-volume (ULV) pyrethrin insecticide for the control of adult mosquitoes. Pyrethrin exposure was estimated by measuring the excretion in urine of a common metabolite, trans-chrysanthemumdicarboxylic acid, of the natural pyrethrin mixture. Pyrethrin exposure estimated by total daily urine volume was well correlated (R2 = 0.8) with exposure estimated by the creatinine-adjusted volume of combined workday urine voids, indicating that a postapplication spot urine sample would be sufficient to measure pyrethrin exposure. Pilot exposure to pyrethrin was very low after both insecticide applications. The highest exposure was found on day 1, with a dose of 2.05 microg pyrethrin equivalents/day or a dosage of 0.03 microg pyrethrin equivalents/kg/day. These exposure rates represent approximately 1/2,800,000th of the low observed adverse effect level and 1/1,000th of the acceptable daily intake for pyrethrin. The aerial application of ULV pyrethrin insecticide for the control of adult mosquitoes does not result in undue exposure to a pilot who is trained and certified to conduct such control operations.

Aircraft↗
PubMed1986

Differences in the in vivo and in vitro effects of the carbamate insecticide, carbaryl on rat hepatic monooxygenases.

The effects of one of the most widely used insecticides, carbaryl, on the hepatic cytochrome P-450-dependent monooxygenases were determined. Addition of carbaryl to liver microsomes from untreated or phenobarbital (PB)-pretreated rats resulted in a weak Type I binding spectrum. A much stronger spectral Type I interaction was observed when microsomes from 3-methylcholanthrene(3-MC)-treated rats were used. In vitro, carbaryl caused marked inhibition of ethylmorphine and benzphetamine N-demethylases, benzo(a)pyrene hydroxylase, 7-ethoxycoumarin and 7-ethoxyresorufin O-deethylase in liver microsomes. Kinetic studies demonstrated that carbaryl was a competitive inhibitor of ethylmorphine N-demethylase activity. Daily administration of carbaryl for 4 days by gavage or intraperitoneally resulted in no significant alterations in hepatic cytochrome P-450 levels, ethylmorphine N-demethylase or benzo(a)-pyrene hydroxylase activities. The lack of effect of carbaryl in vivo may be due to the rapid metabolism of the insecticide, such that the insecticide may not be present in the liver endoplasmic reticulum to cause the inhibitory effects observed in vitro.

Animals↗
PubMed1970

[Susceptibility Of Cockroaches (Blattella Germanica Linneaus) To Various Insecticides]

During the period from May to October 1969, the authors carried out a series of tests with the aim to ascertain the present status of susceptibility of adult cockraoches to various insecticides. The tests on the susceptibility of cockroaches to dieldrin, D.D.V.P., Diazinon; Dibrom, Malathion and lindane were performed with the topical application and the residual film methods under the conditions of 26 degrees C and 80% of relative humidity. The insects tested were collected from Seoul City and were reared at the laboratory. Some of the important results so far obtained can be summarized as follows: 1. The median lethal doses (LD-(50)) of the five insecticides against female adult cockroaches were: 0.4 microgram/roach or 4.02 microgram/body weight (gm) by Dieldrin, 0.29/roach or 2.88 microgram/body weight (gm) by D.D.V.P., 0.29 microgram/roach or 2.96 microgram/body weight (gm) by Diazinon, 0.54 microgram/roach or 5.37 microgram/body weight (gm) by Dibrom, and 2.96 microgram/roach or 29.60 microgram/body weight (gm) by Malathion. And those against male adult cockroaches were: 0.18 microgram/roach or 3.29 microgram/body weight (gm) by Dieldrin, 0.27 microgram/roach or 4.89 microgram/body weight (gm) by D.D.V.P., 0.16 microgram/roach or 2.91 microgram/body weight (gm) by Diazinon, 0.49 microgram/roach or 8.97 microgram/body weight (gm) by Dibrom, and 1.32 microgram/roach or 24.19 microgram/body weight (gm) by Malathion. 2. The level of susceptibility of adult cockroaches to the insecticides tested was 1.0-1.6 times higher as compared with the results obtained on the Japanese Takashi strain. 3. The median knockdown times (LT-(50)) of the female adult cockroaches by insectcides at 1% concentration of 3 mg per square centimetre were 1.82 hours by Malathion, 1.36 hours by Diazinon, 0.56 hours by Lindane, 0.50 hours by Dibrom, and 2.56 hours by D.D.V.P. 4. Amarked difference was seen to exist between the males and the females. The female cockroaches were more resistant than the male to Dieldrin, Diazinon and Malathion.

Journal Article↗
PubMed2000

Isolation and insecticidal effects of some bacteria from Euproctis chrysorrhoea L. (Lepidoptera: Lymantriidae).

In this study, we investigated the bacterial pathogens of Euproctis chrysorrhoea and tested for their insecticidal activities. Based on colony color and morphology, four isolates were determined. According to morphological, physiological and biochemical characters of the isolates, they were identified as Enterobacter aerogenes, Lactobacillus sp., Bacillus thuringiensis and Micrococcus luteus. The insecticidal effects of these bacterial isolates on third-fourth instar larvae of Euproctis chrysorrhoea were investigated. The highest insecticidal effect determined on this pest is 68% with Bacillus thuringiensis. The effects of the other isolates are 45% with Enterobacter aerogenes, 15% Micrococcus luteus and 0% with Lactobacillus sp.

Animals↗
PubMed1999

CYP6B2 Expression in Insecticide-Resistant and -Suspcitible Strains of Helicoverpa armigera.

A fragment of CYP6B2 gene was obtained from the midgut cDNA library of the fifth instar larvae of the ballworm (Helicoverpa armigera) with RT-PCR. The product of 627 bp was cloned and sequenced. The results of dot blotting analysis of mRNA proved that CYP6B2 is expressed at higher level (mRNA) in an insecticide-resistant strain than in a susceptible strain, showing that the regulation was at transcription level. The mRNA is induced by pyrethroid in susceptible, but not in the insecticide-resistant strains. We guess that mutation in the 5' upstream regulator of the insecticide-resistant strain may lead to the difference in the expression level between resistant and susceptible strains.

Journal Article↗
PubMed1992

Pathological changes in testes and liver of male albino rats after dermal exposure to DDVP insecticide.

Exposure of male albino rats to DDVP insecticide at sublethal dose of 30 mg/kg/day through dermal painting for a period of 90 days didn't show any intoxication symptoms or mortality. However, cytopathological changes in testicular and liver tissues were evident. There was a positive correlation between the degree of cellular damage and the period of insecticide administration. In general, damages were prominent in rats treated for 30 days or more. Histological examination of testes showed degenerative seminiferous tubules and fewer leydig cells. Hepatic cells were congested, atrophied and showed different stages of necrobiotic changes. This suggests a great care and caution for workers during different phases of DDVP insecticide handling.

Administration, Topical↗
PubMedDate not supplied

Determination of the residues of eleven organophosphorus insecticides in Job's-tears by gas chromatography with a nitrogen-phosphorus detector.

A simplified method for determining 11 organophosphorus insecticides (dichlorvos, methamidophos, acephate, diazinon, dimethoate, chlorpyrifos, malathion, parathion, quinalphos, methidathion, and ethion) in the Chinese herbal medicine Job's-tears is described. Standards were fortified into Job's-tears (5 g) at 4 levels. The organophosphorus insecticides were extracted with dichloromethane and cleaned up with a mixture of Celite 545-activated carbon (4 + 1). The extracts were analyzed by gas chromatography using a nitrogen-phosphorus detector. Analysis of fortified Job's-tears shows average recoveries ranged from 73.90-98.70%, 86.31-93.15%, 84.92-96.22%, and 83.29-104.23% at 0.05, 0.1, 0.5, and 1.0 mg/kg levels, respectively. The minimum detectable amount ranged from 1.0 x 10(-10) to 5.0 x 10(-10) g, and the limit of quantitation for the method was 0.05 mg/kg. The method is rapid, simple, sensitive, reproducible, and applicable to the determination of these 11 organophosphorus insecticides in Job's-tears.

Chromatography, Gas↗