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[Degradation of the insecticide parathion in soil].

Degradation of the insecticide Parathion in four types of soil from the Northeast of Brazil has been studied using radiometric techniques. In all the soil samples, sterilized or not, metabolites were detected with Rf values of 0.00 and 0.17 respectively--Silica Gel 60 F254 tlc plates (Merck); solvent system: hexane-acetone (4:1, v/v)--. However, 14CO2 was formed only with the non-sterilized soils and this was independent of the use or not of organic fertilizer. These results suggest that the two metabolites, mentioned above, are formed by a predominantly non-biological pathway, where as the formation of carbon dioxide requires the participation of the microbial flora of the soil. Analysis of the interaction of 14C-Parathion with soils shows that the extent of degradation of this insecticide is modified by adsorption on the soil particles.

Adsorption↗

Insecticide poisoning of peafowls and lead poisoning in a cockatoo.

The deaths of peafowls and a cockatoo were respectively traced to insecticide and lead toxicities. The specific insecticide could not be identified but was demonstrated in the liver by use of fruit flies. The liver of the cockatoo contained 7.1 ppm of lead. The source was presumably a plastic feeder painted with a leaded paint.

Animals↗

Some physical, chemical, and insecticidal properties of some O, O-dialkyl )-(3,5,6-trichloro-2-pyridyl) phosphates and phosphorothioates.

Large differences have been observed between the physical, chemical, and insecticidal properties of four representatives of a closely related series of O,O-dialkyl O-(3,5,6-trichloro-2-pyridyl) phosphates and phosphorothioates. These differences are important in explaining large variations in the persistence of the compounds and in their toxicity for insects that arise from the use of different test methods and formulations, representing various uses of the insecticides.

Animals↗

Comparative insecticidal acitvity of sumithrin and neopinamine.

The examination of insecticidal properties of the new pyrethroid--sumithrin--showed this compound in contact action to be a highly effective insecticide, superior in activity to neopinamine. The intestinal action of sumithrin is less pronounced in comparison with neopinamine. Sumithrin is more selective in its effect on insects as compared with neopinamine. In the form of earosols, sumithrin and its mixtures with DDVP are less active than compositions based on neopinamine.

Animals↗

The interaction of the phosphorothioate insecticides chlorpyrifos and parathion and their oxygen analogues with bovine serum albumin.

The distribution and subsequent toxicity of hazardous chemicals can be influenced by their interactions with plasma proteins. In the present study reversible binding of the phosphorothioate insecticides chlorpyrifos and parathion to fatty acid-free bovine serum albumin (BSA) was examined using the technique of equilibrium dialysis. Computer analyses of the binding data revealed that chlorpyrifos and parathion each bound reversibly to a single class of binding sites on BSA, with apparent KD values of 3.4 +/- 0.1 and 11.1 +/- 0.3 microM, respectively. Additionally, the maximal number of binding sites for each insecticide per molecule of BSA was one. Displacement studies using both chlorpyrifos and parathion indicated that each was a competitive inhibitor of the other's binding, suggesting that they were bound to the same site. Incubation of chlorpyrifos oxon or paraoxon with a 1% solution of BSA resulted in limited, EDTA-insensitive formation of 3,5,6-trichloro-2-pyridinol or p-nitrophenol, respectively. Pretreatment of BSA with 5 mM paraoxon, chlorpyrifos oxon, or 1 mM diisopropylfluorophosphate did not alter this activity, suggesting that these reactions resulted from an esterase-like capacity of BSA, and not from phosphorylation of BSA by these oxons.

Animals↗

Use of granulated fertilizers with Actellic EC 50 insecticide in the control of mosquito larvae.

Granulated fertilizers [ammonium nitrate, synthetic fertilizer] were used as carriers to prepare an insecticide granulate suitable for the control of Aedes cantans and Aedes vexans mosquito larvae under field conditions. The insecticide granulate was obtained by mixing 1 volume unit of Actellic EC 50 with 50 volume units of fertilizer. The optimal dose required to ensure and effective control of Aedes mosquito larvae was 2--5 g of granulate per 1 m3 of water [i.e. 2--5 kg/ha per each 1- cm depth of water] in hatching areas with a relatively clean water or during periods of slow larval growth and development, and 10 g of granulate per 1 m3 of water for hatching places polluted with organic substances or for periods of accelerated larval growth during summer months. The described Actellic EC 50 application practice ensures a complete survival of numerous non-target water organisms, including Tubifex species, Rhynchelmis species, molluscs, flatworms [Turbellaria], Asellus aquaticus, water mites [Hydrachna sp.] water striders (Gerris lacustris] and Dixella species larvae].

Aedes↗

Effect of the carbamate insecticide Sevin on Anabaena sp. and Westiellopsis prolifica.

Effect of the insecticide Sevin (50% w/v) was examined on survival, growth and nitrogen fixation of two filamentous blue-green algae, Anabaena sp. and Westiellopsis prolifica. Lower concentration of the insecticide (10 micrograms/ml) increased survival, growth and nitrogen fixation while higher concentrations showed an inhibitory effect.

Carbaryl↗

Efficacy of propoxur insecticide strip use in a laboratory animal facility.

A non-fumigant, controlled-release, impregnated strip (insecticide strip) was evaluated for effectiveness against cockroaches (Blatella germanica) in a conventional animal facility. A substantial initial roach mortality was observed in treated rooms. Continued use of the insecticide strip assisted in the control of the cockroach population and did not affect plasma cholinesterase levels of exposed laboratory animals.

Animals↗

The future of microbial insecticides as vector control agents.

Insect vectors of human diseases are subject to diseases of their own caused by viruses, bacteria, fungi, protozoans, and nematodes. Over the past 30 years, many members of these groups have been evaluated as vector control agents, particularly for mosquito control. Most pathogens and nematodes occur primarily in larvae, and are only effective against this stage. The principal candidate control agents studied include iridescent and nuclear polyhedrosis viruses, the bacteria Bacillus thuringiensis and Bacillus sphaericus, the fungi Lagenidium giganteum, Culicinomyces clavosporus, and species of the genus Coelomomyces, the protozoan Nosema algerae, and the mermithid nematode Romanomermis culicivorax. Of these, the only one considered an operational success is the bacterium, Bacillus thuringiensis subsp. israelensis (B.t.i.), which has proven useful for control of both mosquito and blackfly larvae in programs where larviciding has been traditionally employed as a vector control tactic. The reasons for the success of B.t.i. are its cost-effectiveness and relative ease of use, which are due, respectively, to the ability of B.t.i. to be grown on artificial media and the development of formulations that can be applied using conventional insecticide application technology. Because few microbial insecticides are cost-effective, and those that are are only effective against larvae, these agents will likely play only a minor, but in some cases important, role in most future vector control programs.

Animals↗

[Insecticidal gels--a promising form for using pyrethroids].

Insecticidal gels containing the following agents as active ingredients: permethrin (0.4%), cipermethrin (0.1%), fenvalerate (0.5%), alpha-methrin (0.2%) were designed and studied under laboratory and field conditions. When applied to various surface types, the designed formulations of the gels caused 100% death of cockroaches, domestic flies, bed-bugs and fleas. The application rate is 2.5-10.0 g/m2 depending on the species of insects. The residual insecticidal action of gels on the surfaces is as long as 3 months. The designed formulations are approved by the Ministry of Health of Russia for their manufacture and application.

Animals↗

Interaction of organophosphorus insecticides phosphamidon & malathion on lipid profile & acetylcholinesterase activity in human erythrocyte membrane.

The organophosphorus insecticides phosphamidon and malathion were found to inhibit the activity of human acetylcholinesterase in vitro, in the human erythrocyte membrane. Lineweaver-Burk analysis indicated that the insecticide induced inhibition of acetylcholinesterase activity was uncompetitive in nature. The total lipid, cholesterol and phospholipid contents of erythrocyte membranes were reduced following phosphamidon and technical malathion treatment, while the level of lipid peroxidation was raised following malathion treatment.

Acetylcholinesterase↗

Studies on insecticide resistance in anopheline mosquitos.

This paper describes observations made both on laboratory colonies in London and on wild-caught material in the field of insecticide-susceptible and -resistant strains of A. gambiae, A. sundaicus and A. stephensi. The techniques used in assessing the susceptibilities of both larvae and adults are described and the effects of species, rearing, age, sex, feeding and ovarian development on susceptibility are discussed. The effect of continued selection by DDT in the laboratory of a presumably homogeneous susceptible strain of A. stephensi is then outlined and the phenomenon of "vigour tolerance" demonstrated.Specific, monofactorially-inherited resistance is then described as witnessed with A. gambiae and A. sundaicus. A. gambiae shows a high degree of resistance to dieldrin and cross-resistance to the related cyclodiene compounds and gamma-BHC, but remains susceptible to DDT. Resistance is due to a single gene, partially dominant, the hybrid showing a moderate degree of resistance. A. sundaicus shows a moderate degree of resistance to DDT and cross-resistance to DDT analogues, but remains susceptible to dieldrin and gamma-BHC. Resistance is again due to a single gene but here it is virtually recessive and the hybrid is to all intents and purposes susceptible. The discriminating dosage technique for distinguishing the phenotypes in these species is described.Resistance in other anophelines and in houseflies is discussed and suggestions made as to methods of detecting anopheline resistance in the field.

Animals↗

Resistance and cross-resistance to neonicotinoid insecticides and spinosad in the Colorado potato beetle, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae).

The Colorado potato beetle, Leptinotarsa decemlineata (Say), has developed resistance to many insecticides used for its control, recently including imidacloprid, a neonicotinoid compound. Other neonicotinoids are now being deployed to control this pest. A key point in the strategies of resistance management is the monitoring of resistance and cross-resistance. In the summer of 2003, imidacloprid-resistant adult Colorado potato beetles collected from Long Island, New York, USA were bioassayed using topical applications of imidacloprid and nine other neonicotinoids. Compared to a standard susceptible strain, the Long Island beetles showed 309-fold resistance to imidacloprid, and lower levels of cross-resistance to all other neonicotinoids, despite these never having been used in the field, i.e., 59-fold to dinotefuran, 33-fold to clothianidin, 29-fold to acetamiprid, 28-fold to N-methylimidacloprid, 25-fold to thiacloprid, 15-fold to thiamethoxam, 10-fold to nitenpyram, but less than 2-fold to nicotine. In injection bioassays, high resistance to imidacloprid was also found (116-fold). Piperonyl butoxide partially suppressed resistance to imidacloprid, but the resistance level was still over 100-fold, indicating that other mechanisms were primarily responsible for resistance. Low levels of resistance (8- to 10-fold) were found to the nicotinic activator, spinosad, in an imidacloprid-resistant strain collected from the same field in 2004. The cross-resistance seen with all the neonicotinoids tested suggests that the rotation of imidacloprid with other neonicotinoids may not be an effective long-term resistance management strategy. Rotation with spinosad also carries some risk, but it is unlikely that spinosad resistance in this case is mechanistically related to that for the neonicotinoids.

Anabasine↗

New developments in insecticide resistance in the glasshouse whitefly (Trialeurodes vaporariorum) and the two-spotted spider mite (Tetranychus urticae) in the UK.

A recent survey of insecticide resistance in two of the most problematic pests in UK glasshouses revealed some new developments. At least some individuals in all UK samples of Trialeurodes vaporariorum that were tested resisted the insect growth regulator (IGR) buprofezin. The most strongly resistant strains were unaffected by the field application rate of this compound, and even samples from populations that had never been exposed to buprofezin contained individuals that survived the highest concentration applied (10,000 mg litre-1). The field rate of buprofezin was shown to select for resistance through vapour action alone. The benzophenylurea teflubenzuron, an unrelated IGR, was cross-resisted by buprofezin-resistant individuals. There was no evidence of resistance to imidacloprid, but all T vaporariorum strains tested, regardless of origin, exhibited a high innate tolerance to nicotine, when compared with another whitefly species, Bemisia tabaci. Marked resistance to fenbutatin oxide and tebufenpyrad was found in single glasshouse populations of Tetranychus urticae, but these compounds and abamectin appeared to remain highly effective against all other strains collected.

Acari↗

Amplified esterase genes and their relationship with other insecticide resistance mechanisms in English field populations of the aphid, Myzus persicae (Sulzer).

Myzus persicae samples were collected from populations present on a range of field crops between 1997 and 2000. A combination of biochemical, DNA-based diagnostics and bioassays was used to assess the presence of three insecticide resistance mechanisms: elevated carboxylesterase (E4 or FE4), insensitive acetylcholinesterase and insensitive sodium channels (knockdown resistance, kdr). For the carboxylesterases, both the levels of enzyme and the type of gene present (E4 or FE4) were determined. The results showed that during the time period studied there was a dramatic reduction in the proportion of aphids with very high levels of E4 and an increase in those with lower levels of FE4. There was also a slightly different E4 gene present in a limited number of samples. The change in esterase genes was accompanied by a virtual loss of the insensitive AChE variant and a maintenance of aphids with kdr. The selection pressures and other factors leading to these changes in field populations of M persicae are discussed.

Acetylcholinesterase↗

Mechanisms of resistance to organophosphorus insecticides in populations of the obliquebanded leafroller Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae) from southern Ontario.

Populations of Choristoneura rosaceana (Harris) from orchards in Ontario were shown to be resistant to azinphos-methyl and to other types of organophosphorus insecticides. Resistance extended to methyl carbamates and to methomyl. The laboratory population used for these assays and selected with azinphosmethyl was also resistant to the pyrethroid, cypermethrin. Resistance was associated with increased esterase activity and was reduced by the addition of the synergist DEF. IEF studies of esterases also indicated increased activity in resistant populations, but did not identify any unique esterases associated with the resistance. Resistance was highly correlated (r = 0.78) with elevated esterases but not with increased glutathione-S transferase activity (r = 0.13). Other mechanisms did not appear to be related.

Animals↗

Insecticide resistance in Egyptian populations of the cotton whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae).

Three collections of Bemisia tabaci were taken from cotton and vegetable crops at the beginning of the growing season in Egypt. These displayed marked resistance to the carbamates carbosulfan (ca 20- to 50-fold) and aldicarb (ca 40- to 80-fold) and moderate resistance to the pyrethroids cypermethrin (ca 10- to 30-fold) and lambda-cyhalothrin (ca 10- to 25-fold). They displayed no resistance to the organophosphates profenofos and pirimiphos-methyl, or to imidacloprid. Another population, collected at the end of the growing season, differed markedly in its response. In this population, resistance to carbosulfan remained high (ca 40-fold), resistance to profenofos and cypermethrin was increased (ca 20- and 50-fold respectively) and a slight resistance to imidacloprid was detected (ca 6-fold). Resistance to cypermethrin and profenofos was shown to be similar among adults and nymphs. Irrespective of collection date, none of the populations showed resistance to pyriproxyfen. These Egyptian populations were compared with two representative Israeli populations. The differences between their resistance profiles is discussed in terms of their collection date, their geographical proximity and the patterns of insecticide use at their sites of collection.

Animals↗

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